The ultimate guide to ambient noise monitoring: Tools, methods, and benefits

Accurate hearing thresholds can only be obtained in a suitably quiet environment. Subjects can misinterpret test stimuli when there is uncontrolled environmental noise, leading to invalid results or false responses.

Image Credit: Amplivox

It is possible to mitigate these interferences by controlling ambient noise within certain limits; however, this potentially makes the difference between a pass and a referral.

At its most basic level, monitoring ambient noise is measuring the amount of background noise in a hearing test environment. This enables improved diagnosis and treatment outcomes.

Why measure ambient noise?

Preventing interference with test tones

Background noise can potentially interfere with test tones, artificially elevating hearing thresholds. Healthcare professionals may misdiagnose hearing loss or underestimate a subject's hearing ability. Monitoring noise levels can help maintain a controlled testing environment, enhancing the reliability of hearing assessments.

Compliance with standards

ISO (International Organization for Standardization), ANSI (American National Standards Institute), OSHA (Occupational Safety and Health Administration), and other organizations set specific noise level requirements for audiometric testing environments. Monitoring your ambient noise during testing ensures you stay within these limits.

Adjusting test setting conditions where necessary

Should ambient noise be found to exceed acceptable levels, it will be possible to make adjustments by either testing in a sound booth, relocating the test to a noise-isolated area, using noise-reducing headphones, or rescheduling it for a quieter time.

Occupational and mobile audiometry

Noise levels can fluctuate due to conversations, machinery, or outdoor sounds in non-clinical settings like workplace screenings. Continuous noise monitoring is key to ensuring test accuracy in these settings.

Equipment for measuring ambient noise

A sound level meter or sound room microphone is suitable for the monitoring of ambient noise, measuring frequency content in octave or third-octave bands. It is important to note, however, that a degree of ‘measurement uncertainty’ may stem from sources such as equipment or the environment (ambient noise and distractions), or from the subject, method, or tester.

What noise is permissible?

The British Society of Audiology states that “In general, the ambient noise should not exceed 35 dBA” (BSA, 2017). However, maximum permissible ambient sound pressure levels should be maintained in line with (SPL) - BS EN ISO 8253-1, with a number of factors requiring consideration.

Test tone frequency range

Energy at low frequencies masks test tones at higher frequencies, resulting in a risk of noise. This phenomenon is typically referred to as the ‘upward spread of masking’.

Low-frequency test tones necessitate the use of a quieter test environment, while the 500 – 8000 kHz test tone range allows for more ambient noise. This tone range is used for surveillance audiometry.

Earphone attenuation

Maximum permissible ambient SPLs are based on average earphone attenuation, with supra-aural earphones providing the least attenuation and, therefore, necessitating the use of a quieter test environment.

It is also important to note that some listeners will receive less than average attenuation.

How to avoid exceeding noise limits

It is possible to avoid exceeding noise limits by following a number of simple steps.

1. Measure test room ambient noise levels under representative conditions
2. Determine the earphones’ average sound reduction data. This will require checking the audiometer or earphone instruction manual if this data is not in BS EN ISO 8253-1.
3. Calculate any difference in attenuation between the earphone and the typical current supra-aural earphone values found in BS EN ISO 8253-1. This step may require the use of interpolation for octave band attenuation data.
4. Add these difference values to the highest permitted ambient noise levels. These levels are for typical supra-aural earphones, with more information available in BS EN ISO 8253-1.
5. Compare the result with the ambient noise levels measured in the test room.

Ambient noise monitoring solutions

It is possible to monitor the test environment by adding a Sound Room Microphone (SRM) to the test process. This affords testers complete confidence in the quality of their audiometry results.

Amplivox offers several solutions that incorporate SRM technology.

The Anova^™ provides unparalleled accuracy with the option of an external SRM. The microphone should be placed in the test environment, delivering live feedback to alert users if noise exceeds the ‘ideal level’ for accurate measurements and ensuring the best possible test conditions.

The modelONE PC-based audiometer is also available, comprising noise-attenuating headphones and including a built-in SRM.

It is important to note that using an SRM does not remove the need to employ an IEC 61672 Class 2 microphone in line with guidance provided in the HSE L108 'Controlling Noise at Work' 2005 publication.

References and further reading

1. HSE (2015). HSE - Noise: Health surveillance. (online) HSE. Available at: https://www.hse.gov.uk/noise/healthsurveillance.htm.
2. British Society of Audiology (2014). British Society of Audiology - BSA. (online) British Society of Audiology. Available at: https://www.thebsa.org.uk/.
3. ANSI (2019). ANSI-American National Standards Institute. (online) ANSI. Available at: https://www.ansi.org/.
4. ISO (2025). ISO - International Organization for Standardization. (online) ISO. Available at: https://www.iso.org/home.html.
5. OSHA (2025). Occupational Safety and Health Administration. (online) OSHA. Available at: https://www.osha.gov/.

Acknowledgments

Produced from materials originally authored by Amplivox.

About Amplivox

Amplivox creates a healthier future by providing accessible and accurate medical solutions for everyone.

As a manufacturer with more than 90 years of experience, we are proud to be a trusted partner to hearing and occupational health professionals all over the world by delivering a high level of knowledge-led solutions, service and support. We are here to be your preferred audiological and occupational health equipment provider.

Sponsored Content Policy: News-Medical.net publishes articles and related content that may be derived from sources where we have existing commercial relationships, provided such content adds value to the core editorial ethos of News-Medical.Net which is to educate and inform site visitors interested in medical research, science, medical devices and treatments.