Sound Pressure Level

Measurements on the inverse filtered airflow waveform and of estimated average transglottal pressure and glottal airflow were made from syllable sequences in low, normal, and high pitch for 25 male and 20 female speakers. Correlation analyses indicated that several of the airflow measurements were more directly related to voice intensity than to fundamental frequency (Fo). Results suggested that pressure may have different influences in low and high pitch in this speech task. It is suggested that unexpected results of increased pressure in low pitch were related to maintaining voice quality, that is, avoiding vocal fry. In high pitch, the increased pressure may serve to maintain vocal fold vibration. The findings suggested different underlying laryngeal mechanisms and vocal adjustments for increasing and decreasing F o from normal pitch. Key Words: Inverse filter--Transglottal air pressure--Glottal airflow--Pitch--Male and female speakers.

A computational model was developed to simulate the responses of auditory-nerve ͑AN͒ fibers in cat. The model's signal path consisted of a time-varying bandpass filter; the bandwidth and gain of the signal path were controlled by a nonlinear feed-forward control path. This model produced realistic response features to several stimuli, including pure tones, two-tone combinations, wideband noise, and clicks. Instantaneous frequency glides in the reverse-correlation ͑revcor͒ function of the model's response to broadband noise were achieved by carefully restricting the locations of the poles and zeros of the bandpass filter. The pole locations were continuously varied as a function of time by the control signal to change the gain and bandwidth of the signal path, but the instantaneous frequency profile in the revcor function was independent of sound pressure level, consistent with physiological data. In addition, this model has other important properties, such as nonlinear compression, two-tone suppression, and reasonable Q 10 values for tuning curves. The incorporation of both the level-independent frequency glide and the level-dependent compressive nonlinearity into a phenomenological model for the AN was the primary focus of this work. The ability of this model to process arbitrary sound inputs makes it a useful tool for studying peripheral auditory processing.

Cutting tool wear degrades the product quality in manufacturing processes. Monitoring tool wear value online is therefore needed to prevent degradation in machining quality. Unfortunately there is no direct way of measuring the tool wear online. Therefore one has to adopt an indirect method wherein the tool wear is estimated from several sensors measuring related process variables. In this work, a neural network-based sensor fusion model has been developed for tool condition monitoring (TCM). Features extracted from a number of machining zone signals, namely cutting forces, spindle vibration, spindle current, and sound pressure level have been fused to estimate the average flank wear of the main cutting edge. Novel strategies such as, signal level segmentation for temporal registration, feature space filtering, outlier removal, and estimation space filtering have been proposed. The proposed approach has been validated by both laboratory and industrial implementations. r

We tested the ability of birds to detect and discriminate natural vocal signals in the presence of masking noise using operant conditioning. Masked thresholds were measured for budgerigars, Melopsittacus undulatus, and zebra finches, Taeniopygia guttata, on natural contact calls of budgerigars, zebra finches and canaries, Serinus canaria. Thresholds increased with increasing call bandwidth, the presence of amplitude modulation and high rates of frequency modulation in calls. As expected, detection thresholds increased monotonically with background noise level. Call detection thresholds varied with the spectral shape of noise. Vocal signals were masked predominantly by noise energy in the spectral region of the signals and not by energy at spectral regions remote from the signals. In all cases, thresholds for discrimination between calls of the same species were higher than thresholds for detection of those calls. Our data provide the first opportunity to estimate distances over which specific communication signals may be effective (i.e. their 'active space') using masked thresholds for the signals themselves. Our results suggest that measures of peak sound pressure level, combined with the spectrum level of noise within the frequency channel having the greatest signal power relative to background noise, give the most similar results for estimating a signal's maximum communication distance across a variety of sounds. We provide a simple model for estimating likely detection and discrimination distances for the signals tested here.

that some RD subjects (six out of 30) had impaired magnocellular function. Nevertheless, these RD subjects were also consistently impaired on a broad range of other perceptual tasks. The performance of the other subgroup of RD subjects on magnocellular tasks did not differ from that of controls. However, they did show impaired performance in both visual and auditory nonmagnocellular tasks requiring ®ne frequency discriminations. The stimuli used in these tasks were neither modulated in time nor brie¯y presented. We conclude that some RD subjects have generally impaired perceptual skills. Many RD subjects have more speci®c perceptual de®cits; however, the`magnocellular' level of description did not capture the nature of the perceptual dif®culties in any of the RD individuals assessed by us.

Generation of a strong electrical potential in the cochlea is uniquely mammalian and may reflect recent evolutionary advances in cellular voltage-dependent amplifiers. This endocochlear potential is hypothesized to dramatically improve hearing sensitivity, a concept that is difficult to explore experimentally, because manipulating cochlear function frequently causes rapid degenerative changes early in development. Here, we examine the deafness phenotype in adult Claudin 11-null mice, which lack the basal cell tight junctions that give rise to the intrastrial compartment and find little evidence of cochlear pathology. Potassium ion recycling is normal in these mutants, but endocochlear potentials were below 30 mV and hearing thresholds were elevated 50 dB sound pressure level across the frequency spectrum. Together, these data demonstrate the central importance of basal cell tight junctions in the stria vascularis and directly verify the two-cell hypothesis for generation of endocochlear potential. Furthermore, these data indicate that endocochlear potential is an essential component of the power source for the mammalian cochlear amplifier.

