Re: Intelligibility of reversed speech, Why? (Jont Allen )

Subject: Re: Intelligibility of reversed speech, Why?
From:    Jont Allen  <jba(at)RESEARCH.ATT.COM>
Date:    Thu, 25 Jan 2001 10:05:35 -0500

T=F3th L=E1szl=F3 wrote: > On Thu, 25 Jan 2001, Ward Drennan wrote: > > Acoustic information in speech is redundant, of course, but certainly= , > > as information (a cue of any sort) was removed or otherwise > > blurred, you would expect the intelligibility to decrease for a given > > S/N ratio. > > > No. Redundancy means that under a given condition (e.g. S/N ratio) you > don't necessarily need ALL the cues for perfect comprehension. That is, > you can remove some cues without decreasing intelligibility. However, > under some other conditions the same cue may be vital. > To put it another way: how can you tell that something you removed from > the signal was or wasn't a cue? My point was that you cannot state this > for sure from examining its effect under only one possible condition, p= ut > you have to examine all possible conditions. > I hope this helps enlight my thinking. I have another problem with the question of redundancy in speech. It is clear there is redundancy in once sense. Language is an entropy con= strained code. If I say "the dog bit the c_t's tail" I doubt anybody would have tr= ouble telling me that the missing letter is "a." Thus speech is redundant. QED However I dont find the above to be very helpful, or enlightened. One sho= uld not be testing with high-context low-entropy sentences. One should be using nonsense words, or other ways to remove such context effects. Miller, Heise and Licten (1950's) did this by showing the subjects a list= that contained the word they were about to hear, and this allowed them to use real words= , yet remove the entropy problem. When one uses high entropy words, then I really wonder if speech is redun= dant. My feeling is that it is not. This feeling is based on the 50 or so years= of articulation testing by fletcher and the gang. See my IEEE review paper on this topic= . (I also have one in JASA.) One problem with redundancy is that what do you do when the two redundant= cues give you different messages? In other words, they are telling you there i= s a problem. This allows one to detect that the SNR is poor, but it just creates confl= ict. It doesn't reduce the error rate. Jont -- Jont B. Allen AT&T Labs-Research, Shannon Laboratory, E161 180 Park Ave., Florham Park NJ, 07932-0971 973/360-8545voice, x7111fax,

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