Taming excessive noise levels

IEC TC 29 develops Standards to measure noise and lower its negative impact

By Morand Fachot

Noise is second only to pollution in terms of negative environmental impact, a fact often overlooked as it is not as easy to see. Noise is estimated to cost countries huge sums every year: there is evidence that up to 40% of the population within some industrialized countries is affected. IEC TC (Technical Committee) 29: Electroacoustics, work aims to measure and lower the negative impact of noise.

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Negative health and economic impact

Besides provoking hearing problems ranging from mild to total hearing loss, noise has other negative effects on human health.

Research has shown that long-term exposure to excessive noise levels leads to a higher incidence of cardiovascular and other health problems.

Excessive noise may also affect the unborn. Studies in Japan and the US point to a possible correlation between exposure of the unborn to excessive noise in the womb and low birth weight and even birth defects.

Excessive noise may result from high volumes of road or air traffic or from noise in the work place. Its economic impact is severe, with noise-induced hearing loss representing the leading occupational illness in industrialized nations, according to the WHO (World Health Organization).

Measuring noise is the first step

The measurement of airborne sound can evaluate whether or not a noise source is excessive. As well as protecting the environment we live in, such measurement helps to control the risk of hearing damage being caused, including at work.

TC 29 Standards specify the performance requirements of instruments such as audiometers, which are devices designed to measure hearing for diagnostic purposes or for conserving or restoring hearing. Other TC 29 Standards concern head and ear simulators for the measurement and calibration of hearing aids, as well as other test devices.

A number of TC 29 WGs (Working Groups) and MT (Maintenance Teams) develop new or update existing International Standards for sound measurement instruments.

Permanent monitoring stations are also required, for example to measure noise around airports, and new technology means in some cases these can be interrogated remotely, often in real-time.

On the ground and in the air

A clear example of the importance of TC 29 work in the domain of environmental protection can be found in several ICAO (International Civil Aviation Organization) documents. ICAO is the UN (United Nations) specialized agency that codifies the principles and techniques of international air navigation.

Aircraft noise has a significant environmental impact. This has led to operational limitations and opposition to airport expansions/constructions. Reducing aircraft noise on the ground and in the air is a priority for ICAO and the civil aviation industry.

Volume I of ICAO's Annex 16 to the Convention on International Civil Aviation - Environmental Protection. - Aircraft Noise, makes extensive reference not only to IEC 61265, Instruments for measurement of aircraft noise, but also to a dozen other TC 29 International Standards that set out the performance requirements of measurement instruments (precision sound level meters, sound calibrators, microphones, filters, etc.).

Likewise, ICAO's Environmental Technical Manual Volume I - Procedures for the Noise Certification of Aircraft, makes reference to several TC 29 International Standards.

These references demonstrate the significance of the TC's work as well as its contribution to reducing the environmental impact and to the expansion of a major global economic sector.

Alleviating adverse impact

Excessive noise can lead to a range of hearing loss of variable severity. A natural development of the basic work on audiometers has been the preparation of International Standards for hearing aids.

TC 29 has published 13 International Standards for hearing aids in the IEC 60118 series. These cover measurement of electroacoustic and performance characteristics, as well as EMC (electromagnetic compatibility), signal processing for various types of hearing aids and induction loop systems that are installed in public places, transportation networks and other places.

TC 29 has also prepared IEC 60601-2-66, Particular requirements for the basic safety and essential performance of hearing instruments and hearing instrument systems, in the Medical electrical equipment series of International Standards.


TC 29 work has an impact in many fields and requires cooperation with a number of IEC TCs as well as with other organizations, such as ICAO mentioned above.

TC 29 is a supplier of standards to a variety of other TCs as well as a customer of theirs. This reciprocal arrangement applies to IEC TC 87: Ultrasonics, TC 100: Audio, video and multimedia systems and equipment and TC 108: Safety of electronic equipment within the field of audio/video, information technology and communication technology.

IEC TC 62: Electrical equipment in medical practice, and TC 106: Methods for the assessment of electric, magnetic and electromagnetic fields associated with human exposure use TC 29 Standards.

TC 29 is also a supplier of Standards to ISO (International Organization for Standardization) and to its TCs that prepare standards for Acoustics, Noise, and Use and calibration of vibration and shock measuring instruments.

Future work

TC 29 identifies a number of areas that will see significant technological advances in coming years.

Recent developments in cheaper, silicon-based microphones and the ability to modify their characteristics to give a measurement grade device means that options should open up in the future to use wireless distributed arrays of these microphones. This should help provide live ‘noise maps’, which currently are usually generated by software. Future Standards within TC 29 will include these new microphone types. Consideration will also be given to new microphones with digital outputs, and to those with integrated preamplifiers, as well as to new techniques for optical calibration.

In the hearing aids domain, work is starting to focus on the rationalization of ear simulators and at looking at developing new devices for neonates and children.

Given the growing demand for the wide range of devices and systems covered by TC 29 International Standards, and technological progress that require new or updated Standards, this TC is set to have a full agenda in coming years and beyond.

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ANR (active noise reduction) safety earmuffs use electronics to attenuate the low-frequency noise generated by engines, motors, etc. (Photo: Pro Tech Technologies) ANR (active noise reduction) safety earmuffs use electronics to attenuate the low-frequency noise generated by engines, motors, etc. (Photo: Pro Tech Technologies)
ANR (active noise reduction) safety earmuffs use electronics to attenuate the low-frequency noise generated by engines, motors, etc. (Photo: Pro Tech Technologies) Ground crews are submitted to loud noise from jet engines (Photo: With the permission of Rolls-Royce plc, © Rolls-Royce plc 2012)