Absolute and frequency-difference thresholds were determined by the conditioned-suppression technique. The results show that the average frequency range of audibility at +50 dB sound-pressure level extends from 86 Hz to 46.5 kHz, with a best frequency near 8 kHz. Individual differences in sensitivity are related to body weight and, probably, age. The average frequency-difference 1/men is 3.5% from 125 I-Iz to 42 kHz. Compared to other mammals, the auditory capacities of guinea pig are within one standard deviation of the mammalian mean on each of six dimensions: high-frequency and low-frequency cutoff, lowest intensity, best frequency, area of the audible field, and frequency discrimination. 1888 Volume 49 Number 6 (Part 2) 1971 attained, a tone was presented for 10 sec and, at its offset, a shock was delivered to the guinea pig's feet (Fig. 1). This conditioning procedure soon resulted in a cessation of licking at the onset of a tone. In test trials, this cessation, or suppression, of licking was used as evidence that a tone had been perceived. A. Subjects Four domestic guinea pigs (Cavia procellus) were used. Guinea pigs A and B were judged to be adolescents on the basis of their body weight at the beginning of the experiment, while C and D were both adults. They were maintained on a diet of rabbit pellets (Flint River Mills) supplemented with vitamins (Vimtone) and, occa-sionaNy, fruit and greens. B. Details of Behavioral Apparatus The animals were tested in a rectangular cage 7 in. long, 6 in. high, and 6 in. wide. The walls, ceiling, and SAFE ß. SA SIGNAL WARNING SIGNAL SIGNAL IO SEC SHOCK Fro. 1. Stimulus configuration in absolute threshold test. Duration of "safe" signal (silence) varied randomly from 15 to 600 sec.

The purpose of this investigation was to study voice changes during a working day. The subjects consisted of 33 female primary and secondary schoolteachers who recorded their first and last lessons during one school day. The subjects were studied both as one group and two subgroups (those with many and those with few voice complaints). Estimates of fundamental frequency (F 0), sound pressure level (SPL), the standard deviations of these values (F 0 SD; SPL SD) and F 0 time (vibration time of vocal folds) were made. The most obvious change due to loading was the rise of F 0 that was 9.7 Hz between the first and last lesson (P = 0.00). F 0 increased more (12.8. Hz, P = 0.006) in the subgroup with few complaints.

Traffic-generated air pollution and noise have both been linked to cardiovascular morbidity. Since traffic is a shared source, there is potential for correlated exposures that may lead to confounding in epidemiologic studies. As part of the Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air), 2-week NO and NO 2 concentrations were measured at up to 105 locations, selected primarily to characterize gradients near major roads, in each of 9 US communities. We measured 5-min A-weighted equivalent continuous sound pressure levels (L eq ) and ultrafine particle (UFP) counts at a subset of these NO/NO 2 monitoring locations in Chicago, IL (N = 69 in December 2006; N = 36 in April 2007) and Riverside County, CA (N = 46 in April 2007). L eq and UFP were measured during non-"rush hour" periods (10:00-16:00) to maximize comparability between measurements. We evaluated roadway proximity exposure surrogates in relation to the measured levels, estimated noise-air pollution correlation coefficients, and evaluated the impact of regionalscale pollution gradients, wind direction, and roadway proximity on the correlations. Five-minute L eq measurements in December 2006 and April 2007 were highly correlated (r = 0.84), and measurements made at different times of day were similar (coefficients of variation: 0.5-13%), indicating that 5-min measurements are representative of long-term L eq . Binary and continuous roadway proximity metrics characterized L eq as well or better than NO or NO 2 . We found strong regional-scale gradients in NO and NO 2 , particularly in Chicago, but only weak regional-scale gradients in L eq and UFP. L eq was most consistently correlated with NO, but the correlations were moderate (0.20-0.60). After removing the influence of regional-scale gradients the correlations generally increased (L eq -NO: r = 0.49-0.62), and correlations downwind of major roads (L eq -NO: r = 0.53-0.74) were consistently higher than those upwind (0.35-0.65). There was not a consistent effect of roadway proximity on the correlations. In conclusion, roadway proximity variables are not unique exposure surrogates in studies of endpoints hypothesized to be related to both air pollution and noise. Moderate correlations between traffic-generated air pollution and noise suggest the possibility of confounding, which might be minimized by considering regional pollution gradients and/or prevailing wind direction(s) in epidemiologic studies. ☆

The ear is a remarkably sensitive pressure fluctuation detector. In guinea pigs, behavioral measurements indicate a minimum detectable sound pressure of ~20 μPa at 16 kHz. Such faint sounds produce 0.1 nm basilar membrane displacements, a distance smaller than conformational transitions in ion channels. It seems that noise within the auditory system would swamp such tiny motions, making weak sounds imperceptible. Here, a new mechanism contributing to a resolution of this problem is proposed and validated through direct measurement. We hypothesize that vibration at the apical end of hair cells is enhanced compared to the commonly measured basilar membrane side. Using in vivo optical coherence tomography, we demonstrated that apical-side vibrations peak at a higher frequency, had different timing, and were enhanced compared to the basilar membrane. These effects depend nonlinearly on the stimulus level. The timing difference and enhancement are important for explaining how the noise problem is circumvented.

Amplitude and phase of steady-state signals recorded in response to amplitude-modulated (AM) sine tones vary over time, suggesting that the steady-state response (SSR) reflects not only stimulus input but also its interaction with other input streams or internally generated signals. Alterations of the interaction between simultaneous SSRs associated with tinnitus were studied by recording the magnetic field evoked by AM-tones with one of three carrier and one of three modulation frequencies. Single AM-tones were presented in single presentation mode and superpositions of three AM-tones differing in carrier and modulation frequency in multiple presentation mode. Modulation frequency-specific SSR components were recovered by bandpass filtering. Compared with single mode, in multiple mode SSR amplitude was reduced in healthy controls, but increased in tinnitus patients. Thus, while in controls multiple response components seem to reciprocally inhibit one another, in tinnitus reciprocal facilitation seems to predominate. Reciprocal inhibition was unrelated to the phase coherence among SSR components, but was correlated with the frequency of phase slips, indicating that the lateral interaction among SSR components acts in a quasi-paroxysmal manner and manifests itself in terms of a random train of phase reset events. Phase slips were more frequent in patients than controls both in single and multiple mode. Together, these findings indicate that lateral or surround inhibition of single units in auditory cortex is reduced and suggest that in-field inhibition is increased in tinnitus.

