Juan Antonio Ortiz Garcia
Ingenieria Acust. Spectrum, S. A. de C. V. Apaseo el Allto No. 21-2, Colonia San Bartolo Atepehuacan, Delegacion Gustavo A. Madero, Mexico 07730 D.F., Mexico
Since 1985, labor regulations on noise exposure have existed, and as in other countries, the quantity employed is the A-weighted sound-pressure level. Maximum allowable exposure levels were taken from ISO-1999-1975. According to local statistics of professional illness, hearing loss occupies second place in importance. The measurement results ofA-weighted sound-pressure levels in different types of Mexican industries, from 1990 to 1993, are described. These measurements were made in concordance with official methodology. The results showed that less than 50% of a sampled populations stayed in a noisy ambient (continuous or fluctuating) with levels higher than 90 dBA. It is considered that A weighted sound-pressure level is not enough to properly describe noise at the workplace; due to high level values usually encountered at low frequencies, which, even though they are not normally audible, may cause workers' low performance, beside other biological and psychological effects. Frequency analysis results of the same industries and how they are employed for the calculation of other quantities, like loudness and noisiness, are also described.