Measurement of noise exposure
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This is the fifth edition of CSA Z107.56, Measurement of noise exposure. This edition supersedes the previous editions published in 2013, 2006, 1994, and 1986.
Key changes to this edition include the following:
a) instrument selection and requirements for noise-measuring equipment including removal of non- integrating sound level meters for measuring noise exposure have been updated;
b) the microphone in a real ear (MIRE) method has been extended to hearing protectors with built-in noise monitoring capabilities;
c) the artificial ear method (admissible types and procedures) for sources close to the ear has been updated;
d) the calculation procedure (A-weighted effective speech level for one-sided and two-sided headsets) of the estimation method for sources close to the ear has been updated;
e) Annex B has been updated to provide clarity on the use of an energy average instead of an arithmetic average when studying distributions of measured noise levels. Addition of new Tables B.1 and B.2 to align with current methods of calculating uncertainty of noise exposure harmonizes the approach with ISO 9612;
f) a new informative annex (Annex D) on walk-through surveys and noise level surveys has been included;
g) the procedure for the use of LOSHA has been removed and is no longer recommended
h) the definitions have been updated; and
i) the reference publications (Clause 2) have been updated.
This Standard should be used in conjunction with CSA Z1007, Hearing loss prevention program (HLPP) management, which deals with all aspects of the creation and management of hearing conservation programs. This Standard complements other CSA hearing conservation standards, including CSA Z94.2 (hearing protection), CSA Z107.6 (audiometric testing for use in hearing loss prevention program), CSA Z107.58 (noise emission declarations for machinery), CAN/CSA-ISO 5349 (hand-transmitted vibration), and ISO 2631 (whole-body vibration).
This Standard was prepared by the Subcommittee on Noise Exposure Assessment and Control, under the jurisdiction of the Technical Committee on Occupational Hearing Conservation and the Strategic Steering Committee on Occupational Health and Safety, and has been formally approved by the Technical Committee.
This Standard has been developed in compliance with Standards Council of Canada requirements for National Standards of Canada. It has been published as a National Standard of Canada by CSA Group.
This Standard describes methods for determining the occupational noise exposure level of workers (Lex,T) using sampling techniques. Lex,T represents the long-term noise exposure of workers and is calculated from measurements of Leq,t (3 dB exchange rate) in the workplace.
1) The methods in this Standard are based on established definitions, units, instrumentation, and industry practice. Noise exposure has been expressed as % dose in the past. However, the Lex,T should be used, as it is more convenient and less likely to be misunderstood. Refer to Clauses C.1, C.2, and C.4 to convert Lex,T to dose and vice versa.
2) The methods in this Standard normally form part of any occupational hearing conservation program. Users of this Standard should be proficient in noise measurement.
This Standard complements other CSA Group and ISO hearing loss prevention standards (see Figure 2), as follows:
a) CSA Z1007 for guidance to the person(s) responsible for implementing and managing a hearing loss prevention program (HLPP);
b) CSA Z94.2 for hearing protection;
c) CSA Z107.6 for audiometric testing for use in hearing loss prevention programs;
d) CSA Z107.58 for noise emission declarations for machinery;
e) CAN/CSA-ISO 5349-1 and CAN/CSA-ISO 5349-2 for hand-transmitted vibration; and
f) ISO 2631 for whole-body vibration.
This Standard provides methods for measuring the occupational noise exposure from all types of noise, e.g., continuous noise, tonal noise, and impulsive noise. All types of noise (including impulsive noise) are included in a single equivalent sound level for an individual or group.
Note: Although this Standard was written to measure noise exposure in the workplace, it can equally be used to measure non-occupational noise exposures, including those from music players, radios, or other sound reproduction devices.
This Standard can be used to determine the noise exposure level of individuals (Lex,T) or extended to groups (LGroup) with similar noise exposures. It can also be used to measure the average noise (Leq,t) from a given job or activity (e.g., operating a particular machine).
The following subjects are not addressed in this Standard:
a) high energy impulse noise (e.g., such as the noise from nearby gunfire or explosives);
Note: For the purposes of this Standard, high energy impulse noise is any impulse which overloads the instrumentation, typically 137 dBZ for Class 1 and 130 dBZ for Class 2 sound level meters. To measure such sounds, an attenuator can be placed between the microphone and pre-amplifier, the pre-amplifier can be set to be less sensitive (usually by about 10 dB), or a less sensitive microphone can be chosen. However, these measures are beyond the scope of this Standard. Refer to ANSI/ASA 12.7 and Dancer and Franke (1995).
b) underwater noise measurement, which requires different instrumentation from what is used in air; and
Note: More information about underwater noise measurements, but not exposure criteria, can be found in Robinson et al. (2014).
c) noise level surveys.
Note: Such surveys can be a precursor to noise exposure measurements, but in most cases noise exposure measurements as described here are more useful and can be commenced directly without a survey. Guidance on conducting sound level surveys is provided in Annex D.
This Standard provides methods to determine the noise exposure level of workers with a given precision. In certain cases, the user is only interested in determining that a worker’s exposure is above or below the criterion level. Therefore, the methods in this Standard can be less rigorously applied when the noise exposure level is either far above or far below the criterion level.
In this Standard, shall is used to express a requirement, i.e., a provision that the user is obliged to satisfy in order to comply with the Standard; should is used to express a recommendation or that which is advised but not required; and may is used to express an option or that which is permissible within the limits of the Standard.
Notes accompanying clauses do not include requirements or alternative requirements; the purpose of a note accompanying a clause is to separate from the text explanatory or informative material.
Notes to tables and figures are considered part of the table or figure and may be written as requirements.
Annexes are designated normative (mandatory) or informative (non-mandatory) to define their application.