Exact locations of spawning areas used by marine fishes are needed to design marine reserves and estimate spawning stocks. The location of spawning areas of soniferous fishes such as weakfish Cynoscion regalis can be determined by means of passive hydroacoustic surveys. We conducted nocturnal hydrophone surveys at 12 locations in Pamlico Sound in May of 1996 and 1997. Digital audio tapes were made of weakfish “purring” sounds, the tapes were analyzed spectrographically and compared with ichthyoplankton surveys taken at the same stations and times. All weakfish “purring” sounds were recorded at stations near inlets. Maximum sound pressure levels recorded after sunset were 127 dB (re 1 (μPa) for individual weakfish, but reached a maximum of 147 dB when weakfish and other fish were producing sounds simultaneously. The maximum distance that an individual weakfish “purr” can be detected above the background sound, assuming a cylindrical spreading model, is approximately 50 m. There was a strong association (r = 0.78) between the log10— transformed abundance of early-stage sciaenid-type eggs and maximum sound pressure levels, with the greatest numbers occurring at the inlet stations. These results suggest that passive hydroacoustic surveys can be used to delimit spawning areas for conservation and management purposes.

This paper presents some preliminary observations on sound-assisted fluidization of hydrophobic fumed silica nanoparticles (Degussa AerosilR R974, having a primary particle size of 12 nm) in the form of large 100 -400 Am agglomerates. The effect of sound on the fluidization behavior of the nanoparticle agglomerates, including the fluidization regime, the minimum fluidization velocity, the bed pressure drop and the bed expansion has been investigated. It is shown that, with the aid of sound wave excitation at low frequencies, the bed of nanoparticle agglomerates can be readily fluidized and the minimum fluidization velocity is significantly reduced. For example, the minimum fluidization velocity is decreased from 0.14 cm/s in the absence of sound excitation to 0.054 cm/s with the assistance of the sound. In addition, under the influence of sound, channeling or slugging of the bed quickly disappears and the bed expands uniformly. Within a certain range of the sound frequency, typically from 200 to 600 Hz, bubbling fluidization occurs. Both the bed expansion and the bubble characteristics are strongly dependent on the sound frequency and sound pressure level. However, sound has almost no impact on the fluidization, when the sound frequency is extremely high, above 2000 Hz. A relatively high sound pressure level (such as 115 dB) is needed to initiate the fluidization. D

The fracture and acoustic properties of six commercial potato chips that differ in sensory hardness and sensory crispness were analysed and related in this work. Principal component analysis showed a correlation among the sensory attributes and the instrumental parameters (both mechanical and acoustic). Two components mainly explained the behaviour of the different potato chips. The first component was positively related to the number of force and sound events, to sound pressure level maximum, to the area under the force curve, and to sensory crispness, and negatively related to fat content; and the second component was positively related to the gradient (slope of the first part of the curve), the potato chip thickness, and to sensory hardness and sensory crispness. The behaviour of the different potato chips was explained by either one of the two components or by both components. Results indicate that certain degree of sensory hardness is necessary for higher crispness perception.

Calls at frequencies below the range of human hearing were recorded from two groups of captive Asian elephants (Elephas maximus). Most of the calls ranged in frequency from 14 to 24 Hz, with durations of 10-15 s (Fig. 1). With the nearest elephant 5 m from the microphone, sound pressure levels were 85 to 90 dB (re 20 ~tPa). These calls occurred in a variety of circumstances. Elephants are the first terrestrial mammals reported to produce infrasound. These calls may be important in the coordination of behavior in thick vegetation or among separated groups of elephants.

We review the mechanical origin of auditory-nerve excitation, focusing on comparisons of the magnitudes and phases of basilar-membrane (BM) vibrations and auditory-nerve fiber responses to tones at a basal site of the chinchilla cochlea with characteristic frequency approximately 9 kHz located 3.5 mm from the oval window. At this location, characteristic frequency thresholds of fibers with high spontaneous activity correspond to magnitudes of BM displacement or velocity in the order of 1 nm or 50 microm/s. Over a wide range of stimulus frequencies, neural thresholds are not determined solely by BM displacement but rather by a function of both displacement and velocity. Near-threshold, auditory-nerve responses to low-frequency tones are synchronous with peak BM velocity toward scala tympani but at 80-90 dB sound pressure level (in decibels relative to 20 microPascals) and at 100-110 dB sound pressure level responses undergo two large phase shifts approaching 180 degrees. These drasti...

We conducted 58 playback experiments with free-ranging African elephants in Etosha National Park, Namibia, to estimate the distance over which some of their low-frequency calls are audible to other elephants. We broadcast pre-recorded elephant calls to elephants that were 1.2 and 2.0 km from the speaker while making simultaneous video and audio recordings of their behavior. In order to reduce the risk of habituation, we used a variety of call types as stimuli. Elephants responded to playbacks at both 1.2 and 2.0 km, with a full response consisting of the elephant vocalizing, lifting and spreading its ears, remaining motionless in this position ('freezing'), moving the head from side to side ('scanning') and, in the case of males responding to female estrous calls, orienting to and finally walking 1 km or more towards the loudspeaker.

