SATURATION AND MASKING IN AUDITORY REPRESENTATION. pptx

Journal of the Optical Society of America, 1981

The level of reflectance of pigmented surfaces observed in daylight affects saturation growth in different ways, depending on the wavelength of the samples. Numerical and matching judgments collected in previous experiments were replotted in families of monochromatic (constant hue) saturation power functions for blue, green, yellow, and red. For each hue the set of functions intersected at a point at which the calorimetric purity and saturation were invariant with reflectance. The points of intersection were: blues, 0.081 colorimetric purity (Pc) and 2.7 cromes; greens, 0.257 Pc and 4.6 cromes; yellows, 0.694 Pc and 8.3 cromes; and reds, 0.144 P, and 3.6 cromes. A straight line fitted to these four intersecting points makes it possible to interpolate other intersecting points for other hues.

The Journal of the Acoustical Society of America, 1966

A masking stimulus, either visual or auditory, raises the exponent of the psychophysical function relating sensation to stimulus. This power transformation applies only to the part of the function that is influenced by the masking stimulus. Since a given masking noise affects only weaker stimuli, the result is a discontinuous loudness function, which resembles the discontinuous brightness function produced by a glare. The loudness functions for low-frequency stimuli resemble those obtained under masking, as do also the recruitment functions in hard-of-hearing ears. The matching of the apparent brightness of a visual target to a masking surround can be done with relatively high precision, as in standard photometry. In an analogous fashion, the loudness of a pure tone immersed in a white masking noise can be matched to the loudness of the noise. As with visual stimuli, the mutual inhibition between tone and noise improves the precision of the loudness matching, though it still remains...

Journal of the Optical Society of America, 1963

Scales relating saturation to clorimetric purity have been derived from magnitude estimations for red (W29) and green (W65) test stimuli of 4° and 1.50 subtense. Scales based on homochromatic comparisons at several luminance levels follow a power-law form, with exponents ranging from 1.80 to 2.30. There is evidence that saturation scales for red and green light differ in slope, with the red scale being of consistently higher slope than the green. This difference is demonstrated clearly by heterochromatic saturation matches for a large number of clorimetric purities, but is not substantiated by magnitude estimations utilizing heterochromatic comparisons. It is suggested that observers are not able to apply a ratio definition of saturation in making quantitative comparisons of heterochromatic stimuli by the method of magnitude estimation, and that real differences between saturation scales for differing hues may be masked by the adoption of median magnitude estimations as a quantitative index of perceived saturations.

Journal of the Acoustical Society of America, 1979

Behavioural Brain Research, 1990

Single auditory cortical neurons express their sensitivity to the amplitude of a preferred-frequency tone pulse as either a monotonic, saturating intensity profile or as a non-monotonic, bell-shaped intensity function. In the presence of continuous, wideband noise masking, the tone intensity profile is displaced toward higher tone levels. The magnitude of the tone threshold adjustments brought about by increments in noise level very closely match the elevations in noise amplitude. The mechanisms underlying the threshold adjustments likely include neural adaptation. This is because the tone threshold shifts seen in the spike count data are paralleled by spike latency data, and because recovery of tonal sensitivity following noise offset proceeds in a negatively-accelerating fashion. In some instances, the slope of the masked tone intensity profile is greater than that for unmasked tones. For masked tone levels evoking submaximal responses, this has the consequence that cortical responses to masked tones are somewhat more salient than those for unmasked tones of comparable suprathresbold level. These observations bolster our understanding of the psychophysics of noise-masking in normal listeners, and they provide a partial explanation of the difficulty shown by patients with temporal lobe lesions in discriminating signals in noise.

