Subject: Re: Intermediate representation for music analysis From: Ilya Sedelnikov <ilyas@xxxxxxxx> Date: Wed, 19 Jul 2006 21:45:03 +0300Hi, Could you give me some references to people/articles that make use of this technique ? In fact, this is exactly the technique I use to improve the frequency resolution of the constant-Q filterbank. Ilya Quoting Hugh McDERMOTT <hughm@xxxxxxxx>: > I would add to this that, using an FFT, it is quite easy to measure the > component frequencies of a complex signal with precision that is finer > than the bin spacing. One just needs to estimate the rate of change of > the phase of a component within a bin. This technique, which has been > described in the context of the so-called phase vocoder algorithm, > permits the frequency of each signal component resolved by the FFT to be > estimated more precisely than the limit apparently imposed by the FFT > bin spacing in the frequency domain. > > Best regards, > > Hugh McDermott, PhD > Principal Research Fellow > Department of Otolaryngology > The University of Melbourne > 384 - 388 Albert Street, > East Melbourne. 3002 > Australia. > Phone: +61 3 9929 8665 > Fax: +61 3 9663 6086 > E-mail: hughm@xxxxxxxx > Web page: http://www.medoto.unimelb.edu.au/people/mcdermoh/ > > > -----Original Message----- > From: AUDITORY Research in Auditory Perception > [mailto:AUDITORY@xxxxxxxx On Behalf Of Bob Masta > Sent: Monday, 17 July 2006 11:01 PM > To: AUDITORY@xxxxxxxx > Subject: Re: Intermediate representation for music analysis > > Note that no matter what sort of analysis you do, the frequency > resolution is determined by the reciprocal of the analysis window > duration. So if you want fine resolution for the low frequencies, you > need a long sample set, even if you only need much coarser resolution at > the high frequencies (due to the log nature of hearing). > So, why not just take a long FFT? Even though they have linear > frequency spacing, FFTs have been heavily optimized for efficient > computation. I wonder if it might be better using a conventional FFT > and lumping some upper bins together to form quasi-log bands, rather > than using a less-efficient log-spaced filter bank. > > There is one weakness to that approach, however, in that if you set the > overall FFT length so that the lowest band you want to handle is just > exactly matched by the lowest FFT spectral line width, then the next > spectral line will be at *twie* that... there will be no nice > fractional-octave alignment. If you really need that, > a log filter bank may be best. > > However, the way I have seen this handled is to assume (hope?) that > there will be plenty of upper harmonics in the signal, many of which > will fall into regions of the FFT where the resolution (considered on an > octave basis) is much higher. By looking at a few of these upper > harmonics, it was possible to figure out what the actual fundamental > frequency was to similarly-high resolution. > > Best regards, > > Bob Masta > > audioATdaqartaDOTcom > > > +++++++++++++++++++++++++++++++++++++++++++ > This Mail Was Scanned By Mail-seCure System > at the Tel-Aviv University CC. > ---------------------------------------------------------------- This message was sent using IMP, the Internet Messaging Program.