Vocal training (VT) has, in part, been associated with the distinctions in the physiological, acoustic, and perceptual parameters found in singers' voices versus the voices of nonsingers. This study provides information on the changes in the singing voice as a function of VT over time. Fourteen college voice majors (12 females and 2 males; age range, 17-20 years) were recorded while singing, once a semester, for four consecutive semesters. Acoustic measures included fundamental frequency (F 0 ) and sound pressure level (SPL) of the 10% and 90% levels of the maximum phonational frequency range (MPFR), vibrato pulses per second, vibrato amplitude variation, and the presence of the singer's formant. Results indicated that VT had a significant effect on the MPFR. F 0 and SPL of the 90% level of the MPFR and the 90-10% range increased significantly as VT progressed. However, no vibrato or singers' formant differences were detected as a function of training. This longitudinal study not only validates previous cross-sectional research, ie, that VT has a significant effect on the singing voice, but also it demonstrates that these effects can be acoustically detected by the fourth semester of college vocal training.

Aberrant, lesion-induced neuroplastic changes in the auditory pathway are believed to give rise to the phantom sound of tinnitus. Noise-induced cochlear damage can induce extensive fiber growth and synaptogenesis in the cochlear nucleus, but it is currently unclear if these changes are linked to tinnitus. To address this issue, we unilaterally exposed nine rats to narrowband noise centered at 12 kHz at 126 dB SPL for two hours and sacrificed them 10 weeks later for evaluation of synaptic plasticity (GAP-43 expression) in the cochlear nucleus. Noise-exposed rats along with three agematched controls were screened for tinnitus-like behavior with gap prepulse inhibition of the acoustic startle (GPIAS) before, 1-10 days after and 8-10 weeks after the noise exposure. All nine noise-exposed rats showed similar patterns of severe hair cell loss at high-and mid-frequency regions in the exposed ear. Eight of the 9 showed strong up-regulation of GAP-43 in auditory nerve fibers and pronounced shrinkage of the ventral cochlear nucleus (VCN) on the noiseexposed side, and strong up-regulation of GAP-43 in the medial ventral VCN, but not in the lateral VCN or the dorsal cochlear nucleus. GAP-43 up-regulation in VCN was significantly greater in Noise-No-Tinnitus rats than in Noise-Tinnitus rats. One Noise-No-Tinnitus rat showed no upregulation of GAP-43 in auditory nerve fibers and only little VCN shrinkage, suggesting that auditory nerve degeneration plays a role in tinnitus generation. Our results suggest that noiseinduced tinnitus is suppressed by strong up-regulation of GAP-43 in the medial VCN. GAP-43 upregulation most likely originates from medial olivocochlear neurons. Their increased excitatory input on inhibitory neurons in VCN may possibly reduce central hyperactivity and tinnitus.

In this study, we examine the use of capacitive micromachined ultrasonic transducers (CMUTs) with vacuum-sealed cavities for transmitting directional sound with parametric arrays. We used finite element modeling to design CMUTs with 40-μm-and 60-μm-thick membranes to have resonance frequencies of 46 kHz and 54 kHz, respectively. The wafer bonding approach used to fabricate the CMUTs provides good control over device properties and the capability to fabricate CMUTs with large diameter membranes and deep cavities. Each CMUT is 8 cm in diameter and consists of 284 circular membranes. Each membrane is 4 mm in diameter.

The startle response evoked by repeated presentation of a loud acoustic stimulus is regulated by the independent processes of sensitization and habituation. While schizophrenia is associated with information processing impairments, there is conflicting evidence regarding the existence of habituation deficits in schizophrenic patients. Recent clinical evidence, however, indicates that patients with schizophrenia display exaggerated startle sensitization and diminished habituation. Given the linkage between dopaminergic abnormalities and schizophrenia, the goal of the present investigation was to examine the effect of deleting D1 and D2-like dopamine receptors on sensitization and habituation of the acoustic startle reflex in mice. For these experiments, the acoustic startle reflex was assessed in dopamine D1, D2, and D3 receptor wild-type (WT) and knockout (KO) mice on a C57BL/6J background, using a methodology that can measure both sensitization and habituation. Mice lacking the D1 ...

Animal studies have led to the view that the acoustic medial olivocochlear (MOC) efferent reflex provides sharply tuned frequency-specific feedback that inhibits cochlear amplification. To determine if MOC activation is indeed narrow band, we measured the MOC effects in humans elicited by 60-dB sound pressure level (SPL) contralateral, ipsilateral, and bilateral noise bands as a function of noise bandwidth from 1/2 to 6.7 octaves. MOC effects were quantified by the change in stimulus frequency otoacoustic emissions from 40 dB SPL probe tones near 0.5, 1, and 4 kHz. In a second experiment, the noise bands were centered 2 octaves below probe frequencies near 1 and 4 kHz. In all cases, the MOC effects increased as elicitor bandwidth increased, with the effect saturating at about 4 octaves. Generally, the MOC effects increased as the probe frequency decreased, opposite expectations based on MOC innervation density in the cochlea. Bilateral-elicitor effects were always the largest. The ratio of ipsilateral/contralateral effects depended on elicitor bandwidth; the ratio was large for narrow-band probe-centered elicitors and approximately unity for wide-band elicitors. In another experiment, the MOC effects from increasing elicitor bandwidths were calculated from measurements of the MOC effects from adjacent half-octave noise bands. The predicted bandwidth function agreed well with the measured bandwidth function for contralateral elicitors, but overestimated it for ipsilateral and bilateral elicitors. Overall, the results indicate that (1) the MOC reflexes integrate excitation from almost the entire cochlear length, (2) as elicitor bandwidth is increased, the excitation from newly stimulated cochlear regions more than overcomes the reduced excitation at frequencies in the center of the elicitor band, and (3) contralateral, ipsilateral, and bilateral elicitors show MOC reflex spatial summation over most of the cochlea, but ipsilateral spatial summation is less additive than contralateral.

