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Ultrasound in public places – our first JASA publication!

Beth and Jack are excited to announce the publication of their paper “Measurements of Ultrasound from Public Address and Voice Alarm Systems in Public Places” in a special edition of The Journal of the Acoustical Society of America on the topic of Ultrasound in Air.

Following on from previous measurements of ultrasound emissions from data projectors in schools, this paper presents measurements of ultrasound in public places such as train stations, shopping centres, galleries, and museums, and explores the difficulties encountered when using conventional sound level meters to measure very high frequency tones.

Measurements of ultrasound were made in public places with a hand held microphone

The results of the investigation support the theory that public exposure to ultrasound is widespread; tones were identified in the 20 kHz third-octave band at 8 of the 14 locations tested and the characteristics of the noise was consistent in each case with its source being a Public Address or Voice Alarm system.

Identifying high frequency tones in an FFT analysis

As there is currently a dearth of guidelines for public exposure to ultrasound based on robust scientific evidence, it is hoped that the measurements presented in this paper may be compared with future guidelines to determine whether ill effects on members of the public are likely.

At Apex, our mission is to help improve the built environment.  We value knowledge and care about the potential for public harm from the design of our surroundings.  That is why we are proud to spend our time, effort and expertise to contribute to this field of research and continue to promote strong links between industry and academia.

The following article appeared in J. Acoust. Soc. Am. 144, 2548 (2018) and may be found at

Measurements of ultrasound in public places JASMAN_vol_144_iss_4_2548_1

Copyright 2018 Acoustical Society of America. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the Acoustical Society of America.

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