Felipe Vergara

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2 Sound Pressure Levels in Protected Ear ( When Hearing Protector is Worn ) 2 . 2 . 1 Long Method

The noise exposure at an ear protected with the use of a hearing protector can be calculated usin... more The noise exposure at an ear protected with the use of a hearing protector can be calculated using the long method, in which the attenuation for each octave frequency band is calculated, or a simple method which involves subtracting a single-number noise reduction rating from the overall noise exposure level. In this paper, a comparison of these two methods is carried out using the 100 industrial noise spectra of NIOSH, with higher levels in either the low, middle or high frequency bands. The methods used to determine the noise exposure level of the protected ear (when the hearing protector is worn) are based on the long method (NIOSH method #1) and the simple method. Three types of hearing protector devices (HPDs) were tested: earmuff, earmuff attached to hard hat and earplug. The characteristics of each method were analyzed and the noise exposure levels calculated for the different types of industrial noise spectra were compared.

Evaluation of earmuff attenuation by finite element method when subject to high-intensity impulsive noise

Numerical and Experimental Study of Impulsive Sound Attenuation of an Earmuff

Shock and Vibration, 2002

This work compares the results of laboratory experiments with numerical modelling using the finit... more This work compares the results of laboratory experiments with numerical modelling using the finite element method in order to assess the attenuation of hearing protectors under conditions of high amplitude impulse noise. Comparative data for the finite element simulation was provided from a series of experiments using a shock tube, acoustic test fixture, ear canal simulator and partial head form. The numerical model comprised a finite element mesh of fluid and porous materials in order to model the earmuff hearing protector coupled to the auditory canal. The results show that a simple 2-D finite element model is capable of making a reasonable prediction of the attenuation of an earmuff provided that headband force is also included in the model.

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Noise Pollution in Hospitals and its Impacts on the Health Care Community and Patients

The Journal of the Acoustical Society of America

Noise pollution in hospitals is known to affect the health of patients, but it also impacts the s... more Noise pollution in hospitals is known to affect the health of patients, but it also impacts the staff. Most of a hospital’s environment is affected by the sounds of equipment and machines with high sound pressure levels (SPL). We directed the study of both quantitative aspects to reduce SPL and qualitative research which considers the soundscapes of hospitals and people's perceptions. The main goal of this study was to do an assessment of the noise pollution in hospitals in Brazil and USA to investigate the effects on the health care community and patients. The objectives were: 1) Implement a sound mapping, day and night, in different units of the hospital; 2) Characterize the variations of the SPL of the various noise sources in the hospital's care units; 3) Develop and apply a qualitative assessment based on the opinion of users of the hospital in relation to the noise perceived by them; 4) Establish/propose an analytical-experimental model based on correlations of objecti...

Experimental observation of non-linear effects in the propagation of a Friedlander pulse in a finite-length closed tube

Journal of Sound and Vibration, 2004

Avaliação da exposição de ope ra dores de teleatendimento a ruído Telemarketing operators' noise exposure assessment

Existe um crescimento elevado da oferta de produtos e serviços das empresas de teleatendimento. P... more Existe um crescimento elevado da oferta de produtos e serviços das empresas de teleatendimento. Porém, os operadores usuários de fones de ouvido mostram-se afetados pela exposição a ruído, podendo estar sujeitos à perda auditiva permanente e irreversível devido à exposição acima dos limites permissíveis. Os métodos tradicionais de medição da exposição a ruído não são adequados quando a fonte sonora é instalada diretamente sobre o sistema auditivo externo (orelha) através do uso de fones. Neste trabalho, a norma ISO 11904 é usada para avaliar a exposição a ruído em operadores de teleatendimento, considerando duas técnicas: cabeça artificial padronizada e microfone em ouvido real. Os resultados obtidos demonstraram que os dois métodos aplicados são eficientes e efetivos, podendo contribuir na avaliação apropriada da exposição a ruído em usuários de fones de ouvido de teleatendimento.

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Objective measurements for the assessment of hearing protectors attenuation at high level impulsive noise

Journal of The Acoustical Society of America, 2002

The evaluation of hearing protectors for the attenuation of high amplitude impulsive noise cannot... more The evaluation of hearing protectors for the attenuation of high amplitude impulsive noise cannot be carried out using the conventional subjective Real Ear Attenuation at Threshold (REAT) technique. In the case for high level impulsive noise it is not possible to conduct subjective type tests with volunteer listeners, therefore, other methods based on using artificial human head forms need to be considered. In this paper we present an objective technique that uses an artificial head, ear-canal simulator and shock tube to assess earplug and earmuff protectors. The shock tube is used as a means of producing controlled repeatable high amplitude pressure pulses (>140 dB) of varying rise time, amplitude, and duration. The artificial head and ear simulator with a protector are mounted inside the shock tube and subjected to a high level sound pulse. Pressure levels are measured simultaneously outside of the protector (incident pulse) and inside at the ear simulator at the eardrum position. The attenuation of peak pressure levels in the time domain and the corresponding spectra of the pulses are determined. The technique offers pointers towards future standards of performance hearing protectors for applications with high level impulsive noise.

Barbosa A R

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