This paper presents the results of an evaluation of acoustic comfort of classrooms built according to a standard design. Three constructive designs located in the metropolitan area of Curitiba (Brazil) have been evaluated, two schools built under each of these three designs, in a total of six schools. The acoustic quality of the classrooms have been analyzed based on measurements

A portion of the lateral body wall overlying the lung cavity of the arboreal frog, Eleutherodactylus coqui, vibrates in response to free-field sound. Peak displacement amplitude of the body wall in response to a natural call note presented at 73 decibels sound pressure level is 1.70 x 10'9 m, roughly 8 decibels less than that of the ipsilateral eardrum, as measured by laser Doppler vibrometry. We show that the vibration magnitude varies predictably across the body profile and is posture and frequency dependent. Two routes to the inner ear are described for sounds impinging on the body wall; either of these accessory pathways could modify direct input from the peripheral auditory system and enhance sound localization in these small vertebrates.

Low-and high-frequency sounds were tested as a means of repelling blueback herring Alosa aestivalis in confined-area and open-water experiments. Confined-area tests were performed by analyzing the response of blueback herring in floating net-pens to sounds differing in frequency, sound pressure levels (SPLs, given in decibels [dB] in reference to 1.0 /*Pa), and pulse width. Highfrequency sounds between 110 and 140 kHz. at SPLs above 180 dB (at 1.0 m from the transducer) and at various pulse widths, elicited statistically significant (P < 0.05) avoidance responses by blueback herring. A reduced response was observed at sound frequencies of 100 and 150 kHz. Low-frequency sounds between 0.1 and 1 kHz at SPLs of 160-175 dB (at 1.0 m from the transducer) elicited only short-term startle responses. Field tests were performed at Richard B. Russell Dam (on the Savannah River at the Georgia-South Carolina border) to evaluate candidate transducers and amplifiers. In field evaluations a single high-frequency transducer emitting 124.6-and 130.9-kHz sounds at an SPL of 187 or 200 dB (at 1.0 m) partially repelled blueback herring that were approximately 60 m away from the transducer for periods of up to 1 h. These results suggest that high-frequency sound may provide an effective and inexpensive method, relative to structural measures, for reducing entrainment of blueback herring at hydropower stations.

Complementary low-dimensional techniques are modified to estimate the most energetic turbulent features of a Mach 0.85 axisymmetric jet in the flow&#39;s near-field regions via spectral linear stochastic estimation. This model estimate is three-dimensional, comprises all three components of the velocity field and is time resolved. The technique employs the pressure field as the unconditional input, measured within the hydrodynamic periphery of the jet flow where signatures (pressure) are known to comprise a reasonable footprint of the turbulent large-scale structure. Spectral estimation coefficients are derived from the joint second-order statistics between coefficients that are representative of the low-order pressure field (Fourier-azimuthal decomposition) and of the low-order velocity field (proper orthogonal decomposition). A bursting-like event is observed in the low-dimensional estimate and is similar to what was found in the low-speed jet studies of others. A number of low-di...

For signal detection and identification, the auditory system needs to integrate sound over time. It is frequently assumed that the quantity ultimately integrated is sound intensity and that the integrator is located centrally. However, we have recently shown that absolute thresholds are much better specified as the temporal integral of the pressure envelope than of intensity, and we proposed that the integrator resides in the auditory pathway's first synapse. We also suggested a physiologically plausible mechanism for its operation, which was ultimately derived from the specific rate of temporal integration, i.e., the decrease of threshold sound pressure levels with increasing duration. In listeners with sensorineural hearing losses, that rate seems reduced, but it is not fully understood why. Here we propose that in such listeners there may be an elevation in the baseline above which sound pressure is effective in driving the system, in addition to a reduction in sensitivity. We test this simple model using thresholds of cats to stimuli of differently shaped temporal envelopes and durations obtained before and after hearing loss. We show that thresholds, specified as the temporal integral of the effective pressure envelope, i.e., the envelope of the pressure exceeding the elevated baseline, behave almost exactly as the lower thresholds, specified as the temporal integral of the total pressure envelope before hearing loss. Thus, the mechanism of temporal integration is likely un-changed after hearing loss, but the effective portion of the stimulus is. Our model constitutes a successful alternative to the model currently favored to account for altered temporal integration in listeners with sensorineural hearing losses, viz., reduced peripheral compression. Our model does not seem to be at variance with physiological observations and it also qualitatively accounts for a number of phenomena observed in such listeners with suprathreshold stimuli.

The problem of mixed signals occurs in many different contexts; one of the most familiar being acoustics. The forward problem in acoustics consists of finding the sound pressure levels at various detectors resulting from sound signals emanating from the active acoustic sources. The inverse problem consists of using the sound recorded by the detectors to separate the signals and recover the original source waveforms. In general, the inverse problem is unsolvable without additional information. This general problem is called source separation, and several techniques have been developed that utilize maximum entropy, minimum mutual information, and maximum likelihood. In previous work, it has been demonstrated that these techniques can be recast in a Bayesian framework. This paper demonstrates the power of the Bayesian approach, which provides a natural means for incorporating prior information into a source model. An algorithm is developed that utilizes information regarding both the statistics of the amplitudes of the signals emitted by the sources and the relative locations of the detectors. Using this prior information, the algorithm finds the most probable source behavior and configuration. Thus, the inverse problem can be solved by simultaneously performing source separation and localization. It should be noted that this algorithm is not designed to account for delay times that are often important in acoustic source separation. However, a possible application of this algorithm is in the separation of electrophysiological signals obtained using electroencephalography (EEG) and magnetoencephalography (MEG).