The Journal of the Acoustical Society of America, 2003

The influence of the degree of envelope modulation and periodicity on the loudness and effectiveness of sounds as forward maskers was investigated. In the first experiment, listeners matched the loudness of complex tones and noise. The tones had a fundamental frequency ͑F0͒ of 62.5 or 250 Hz and were filtered into a frequency range from the 10th harmonic to 5000 Hz. The Gaussian noise was filtered in the same way. The components of the complex tones were added either in cosine phase ͑CPH͒, giving a large crest factor, or in random phase ͑RPH͒, giving a smaller crest factor. For each F0, subjects matched the loudness between all possible stimulus pairs. Six different levels of the fixed stimulus were used, ranging from about 30 dB SPL to about 80 dB SPL in 10-dB steps. Results showed that, at a given overall level, the CPH and the RPH tones were louder than the noise, and that the CPH tone was louder than the RPH tone. The difference in loudness was larger at medium than at low levels and was only slightly reduced by the addition of a noise intended to mask combination tones. The differences in loudness were slightly smaller for the higher than for the lower F0. In the second experiment, the stimuli with the lower F0s were used as forward maskers of a 20-ms sinusoid, presented at various frequencies within the spectral range of the maskers. Results showed that the CPH tone was the least effective forward masker, even though it was the loudest. The differences in effectiveness as forward maskers depended on masker level and signal frequency; in order to produce equal masking, the level of the CPH tone had to be up to 35 dB above that of the RPH tone and the noise. The implications of these results for models of loudness are discussed and a model is presented based on neural activity patterns in the auditory nerve; this predicts the general pattern of loudness matches. It is suggested that the effects observed in the experiments may have been influenced by two factors: cochlear compression and suppression.

The Journal of the Acoustical Society of America, 1974

Acoustical Physics, 2011

A psychoacoustic method for measuring masking thresholds based on the application of single type stimuli and maskers intended for revealing compressive nonlinearity of displacements of the cochlea basila membrane and evaluation of the frequency resolution of hearing in a narrow frequency range near the central frequency of the stimulus is considered. High frequency pulses with an envelope in the form of a Gaussian function with a sinusoidal filling with the frequency band corresponding to the width of the critical hearing band have been used as stimuli (referred to as compact). Noises with a spike structure of the ampli tude spectrum with a limited frequency band width served as maskers. With the central frequencies of stimuli and maskers being equal, a band noise with the central frequency corresponding with a spike of an indented spectrum was called an on (rip) frequency masker, while that with the central frequency corresponding to a dip in an indented spectrum was called an off(rip) frequency masker. The central frequencies and frequency bands of the stimuli and maskers were 4 kHz and 1000 Hz, respectively. The spike (dip) frequencies of an indented amplitude spectrum of a masker were 1000 Hz. In the case of successive and simultaneous masking, the dependences of the thresholds of off (rip) frequency masking of compact stimuli on the masker level revealed compressive nonlinearity of basila membrane displacements. However, threshold on (rip) /off (rip) fre quency masking differences visualized it much better. The estimates of the frequency resolution obtained under conditions of simultaneous masking of compact stimuli during variations in the frequency of spikes of indented masker spectra of low and medium levels corresponded to the width of the critical hearing band measured using a classical method of tone masking by a pair of narrow band noise maskers. Within the spike frequency range of 500-2000 Hz, the steepness of the dependence of off (rip) masking of compact stimuli on the spike frequency decreased with an increase in masker levels that pointed to a possible effect of compressive properties of basila membrane displacements on this parameter.

The Journal of the Acoustical Society of America, 2002

Thresholds for the detection of harmonic complex tones in noise were measured as a function of masker level. The rms level of the masker ranged from 40 to 70 dB SPL in 10-dB steps. The tones had a fundamental frequency ͑F0͒ of 62.5 or 250 Hz, and components were added in either cosine or random phase. The complex tones and the noise were bandpass filtered into the same frequency region, from the tenth harmonic up to 5 kHz. In a different condition, the roles of masker and signal were reversed, keeping all other parameters the same; subjects had to detect the noise in the presence of a harmonic tone masker. In both conditions, the masker was either gated synchronously with the 700-ms signal, or it started 400 ms before and stopped 200 ms after the signal. The results showed a large asymmetry in the effectiveness of masking between the tones and noise. Even though signal and masker had the same bandwidth, the noise was a more effective masker than the complex tone. The degree of asymmetry depended on F0, component phase, and the level of the masker. The maximum difference between masked thresholds for tone and noise was about 28 dB; this occurred when the F0 was 62.5 Hz, the components were in cosine phase, and the masker level was 70 dB SPL. In most conditions, the growth-of-masking functions had slopes close to 1 ͑on a dB versus dB scale͒. However, for the cosine-phase tone masker with an F0 of 62.5 Hz, a 10-dB increase in masker level led to an increase in masked threshold of the noise of only 3.7 dB, on average. We suggest that the results for this condition are strongly affected by the active mechanism in the cochlea.