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[OT?] what's a FPGA?

Started by Richard Owlett March 22, 2006
Jerry Avins wrote:
> rickman wrote: > > ... > >> BTW, I know you want to do it "your way", but sampling at 44 kHz will >> not give you any extra useful information that you won't get at 8 kHz. >> The phone company is not dumb and they realized a long time ago that >> the range of frequencies required to carry intelligible voice is less >> than 4 kHz. The higher frequencies do not add much to the picture, but >> will require a lot more power to analyze. Have you found any content >> in the higher frequencies that others have not? > > > I find that intelligibility of speech -- even screechy soprano speech -- > is hardly impaired by my hearing loss. I can't hear the top two notes on > a piano. Now that's a brick-wall filter!
/ begin chuckle I'll see your "normal" hearing loss and raise you my *abnormal* loss / end chuckle I look for wider than telco land line bandwidth for 2 sets of reasons: A1. I've read articles saying telco speech is "intelligible" but it is easier if higher frequencies available. The distinguishing features of consonants are in the higher frequencies. *HUMANS* automatically resolve ambiguities based on context (several layers of?). A2. If I read correctly, speech recognition tends to use _AT MOST_ the first three formants (~150 -> ~1300 Hz) for vowels and presumably some similar range for consonants. B. I have a "good" ear and a *BAD* ear ;) "Bad ear" degraded due to scars on ear drum and nerve damage related to childhood ear infections. B1. If enough points are recorded, the response of my "bad ear" resembles a "picket fence" [Guess what a lifer seargant said when I took an *ENLISTMENT* physical with a bunch of _DRAFTEES_ during Viet Nam ;] B2.
> > Sampling at 44.1 will make recursive filters easier and transversal > filters harder. Given Richard's view that he needs linear phase, 44.1 is > asking for trouble. In his place, though I would plan to sample at > around 12 KHz or, if it's enough simpler, 22.05. You can't tell that the > high end isn't useful unless you have it. > > Jerry
"Richard Owlett" <rowlett@atlascomm.net> wrote in message 
news:123dj14mgtn4d44@corp.supernews.com...
> Jerry Avins wrote: >> rickman wrote: >> >>> BTW, I know you want to do it "your way", but sampling at 44 kHz will >>> not give you any extra useful information that you won't get at 8 kHz. >>> The phone company is not dumb and they realized a long time ago that >>> the range of frequencies required to carry intelligible voice is less >>> than 4 kHz. The higher frequencies do not add much to the picture, but >>> will require a lot more power to analyze. Have you found any content >>> in the higher frequencies that others have not? >> >> >> I find that intelligibility of speech -- even screechy soprano speech -- >> is hardly impaired by my hearing loss. I can't hear the top two notes on a >> piano. Now that's a brick-wall filter! > > I look for wider than telco land line bandwidth for 2 sets of reasons: > > A1. I've read articles saying telco speech is "intelligible" but it is > easier if higher frequencies available. The distinguishing features > of consonants are in the higher frequencies. *HUMANS* automatically > resolve ambiguities based on context (several layers of?).
This is easy to verify by having someone say a long set of random letters over the phone while you try to right them down. You might be surprised how poorly the accuracy is, especially in discriminating pairs such as s/f, v/z, p/t, etc.. This problem is probably also part of the reason the military uses the "alpha, bravo, charlie..." alphabet for spelling out things. So while the human brain does a very good job at understanding normal speech from context clues over a limited frequency channel, additional high frequencies make it much easier on the brain (and hence less tiring for long conversations). There is certainly a matter of diminishing returns, but in my experience, even extending from the normal phone high frequency response to 4-5 kHz makes a substantial difference.