Sound amplitude (measured as sound pressure level) is an acoustical parameter that has received little attention within communication research, especially in mammals. Although difficult to measure in the field, amplitude is a potentially important parameter of sexually selected signals. In North American plains bison, Bison bison, ‘bellows’ are low, guttural vocalizations made by bulls during the breeding season in the context of male–male contests. It has been hypothesized that bison use bellow amplitude to assess males during male–male competition or female mate choice. In this study, we tested the hypothesis that amplitude is significantly related to measures of bull competitive ability (quality, condition and motivation), and thus, could function as a sexually selected signal. During peak rut over 2 years, courtship and threat behaviours were recorded daily. During observation sessions, bellow amplitude was measured as peak sound pressure levels using a sound level meter. Subsequent genetic parentage analysis determined offspring sired by males. Based on aspects of signalling and game theory, we predicted positive associations between amplitude and mating and reproductive success, dominance, physical condition, motivation to retain females, age and weight. Our results supported a positive association between amplitude and both physical condition and motivation. Conversely, the results showed a negative association between amplitude and quality, as measured by mating and reproductive success. Supporting evidence and alternative hypotheses for these results are explored. Our findings provide support for the notion that bellow amplitude could be used as a sexually selected signal to assess rival males during male–male competition.

The aim of this study was to investigate the physical variations related to stress and the vocal expression of emotional state . One male and two female subjects produced the nonsense utterance ''paappa paap pa paappa'' simulating five emotional states : neutral , surprise , sadness , enthusiasm , and anger . The main stress was on the italicized syllable . Fundamental frequency (f 0 ) , sound pressure level (SPL) , and intraoral pressure were measured . Glottal flow was estimated from the acoustic signal by means of an inverse filtering method (IAIF) .

Patients with steeply sloping hearing losses of cochlear origin may exhibit enhanced difference limens for frequency (DLFs) near the cut-off frequency (Fc) of their hearing loss. This effect has been related to observations in deafened animals of an over-representation of Fc in the primary auditory cortex. However, alternative interpretations in terms of peripheral mechanisms have not been eliminated. In the present study, we assessed the possible role of two peripheral mechanisms [loudness cues and spontaneous otoacoustic emissions (SOAEs)] in a group of patients with high-frequency hearing loss. We tested ®rst whether the DLF enhancement effect was still observed under conditions where subjects could not rely on loudness cues to perform the frequency discrimination task. To achieve this, we adjusted the nominal level of each stimulus so that it fell on an equal loudness contour measured at very ®ne (1/8 octave) frequency intervals, and we roved the level of each stimulus over a large range (12 dB). Under these conditions, the DLF enhancement was still observed in all patients; this demonstrates that the effect cannot be explained simply by loudness cues. We then screened the patients for SOAEs to test whether the DLF enhancement effect could be explained by the presence of such emissions in the vicinity of the Fc. None of the patients exhibited SOAEs. Finally, we tested whether the patients had cochlear dead regions, i.e. regions lacking functional inner hair cells and/or auditory nerve ®bres. Using a re®ned version of a noninvasive clinical test for the identi®cation of dead regions, we assessed the presence of such regions in ®ne frequency steps (1/4 octave) up to very high frequencies. All of the patients had cochlear dead regions. The ®rst two ®ndings support the hypothesis that DLF enhancement is due to injury-induced central reorganization in the auditory system. The last one is consistent with neurophysiological data in animals, which suggest that complete deprivation from auditory input at certain cochlear sites may be a necessary condition for the occurrence of injury-induced cortical reorganization.

AbstractöAcoustic trauma is the major cause of hearing loss in industrialised nations. We show in guinea-pigs that sound exposure (6 kHz, 120 dB sound pressure level for 30 min) leads to sensory cell death and subsequent permanent hearing loss. Ultrastructural analysis reveals that degeneration of the noise-damaged hair cells involved di¡erent mechanisms, including typical apoptosis, autolysis and, to a lesser extent, necrosis. Whatever the mechanisms, a common feature of noise damage to hair cells was mitochondrial alteration. Riluzole (2-amino-6-tri£uoromethoxy benzothiazole) is a neuroprotective agent that prevents apoptosis-and necrosis-induced cell death. Perfusion of riluzole into the cochlea via an osmotic minipump prevents mitochondrial damage and subsequent translocation of cytochrome c, DNA fragmentation, and hair cell degeneration. This was con¢rmed by functional tests showing a clear dose-dependent reduction (ED 50 = 16.8 WM) of permanent hearing loss and complete protection at 100 WM. Although less e⁄cient than intracochlear perfusion, intraperitoneal injection of riluzole rescues the cochlea within a therapeutic window of 24 h after acoustic trauma.

Optical stimulation of neural tissue within the cochlea was described as a possible alternative to electrical stimulation. Most optical stimulation was performed with pulsed lasers operating with near-infrared (NIR) light and in thermal confinement. Under these conditions, the coexistence of laser-induced optoacoustic stimulation of the cochlea (“optophony”) has not been analyzed yet. This study demonstrates that pulsed 1850-nm laser light used for neural stimulation also results in sound pressure levels up to 62 dB peak-to-peak equivalent sound pressure level (SPL) in air. The sound field was confined to a small volume along the laser beam. In dry nitrogen, laser-induced acoustic events disappeared. Hydrophone measurements demonstrated pressure waves for laser fibers immersed in water. In hearing rats, laser-evoked signals were recorded from the cochlea without targeting neural tissue. The signals showed a two-domain response differing in amplitude and latency functions, as well as sensitivity to white-noise masking. The first component had characteristics of a cochlear microphonic potential, and the second component was characteristic for a compound action potential. The present data demonstrate that laser-evoked acoustic events can stimulate a hearing cochlea. Whenever optical stimulation is used, care must be taken to distinguish between such “optophony” and the true optoneural response.

