Subject: Re: ultrasonic hearing via bone conduction From: =?iso-8859-1?Q?Lars_Bramsl=F8w?= <lab(at)OTICON.DK> Date: Thu, 24 Nov 2005 07:50:56 +0100Hi Rob, I think the audio equipment manufacturers are trying to sell us something we don't need with 96 and 192 kHz sampling frequency. When it comes to air-conducted sound I haven't seen a blind study where subjects could discriminate a 20 kHz and a 40 kHz bandlimited signal. In hearing aids, on the contrary, we are not trying to sell something not needed :-) For air-conducted hearing aids, we see little reason to go beyond 10 kHz, which is probably going to be the limit for some time. After all, most losses tend to increase with frequency, and we don't have audiometric data beyond 8 kHz from ordinary clinical practice. The earmould and real-ear characteristics is also very difficult to control at these small wavelenghts. There is another related issue in hearing aids and that is to protect against ultrsonic sounds from movement detectors, e.g. burglar alarms, automatic doors etc. These devices produce large SPL's starting from say 50 kHz, and this can cause saturation and intermodulation in the hearing aid front-end, which is audible. The boneconduction aspect is interesting but I still wonder if the audibility is due to intermodulation or off-frequency listening rather than 'ordinary' hearing. If anyone has any scientific papers on the topic, please share them with us. Regards Lars Lars Bramsløw Audiology Oticon A/S Kongebakken 9 DK-2765 Smørum Denmark +45 39 13 85 42 Direct +45 39 17 71 00 Main lab(at)oticon.dk http://www.oticon.com -----Original Message----- From: AUDITORY Research in Auditory Perception [mailto:AUDITORY(at)LISTS.MCGILL.CA] On Behalf Of Maher, Rob Sent: 23. november 2005 23:21 To: AUDITORY(at)LISTS.MCGILL.CA Subject: ultrasonic hearing via bone conduction I recently received a query from a colleague about bone-conducted ultrasonic hearing in humans. I also found a prior thread from a couple years ago about ultrasonic perception here in the AUDITORY list. Based on the published literature it seems clear that humans can get a hearing sensation from ultrasonic vibrations coupled to bone. Anyone able to share their experience working with this phenomenon? Any commercial hearing aids in this realm? It is also interesting that some audio equipment manufacturers are starting to spec their loudspeakers into the ultrasonic range based on these findings. Thank you, Rob Maher * * * A few relevant references are: Lenhardt, Skellett, Wang, and Clarke, A.M., "Human ultrasonic speech perception," Science 253 (1991) 82-85 And more recently: "Where'd you get those ultrasonic peepers?" http://www.acoustics.org/press/150th/Lenhardt.html Fujimoto, Nakagawa, and Tonoike, "Nonlinear explanation for bone-conducted ultrasonic hearing," Hearing Research 204 (2005) 210-215 http://www.h6.dion.ne.jp/~fff/documents/pdf/heares.pdf