Subject: Re: the autocorrelation function for measuring the F0 From: "Richard F. Lyon" <DickLyon(at)ACM.ORG> Date: Thu, 28 Jul 2005 20:34:59 -0700--============_-1089514363==_ma============ Content-Type: text/plain; charset="us-ascii" ; format="flowed" At 1:10 PM -0700 7/28/05, Stefan Crawcour wrote: >When calculating the F0 from the speech sample, I automatically use >the autocorrelation function. But, what does the autocorrelation >function really do? Is it a similar mechanism as in the FFT >(multiplying the speech sample with an appropiate window, if I am >not terribly mistaken) ? It's not clear what you mean when you say you "use the autocorrelation function." Speech does not, in general, have an autocorrelation function, which is defined as a function of a stationary random process, or of a finite signal (with bounded energy); speech is neither. What you're probably doing is a short-time autocorrelation, which is defined for signals of finite duration, or for segments of signals made finite by windowing. Here's some stuff google finds for short-time-autocorrelation-function: http://shay.ecn.purdue.edu/~ee649/homework/hw3.pdf http://home.netnam.vn/elib/index.asp?progid=305&page=41&id=40876 http://www.nis.sdu.dk/~marcela/NIS04/week-40/lesson_4.pdf It is not unusual for the phrase "short-time" to be omitted, thereby confusing the issue. To answer "what does it really do?": it computes of the ACF of the windowed signal, which might be what you were wanting to verify. Or was it? Dick --============_-1089514363==_ma============ Content-Type: text/html; charset="us-ascii" <!doctype html public "-//W3C//DTD W3 HTML//EN"> <html><head><style type="text/css"><!-- blockquote, dl, ul, ol, li { padding-top: 0 ; padding-bottom: 0 } --></style><title>Re: the autocorrelation function for measuring the F0</title></head><body> <div>At 1:10 PM -0700 7/28/05, Stefan Crawcour wrote:</div> <blockquote type="cite" cite>When calculating the F0 from the speech sample, I automatically use the autocorrelation function. But, what does the autocorrelation function really do? Is it a similar mechanism as in the FFT (multiplying the speech sample with an appropiate window, if I am not terribly mistaken) ?</blockquote> <div><br></div> <div>It's not clear what you mean when you say you "use the autocorrelation function." Speech does not, in general, have an autocorrelation function, which is defined as a function of a stationary random process, or of a finite signal (with bounded energy); speech is neither. What you're probably doing is a short-time autocorrelation, which is defined for signals of finite duration, or for segments of signals made finite by windowing.</div> <div><br></div> <div>Here's some stuff google finds for short-time-autocorrelation-function:</div> <div><font face="Lucida Grande" size="-3" color="#000000">http://shay.ecn.purdue.edu/~ee649/homework/hw3.pdf</font ></div> <div><font face="Lucida Grande" size="-3" color="#000000" >http://home.netnam.vn/elib/index.asp?progid=305&page=41&id=4<span ></span>0876</font></div> <div><font face="Lucida Grande" size="-3" color="#000000" >http://www.nis.sdu.dk/~marcela/NIS04/week-40/lesson_4.pdf</font></div > <div><br></div> <div>It is not unusual for the phrase "short-time" to be omitted, thereby confusing the issue. </div> <div><br></div> <div>To answer "what does it really do?": it computes of the ACF of the windowed signal, which might be what you were wanting to verify. Or was it?</div> <div><br></div> <div>Dick</div> <div><br></div> <div><br></div> </body> </html> --============_-1089514363==_ma============--