Subject: Bill Cole: Speech-shaped noise From: Dan Ellis <dpwe(at)EE.COLUMBIA.EDU> Date: Mon, 21 Feb 2005 11:08:53 -0500Dear List - I am forwarding a response from Bill Cole of Etymonic/Audioscan concerning issues in generating "speech-shaped noise". DAn. ------- Forwarded Message From: Bill Cole <bill(at)etymonic.com> Subject: Speech-shaped noise Date: Sun, 20 Feb 2005 14:00:32 -0500 Dear Richard: Speech-shaped noise will not do you much good since it is unmodulated. You also need to be specific about the frequency shaping that is applied to the noise since the ANSI S3.42 shape is intended to represent the spectrum of speech peaks whereas the shapes in ANSI S3.5 (and used for the ICRA signal) is representative of the LTASS of speech for various vocal efforts. If you have the facilities, I would suggest taking a short (10 - 15 s) passage from a recording of everyday speech and filtering it to produce the LTASS you want. Alternately, you might consider the ICRA digitally-modified speech signal (www.icra.nu/ITEMS/ICRAnoise.htm ). It has some shortcomings but it gives results similar to real speech for any aids I have tested It is not just the signal that matters but also the way in which it is analyzed. If you really want to know what is going on with digital hearing aids, you need to use real speech as the test signal with analysis parameters that permit comparison with behavioral measures of hearing. If you have the capability to perform 1/3 octave spectral analysis, I would suggest setting your analysis parameters to yield 128 or 256ms analysis blocks to approximate the integration time of the ear. We sell a product (Verifit) which accomplishes these goals. You can read about it at www.audioscan.com and in the October and November issues of the Hearing Review at www.hearingreview.com . If you care to contact me directly, I can provide some additional technical details of the signals we use and their analysis. Regards, Bill Cole ------- End of Forwarded Message