Newsgroups: comp.speech
Path: pavo.csi.cam.ac.uk!doc.ic.ac.uk!warwick!uknet!festival!leeds.ac.uk!news
From: een6njb@gps.leeds.ac.uk (N J Bailey)
Subject: Re: human tone separation
Reply-To: een6njb@gps.leeds.ac.uk
Organization: University of Leeds, U.K.
Date: Fri, 21 Jan 1994 12:47:35 GMT
Message-ID: <1994Jan21.124735.10960@gps.leeds.ac.uk>
References: <2gv5uf$jtp@vixen.cso.uiuc.edu>
Sender: nntp@gps.leeds.ac.uk
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In article jtp@vixen.cso.uiuc.edu, scheirer@osiris.cso.uiuc.edu (Doug Scheirer) writes:
>        Does anyone know how much frequency separation must exist between
> 	sounds for the human ear to be able to discern them? 


The answer to your question is complex, depending upon the time for whch the tone is presented and the presence or absenceo fother frequencies.  From E.Terhardt, 
"Fourier Transformation of Time Signals: a Conceptual Revision" (Acustica, v57 (1985) page 255:

	Using a previously designed expression for the ear's critical
	bandwidth [Zwicker & Terhardt: J.Acoust.Soc.Amer65(5)(Nov'80)]
	and choosing B=(critical Bandwidth)/25 (which is
	about one JND of frequency),...

(JND == Just Noticeable Difference).  In that reference, the following expression for critical bandwidth is given:

	CB=25+75(1 + 1.4f/1000)

where f is the frequency of the tone.

Hope this helps...

--Nick


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Nick Bailey                             Telephone: +44 532 332057
Lecturer in Electronic Engineering      Facsimile: +44 532 332032     
University of Leeds
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