Copyright 2010 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.
The following article appeared in J. Acoust. Soc. Am. 128 1 , July 2010 and may be found athttp://link.aip.org/link/?JAS/128/EL8 .
If that link doesn't work, I'll just email it to you.