Weekly sound surveys ͑n =63͒ were collected, using 5 s sampling intervals, for two modern neonatal intensive care units ͑NICUs͒. Median weekly equivalent sound pressure levels ͑L EQ ͒ for NICU A ranged from 61 to 63 dB ͑A weighted͒, depending on the level of care. NICU B L EQ measurements ranged from 55 to 60 dB ͑A weighted͒. NICU B was recently built with a focus on sound abatement, explaining much of the difference between the two NICUs. Sound levels exceeded 45 dB ͑A weighted͒, recommended by the American Academy of Pediatrics, more than 70% of the time for all levels of care. Hourly L EQ s below 50 dB ͑A weighted͒ and hourly L 10 s below 55 dB ͑A weighted͒, recommended by the Sound Study Group ͑SSG͒ of the National Resource Center, were also exceeded in more than 70% of recorded samples. A third SSG recommendation, that the 1 s L MAX , should not exceed 70 dB ͑A weighted͒, was exceeded relatively infrequently ͑Ͻ11% of the time͒. Peak impulse measurements exceeded 90 dB for 6.3% of 5 s samples recorded from NICU A and 2.8% of NICU B samples. Twenty-four h periodicities in sound levels as a function of regular staff activities were apparent, but short term variability was considerable.

The human hearing range is from 20 Hz to 20 kHz. However, many animals can hear much higher sound frequencies. Dolphins, especially, have a hearing range up to 300 kHz. To our knowledge, there is no data of a reported wide-band sound frequency earphone to satisfy both humans and animals. Here, we show that graphene earphones, packaged into commercial earphone casings can play sounds ranging from 100 Hz to 50 kHz. By using a one-step laser scribing technology, wafer-scale flexible graphene earphones can be obtained in 25 min. Compared with a normal commercial earphone, the graphene earphone has a wider frequency response (100 Hz to 50 kHz) and a three times lower fluctuation (±10 dB). A nonlinear effect exists in the graphene-generated sound frequency spectrum. This effect could be explained by the DC bias added to the input sine waves which may induce higher harmonics. Our numerical calculations show that the sound frequency emitted by graphene could reach up to 1 MHz. In addition, we have demonstrated that a dog wearing a graphene earphone could also be trained and controlled by 35 kHz sound waves. Our results show that graphene could be widely used to produce earphones for both humans and animals.

Voluntary restriction of body movement is associated with the reduction of sound pressure level (SPL) peaks in western contemporary popular singing. This paper investigated whether overall SPL and SPL range are affected when singers voluntarily restrain their movement during performance. Six professional singers performed a section of a song in two performance modes: first with no constraints placed on their body behaviour and again when directed to stand still. Overall SPL and SPL range were compared for the two conditions. The calculation of percentiles revealed reductions in SPL in the no movement condition across all SPL levels for all singers. With respect to absolute range, contrary to expectation, the SPL minima were reduced by a degree equivalent to the reduction in SPL maxima in the majority of singers. To our knowledge, this phenomenon has not been noted previously, possibly because this compensatory effect disguises the overall reduction in SPL. This effect may be automatic and beyond the conscious control of singers. It remains to be studied whether this effect exists in other styles of singing and what aspect of movement restraint triggers this effect. Verbal directions curbing body movement may have detrimental effects on acoustic output even in experienced singers.

Subjects adjusted the sound pressure level of a l,OOO-Hz tone or the luminance of a 10°target on a translucent screen to match their anticipated subjective tension in performing before audiences represented by 1-16 color slides of old or young males or females. Consistent with a new theory of social impact, "tension" was a multiplicative power function of the number (exponent~.6) of people in the audience and their ages, with older (37-year-old) audiences generating 2~3 times the tension of younger (teen-age) audiences. Male audiences elicited 5%-40% more tension than females. Social impact, broadly defined as any effect of the presence or actions of other people on an individual, can be analyzed as the result of social forces operating in a social force field in much the same way that physical forces operate in physical force fields (Dodd, 1950; Lewin,)°15; Stewart, 1952; Zipf, 1949; Knowles, Note 1). Given this conception, we should expect that the intensity of a social flux should be determined by factors and laws similar to those that determine, for example, the intensity of a luminous flux. Just as the amount of light falling on a surface is determined by the wattage, proximity, and number of bulbs shining on that surface, so too the effect of other people in a social situation is determined by the importance, closeness, and number of people in that situation. When a person is the target of social forces emanating from other people, then, a new theory of social impact (Latane, Note 2) suggests that the magnitude of those forces should be a multiplicative function of the strength, immediacy, and number of people present. As in the case of physical stimuli, however, the psychological effect of other people may not be simply a linear function of their number or strength. Rather, social impact may obey psychosocial laws similar to the psychophysical laws which govern the subjective impact of such physical dimensions as sound or light intensity. With respect to increases in the number of people affecting an individual, for This research was supported by National Science Foundation Grant GS40194 and by a fellowship from the John Simon Guggenheim Foundation to Bibb Latane, Lewis Hinkle built the apparatus, Stanley w. Smith calibrated it, James M. Lynn provided the audiometer for loudness matching, and Marcus R. Walker made and provided the sets of slides. We thank

Insects have evolved a marked diversity of mechanisms to produce loud conspicuous sounds for efficient communication. However, the risk of eavesdropping by competitors and predators is high. Here, we describe a mechanism for producing extremely lowintensity ultrasonic songs (46 dB sound pressure level at 1 cm) adapted for private sexual communication in the Asian corn borer moth, Ostrinia furnacalis. During courtship, the male rubs specialized scales on the wing against those on the thorax to produce the songs, with the wing membrane underlying the scales possibly acting as a sound resonator. The male's song suppresses the escape behavior of the female, thereby increasing his mating success. Our discovery of extremely low-intensity ultrasonic communication may point to a whole undiscovered world of private communication, using ''quiet'' ultrasound.

