Rick Lyons wrote:> On Thu, 15 Jan 2004 07:53:36 -0600, Richard Owlett > <rowlett@atlascomm.net> wrote: > > >>Rick Lyons wrote: >> >>>On Sun, 11 Jan 2004 15:22:59 -0600, Richard Owlett >>><rowlett@atlascomm.net> wrote: >>> >>> >>> >>>>[SNIP] >>>>Actually I suspect I need to know more about "windowing". >>>>Any references besides a book coming out in March ;> >>> >>> >>>Hi Richard, >>> >>> there's a decent two-part tutorial on windows at: >>> >>>Part I: >>> >>>http://www.e-insite.net/tmworld/index.asp?layout=issueTOC&pubdate=6/1/1998 >>> >>>I just noticed the website now requires your E-mail >>>address before they'll give the Part I article. >>> >>>Part II can be found at: >>> >>>http://www.reed-electronics.com/tmworld/index.asp?layout=article&articleid=CA187573&rid=0&rme=0&cfd=1 >>> >> >>A totally unbiased opinion ;? [ actually I liked it] >>I'm wondering if a rectangular window might be fine for what I'm doing >>at the moment as I was looking at logical ways to combine data in some >>number of adjacent bins. My sample rate is intrinsically fixed at 4 to >>10 times Nyquist. > > > Hi Richard, > > > ah shoot. I'm not sure what you're > doing. A rectangular window is the > same as not windowing at all. > > [-Rick-] >CONTEXT: I have an interest in speech recognition at the VERY end user level. I've been "bugged" by comments on comp.speech.users about how "acoustically clean" the environment must be for good results. Past fleeting casual contact with DSP suggested that should not be such a significant problem. That led to an interest in characteristics of speech. My investigation has meandered into paths that may not have much correlation to anything in speech recognition. It's an advantage of avocational investigations -- you don't have to produce "useful results" :} I wanted to start from a reproducible base. I have a CD set of Alexander Scourby reading the _Bible_ . This gives me many hours of one voice recorded under studio conditions sampled at 44kHz. TASK: Examine speech to get a 'feel' of how it varies in time. METHOD: Plot a 3D surface of frequency spectrum as function of time. [ I can't get feel of spectrograms that seem to be popular in the speech recognition field, so I'm doing it my way ;] To create these plots: 1. do FFT on chunk of data (currently 1 second chunks), save it 2. repeat on chunk offset by some constant (currently 50 msec) 3. plot So really my question should be restated. If I'm interested in frequencies from ~300 Hz to ~5 kHz, do I have any need to apply a window function. Also, my frequency resolution is excessive due to the externally determined sample rate. I think some sort of running average over adjacent bins might clean things up visually without destroying too much information. Also considering plotting frequency on something approaching a log scale. Clearer, or just muddied waters more ?
To 'sinc' or not to 'sink'
Started by ●January 11, 2004
Reply by ●January 16, 20042004-01-16
Reply by ●January 18, 20042004-01-18
Jerry Avins <jya@ieee.org> writes:> [...] > In DSP, the form with pi is more generally useful and far more > common.Jerry et al., Bet you thought this was dead, huh? I just noticed tonight that Pawlak et al. define "sinc(t) = sin(t)/t" in their article "Postfiltering Versus Prefiltering for Signal Recovery From Noisy Samples" in the December 2003 issue of IEEE Transactions on Information Theory. Maybe this definition is more widely used that you or I thought? -- % Randy Yates % "Midnight, on the water... %% Fuquay-Varina, NC % I saw... the ocean's daughter." %%% 919-577-9882 % 'Can't Get It Out Of My Head' %%%% <yates@ieee.org> % *El Dorado*, Electric Light Orchestra
Reply by ●January 18, 20042004-01-18
Randy Yates wrote:> Jerry Avins <jya@ieee.org> writes: > >>[...] >>In DSP, the form with pi is more generally useful and far more >>common. > > > Jerry et al., > > Bet you thought this was dead, huh? > > I just noticed tonight that Pawlak et al. define "sinc(t) = sin(t)/t" > in their article "Postfiltering Versus Prefiltering for Signal > Recovery From Noisy Samples" in the December 2003 issue of IEEE > Transactions on Information Theory. Maybe this definition is > more widely used that you or I thought?Until I started hanging out with you DSP guys, it was the only one I knew. In DSP, the pi scaling makes sense. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●January 18, 20042004-01-18
Jerry Avins <jya@ieee.org> writes:> [...] > In DSP, the pi scaling makes sense.It's a matter of putting pi one place or the other, so I don't see either one making more sense than the other. I simply harped on it because I thought it was the Universal Definition (TM), but I was wrong (again)... -- % Randy Yates % "She's sweet on Wagner-I think she'd die for Beethoven. %% Fuquay-Varina, NC % She love the way Puccini lays down a tune, and %%% 919-577-9882 % Verdi's always creepin' from her room." %%%% <yates@ieee.org> % "Rockaria", *A New World Record*, ELO
