Subject: Re: Ultrasonic Hearing (via bone conduction!) From: "Scharine, Angelique (Civ,ARL/HRED)" <AScharine(at)ARL.ARMY.MIL> Date: Sun, 27 Nov 2005 12:23:48 -0500I'll admit that I don't know much about this area, but I think that we're missing the point of the original question - which was about ultrasonic bone conduction. I believe that the concept has very little to do with the ability to actually hear ultrasonic frequencies, but rather, the ability to use ultrasonic frequencies to transmit sound via bone conduction. As suggested, these frequencies intermodulate as they travel through bone and the result is supposed to be audible frequencies. There are other uses for bone conduction other than hearing aids. It can be used in telephones and headsets for normal hearing listeners as well. I believe, (and I'm really hoping a more knowledgable colleague will speak up here), that the use of ultrasonic frequencies is being considered as a method to provide a stronger, more veridical reproduction of sound. Angelique -----Original Message----- From: AUDITORY Research in Auditory Perception on behalf of lazzaro Sent: Fri 11/25/2005 1:02 AM To: AUDITORY(at)LISTS.MCGILL.CA Cc: Subject: Re: Ultrasonic Hearing in Music Recording & Reproduction Hi everyone, In the pro audio world, engineers who audition 48K vs 96K often like the way 96K sounds. But whether this has anything to do with hearing ultrasonics is another matter entirely. For example, the same D/A converters, clocked at 96K & 48K, may have fewer sonic problems with clock jitter at 96K. This phenomena might be producing the sonic changes studio engineers report. Conversion hardware is not ideal ... apart from clock jitter, there are other non-idealities that may sound different in the < 20K regime for 48K vs 96K that may be the root cause. To get a sense of what pros are hearing, consider this review of the Pro Tools HD system (very popular in studios today, although many people take the digital outs from Pro Tools and run them through better converters than the ones Digi offers). The review is by Sound on Sound's level-headed Hugh Robjohns. His description of the difference between listening to 96K recordings at 48K and 96K playback rates, using Genelec 1031s for monitoring: The acoustic instruments (violins, violas and guitars mainly) became significantly more 'real'. The system conveyed much more information about the wood of the instruments, their size, movement and relative spatial positioning -- it was as if an acoustic veil had been removed. I know this is starting to read like a hi-fi magazine, but the difference really was that obvious. Whether Joe Bloggs would notice the improvements in your recordings on the £99 ghettoblaster he bought in Currycomets at Christmas is another matter entirely... This was excerpted from: http://www.soundonsound.com/sos/May02/articles/protoolshd.asp --- John Lazzaro http://www.cs.berkeley.edu/~lazzaro lazzaro [at] cs [dot] berkeley [dot] edu ---