Rome meeting of International Commission on Non-Ionizing Radiation Protection discusses HEFUA's work (23 March 2016)

ISVR Professor meets in Rome with International Commission on Non-Ionizing Radiation Protection 

23 March 2016

On 23 March 2016 Professor Timothy Leighton met in Rome as part of the International Commission on Non-Ionizing Radiation Protection (ICNIRP) working group on Ultrasound where discussion was made on the safe use of all types of ultrasound. As part of this activity, Professor Leighton presented his findings on the issues surrounding the requirement for guidelines for safe use of ultrasound in air. This follows the publication in January 2016 of an article in the Proceedings of the Royal Society A identifying mass exposures of the public in public places, the inadequacies of current guidelines, and the growth of technological uses for ultrasound in air. ICNIRP is well aware of the need to distinguish such ultrasound in air (extending very roughly between 20-100 kHz)  from the generally higher frequency (roughly 1000 kHz and higher frequency) ultrasound in tissue, for which the mechanisms of hazard are based on heating tissue, stimulating bubble activity, and subjecting tissues to radiation forces. For ultrasound in air at the levels Prof Leighton's team had measured in public places, these would not be the mechanisms for any health effects, and this (along with the very different propagation characteristics) meant that a clear distinction was necessary. Professor Francis Duck and Professor Leighton would begin writing a report about ultrasound in air which the other members of the group agreed would be very useful.

The working group accepted Prof Leighton's proposal to set the lower limit of ultrasound for the purposes of producing safety guidelines at 17.8 kHz, his argument being that this was the lower limit of the third octave band centred on 20 kHz: if one set 20 kHz as the lower limit of ultrasonic frequencies, as was usually done, the 'guideline 20 kHz level' actually applied all the way across the third octave band, and so was the level at 17.8 kHz. All previous '20 kHz' levels that had been set therefore, unknowingly, set the levels for 17.8 kHz, and therefore to make this peculiarity explicit, it was logical to set the lower limit at 17.8 kHz. This definition also allowed better hand-shaking with regulations set for audio frequency sound, because of the use of third octave bands between frequency regimes, although because much of audiofrequency work focused on frequencies below 8 kHz, it was vital that the 8-17.8 kHz range was not ignored.

Dr Zenon Sienkiewicz, chair of the working group noted the need to bring knowledge of devices and their outputs up to date (Professor Leighton has presented spectra from a range of devices) and Professor Leighton explained that he had a plan to work with a highly respected publisher in acoustics to produce a Special Issue of their journal on the topic of Ultrasound in Air. This would attract authors who would, in their manuscripts, fill in the knowledge gaps to a certain extent.

These actions were agreed by all as a very positive way of filling the knowledge base for, and providing the structure for, future guidelines from ICNIRP on the safe use of ultrasound in air. 

Other resources

  • Click here for the HEFUA site. 
  • Click here for the project page at the Institute of Sound and Vibration Research.
  • A review published by the Royal Society on guidelines, standards, emitters and the possibility of adverse effects on humans as a result of ultrasound in air from commercial devices is available for free click clicking the PDF icon at the web page here

A video showing how smart phones and tablet computers can be used by members of the public to detect ultrasound in air is available here (further explanation is given in Appendix A of this paper). We invite you to take such measurements and post them (with details of where and when the recording was taken, with what device, app and settings) into the feed found here by following us on Instagram @Ultrasonics_at_Southampton and post your own using the hashtag #UltrasoundInAir. The complete feed to date can be seen by clicking here.