Males of the bushcricket Mecopoda elongata synchronise or alternate their chirps with their neighbours in an aggregation. Since synchrony is imperfect, leader and follower chirps are established in song interactions; females prefer leader chirps in phonotactic trials. Using playback experiments and simulations of song oscillator interactions, we investigate the mechanisms that result in synchrony and alternation, and the probability for the leader role in synchrony. A major predictor for the leader role of a male is its intrinsic chirp period, which varies in a population from 1.6 to 2.3 s. Faster singing males establish the leader role more often than males with longer chirp periods. The phase-response curve (PRC) of the song oscillators differs to other rhythmically calling or flashing insects, in that only the disturbed cycle is influenced in duration by a stimulus. This results in sustained leader or follower chirps of one male, when the intrinsic chirp periods of two males differ by 150 ms or more. By contrast, the individual shape of the male’s PRC has only little influence on the outcome of chirp interactions. The consequences of these findings for the evolution of synchrony in this species are discussed.

Apoptosis is responsible for cochlear cell death induced by noise. Here, we show that transgenic (TG) mice that overexpress X-linked inhibitor of apoptosis protein (XIAP) under control of the ubiquitin promoter display reduced hearing loss and cochlear damage induced by acoustic overstimulation (125 dB sound pressure level, 6 h) compared with wild-type (WT) littermates. Hearing status was evaluated using the auditory brainstem response (ABR), whereas cochlear damage was assessed by counts of surviving hair cells (HCs) and spiral ganglion neurons (SGNs) as well as their fibers to HCs. Significantly smaller threshold shifts were found for TG mice than WT littermates. Correspondingly, the TG mice also showed a reduced loss of HCs, SGNs and their fibers to HCs. HC loss was limited to the basal end of the cochlea that detects high frequency sound. In contrast, the ABRs demonstrated a loss of hearing sensitivity across the entire frequency range tested (2-32 kHz) indicating that the hearing loss could not be fully attributed to HC loss alone. The TG mice displayed superior hearing sensitivity over this whole range, suggesting that XIAP overexpression reduces noise-induced hearing loss not only by protecting HCs but also other components of the cochlea. Gene Therapy advance online publication, 13 January 2011;

We have recently discovered a paradoxical aftereffect associated with inhibition in the gerbil auditory midbrain. Single neurons in the inferior colliculus (IC) were assessed for sensitivity to a virtual motion stimulus produced by modulating the interaural level difference (ILD), a major cue for sound localization. The class of neuron studied was predominantly excited by contralateral stimulation and inhibited by ipsilateral stimulation. Sound pressure level was modulated trapezoidally at the ipsilateral &quot;inhibitory&quot; ear, whereas the contralateral &quot;excitatory&quot; level remained constant. When the inhibitory stimulus was decreased within a range of sound levels that maintained suppression under static conditions, an unexpected discharge was often elicited, apparently because of an aftereffect of synaptic inhibition. In contrast, when the inhibitory stimulus was increased within a range of sound levels that produced only modest suppression under static conditions, ne...

Noise pollution is an interfering air-pollutant which possesses both auridtory and a host of nan-aduitory effects on the exposed population. Since there is no medicine to cure hearing loss prevention to overt exposure is the only alternative left. The study reports community noise levels measured during day time in a fast developing semi-urban area of Nepal. The noise levels were mesured following standard procedure using calibrated sound pressure level meter at many places predominated by both commerical and residential tenaments at Banepa town particularly reflecting motor vehicular traffic prone areas. A small exercise of nose generated by different vehicles that frequent on the arterial roads has also been carried out. To delineate the perception about the noise and its significance on health of community a representive sample of public has been interviewed using a questionnaire. The results indicate high noise levels, surpassing on many occasions to the prescribed levels. Overall minimum and maximum noise levels for the Main Road are 60.1dB (A) and 110.2 dB (A). Bus parks and Bus stops had minimum and maximum noise levels were 63.9 dB (A) and 110.2dB (A). The picture near residential tenaments also had subtantial levels of noise, a minimum of 59.11dB (A). The noise levels produced by different motor vehicles ranged from 121 to 91.2 dB(A), which was substantial. The study observes motor vehicles as main source in the town. The perception survey indicate high prevalence of head aches, lack of concentration, sleep. Since levels lie much above the prescribed limts there is am imminent health risk to the exposed population and the study suggests control measures to be instituted on a priority.

Vocal warm-up was studied in terms of changes in voice parameters during a 45-minute vocal loading session in the morning. The voices of a randomly chosen group of 40 female and 40 male young students were loaded by having them read a novel aloud. The exposure groups (5 females and 5 males per cell) consisted of eight combinations of the following factors: (1) low (25 ± 5%) or high (65 ± 5%) relative humidity of ambient air; (2) low [< 65 dB(SPL)] or high [> 65 dB(SPL)] speech output level during vocal loading; (3) sitting or standing posture during vocal loading. Two sets of voice samples were recorded: a resting sample before the loading session and a loading sample after the loading session. The material recorded consisted of /pa:ppa/ words produced normally, as softly and as loudly as possible in this order by all subjects. The long /a/ vowel of the test word was inverse-filtered to obtain the glottal flow waveform. Time domain parameters of the glottal flow [open quotient (OQ), closing quotient (CQ), speed quotient (SQ), fundamental frequency (F 0)], amplitude domain parameters of the glottal flow [glottal flow (f AC) and its logarithm, minimum of the first derivative of the glottal flow (d peak) and its logarithm, amplitude quotient (AQ), and a new parameter, CQAQ], intraoral pressure (p), and sound pressure level (SPL) values of the phonations were analyzed. Voice range profiles (VRP) and the singer's formant (g/G, a/A, c1/c, e1/e, g1/g for females/males) of the loud phonation were also measured. Statistically significant differences between the preloading and postloading samples could be seen in many parameters, but the differences depended on gender and the type of phonation. In females the values of CQ, AQ, and CQAQ decreased and the values of SQ and p increased in normal phonations; the values of f AC , d peak , and SPL increased in soft phonations; the values of AQ and CQAQ decreased in loud phonations; the harmonic energy in the singer's formant region increased significantly at every pitch. In males the values of OQ and AQ de-VRP, whereas the case was the opposite for standing position.