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Acoustic Shock

You may be familiar with the term acoustic shock but believe that it does not apply to you. The fact is that any telephone operator is at risk from its causes and effects.

Telephone headsets are capable of delivering wide bandwidth sound at a level that is a risk to hearing health.

This risk can be from two causes:

  • Noise exposure over prolonged periods of use.
  • Short duration sudden loud sounds.

ITU-T Recommendation, page 10 defines Acoustic Shock as "Any temporary or permanent disturbance of the functioning of the ear, or of the nervous system, which may be caused to the user of a telephone earphone by a sudden sharp rise in the acoustic pressure produced by it" - this is the classical acoustic shock.

It is thought that the long term dose of sound is more insidious. The potential damage is more gradual. It also makes users more sensitive to sudden loud sounds.

Australian "Standards"

AS/ACIF S004:2013, Australian Standard, Voice frequency performance requirements for Customer Equipment

This document supersedes Standard AS/ACIF S004:2008.

The requirements in this Standard are consistent with the aims of s376 of the Telecommunications Act 1997. Specifically these aims are:

  • protecting the integrity of a telecommunications network or facility
  • protecting the health and safety of persons who are likely to be affected by the operation of the network or facility to which the equipment or cabling is connected
  • ensuring equipment can be used to give access to an emergency call service
  • ensuring interoperability of equipment with a network facility used to provide the standard telephone service

Section 5.4.3.8.1 Table 3 of this document states that the maximum RMS (ie continuous) level, when using a headset, shall be 118dBA. The maximum instantaneous level shall be 123dBA. Acoustic sounds of these levels are capable of causing acoustic shock to users.

This Standard describes in great detail how the testing is to be undertaken to validate compliance.

It also refers to Australian Communications Industry Forum (ACIF) Guidelines - in particular "ACIF G616:2013 Acoustic safety for telephone equipment".

A copy of this Standard can be found here.

National Standard for Occupational Noise NOHSC: 1007(2000)

This National Standard, published by the National Occupational Health and Safety Commission specifies an eight-hour equivalent continuous sound pressure level of 85dBA.

Currently the Commonwealth, the Territories and all the States except South Australia require that workers shall not be exposed to an eight-hour equivalent continuous sound pressure level of more than 85dBA per day on average during a five day working week. South Australia has set a limit of 90dBA.

This document also states:

"The levels specified in the national standard are the maximum acceptable exposure levels for noise in the workplace. However, over long periods, repeated noise exposure at between 75 and 85 decibels may be a small risk to some people. With progressively increasing levels, the risk becomes greater. Workplace noise levels lower than 85 decibels are, therefore, desirable, if practicable."

ACIF G616:2013 Acoustic safety for telephone equipment

This Industry Guideline deals with issues and circumstances that affect the topic of acoustic shock that are outside the Standards AS/ACIF S004:2013 and AS/ACIF S042.1. This Guideline contains additional information about acoustic safety and should be read in conjunction with the above standards (i.e. AS/ACIF S004:2013 and AS/ACIF S042.1).

Please note that:

"This guideline is advisory only. It does not form part of the AS/ACIF S004:2013 Standard or the AS/ACIF S042.1 Standard and is not legally binding."

This guideline suggests generic steps and measures intended to help organisations reduce the risks of acoustic shock.

This Guideline provides a comprehensive understanding of acoustic shock and related issues.

This document states that the maximum sound pressure for instananeous sound should be set at 102dBA.

Furthermore,

".. conforming to the specified maximum sound pressure levels does not ensure that the sound levels received by telephone users will be less than an eight-hour equivalent continuous sound pressure level of 85dBA SPL or sufficiently low to avoid noise induced hearing loss following long term use."

A copy of the full ACIF G616:2013 Industry Guideline can be found here