Re: Ultrasonic Hearing (via bone conduction!)

["Scharine, Angelique (Civ,ARL/HRED)" <AScharine@xxxxxxxxxxxx>]

I'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@xxxxxxxxxxxxxxx 
	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 Â99 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
	---