Occupational Noise Exposure Standards and Regulations

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1. Noise

Article 70. In occupational exposure to noise, a distinction is made between stable noise, fluctuating noise, and impulse noise.

Article 71. Steady noise is noise that has fluctuations in instantaneous sound pressure level less than or equal to 5 dB (A) slow, during an observation period of 1 minute.

Fluctuating noise is noise that presents fluctuations in instantaneous sound pressure level in excess of 5 dB (A) slow during an observation period of 1 minute.

Impulsive noise is noise that has acoustic energy impulses for less than 1 second at intervals of more than 1 second.

Article 72. Measurements of steady noise, fluctuating noise, and impulse noise must be made with an integrating sound level meter or a dosimeter meeting the requirements outlined for types 0, 1, or 2, set in the standards: IEC 651-1979, IEC 804-1985, and ANSI S. 1.4-1983.

2. Noise Exposure Limits

Article 73. In noise exposure, whether stable or fluctuating, the equivalent continuous sound pressure level (Leq or NPSeq) should be measured. This is expressed in decibels weighted 'A' with a slow response, i.e., in dB (A) slow.

Article 74. Occupational exposure to steady or fluctuating noise must be controlled so that for an 8-hour workday, no worker may be exposed to an equivalent continuous sound pressure level above 85 dB (A) slow, measured at the employee's ear position.

Article 75. Levels of equivalent continuous sound pressure, different from 85 dB (A) slow, are permitted provided that the time of worker exposure to noise does not exceed the values shown in the following table:

When daily exposure to noise is composed of two or more periods of exposure to different equivalent continuous noise pressure levels, the combined effect of those periods that are equal to or above 80 dB (A) slow should be considered. In this case, the Daily Noise Dose (D) should be calculated using the following formula:

D = (Te1/Tp1) + (Te2/Tp2) + ... + (Ten/Tpn)

  • Te = Total time of exposure to a particular NPSeq
  • Tp = Total time of exposure permitted at that NPSeq

The maximum daily noise dose allowable is 1 (100%).

Article 77. Under no circumstances will workers lacking personal hearing protection be allowed to be exposed to equivalent continuous sound pressure levels above 115 dB (A) slow, regardless of the type of work.

1.2 Impulsive Noise

Article 78. Impulsive noise exposure must be measured in peak sound pressure level (SPL peak), expressed in decibels weighted "C", i.e., dB (C) Peak.

Article 79. Occupational exposure to impulse noise should be controlled so that for an 8-hour day, no worker may be exposed to a peak sound pressure level above 95 dB (C) Peak, measured at the worker's ear position.

Article 80. Peak sound pressure levels different from 95 dB (C) Peak are permitted, provided that the length of exposure to noise for the worker does not exceed the values shown in the following table:

Article 81. Under no circumstances will workers lacking personal hearing protection be allowed to be exposed to peak noise pressure levels exceeding 140 dB (C) peak, regardless of the type of work.

Article 82. When a worker is using personal hearing protection, they shall be deemed to comply with the provisions of Articles 75 and 80 of this regulation if the effective sound pressure level does not exceed the maximum permissible limits laid down in the tables mentioned in those articles.

For the purposes of this regulation, the effective sound pressure level shall mean the difference between the equivalent continuous sound pressure level or peak sound pressure level, depending on whether the noise is stable, fluctuating, or impulsive respectively, and the noise reduction granted by the hearing protector. In both cases, the noise reduction will be calculated in accordance with official standards in force concerning hearing protection.

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