Sound issue
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From: J. J. Lodder on 23 Dec 2009 18:02 Rowland McDonnell <real-address-in-sig(a)flur.bltigibbet.invalid> wrote: > J. J. Lodder <nospam(a)de-ster.demon.nl> wrote: > > > Rowland McDonnell <real-address-in-sig(a)flur.bltigibbet.invalid> wrote: > > > > > T i m <news(a)spaced.me.uk> wrote: > > > > > > > real-address-in-sig(a)flur.bltigibbet.invalid (Rowland McDonnell) wrote: > > > > > > > > >300Hz is a `typical highish voice tone' (I hope) > > > > > > > > > When I was with BT we talked of 'voice' paths being from 300Hz to > > > > 3300Hz suggesting 300Hz was a pretty low voice tone (if we are talking > > > > about the same things)? > > > > > > I've no idea what a `voice path' might be - but 3kHz is `overtone' > > > territory for the human voice, not a fundamental. At least, not for > > > anyone pitching their voice in the usual range. > > > > > > Hmm. > > > > > > "In telephony, narrowband is usually considered to cover frequencies > > > 300-3400 Hz." > > > > > > Okay, so I dunno. 400Hz sounds pretty high pitched to me and telephone > > > voices do seem to be missing the lower frequency part of the voice > > > sounds, so I've thought for as far back as I can recall. Don't have a > > > spectrum analyzer handy - if I did, I'd have a look. > > > > For the stereo signal 400 Hz is the roll-over point. > > What roll-over point? <http://en.wikipedia.org/wiki/Low-pass_filter> > > below that the S-component drops with the usual 6 dB/octave. > > S-component? Stereo component? M = L + R S = L - R L = M + S R = M - S (insert /2 where wanted) So, supposing you start with L and R signals, from a stereo microphone for example. Before publishing on disk one would 1) transform L and R to M and S Feed S through a high-pass filter, roll-off 6 dB/oct below 400 Hz, to obtain S'. 2) recombine M and S' to L' and R' This has the effect of making low frequencies mono only. (to be cut horizontally into the vinyl) No real loss, metre waves don't carry directional information, given the size of an average room. That's also why there is little loss in systems that use a single sub-wooofer. > > Bass singers are therefore hardly affected, > > Er? They produce no significant power below 400 Hz. Even if they can go lower almost all the power is in the overtones Jan > Rowland.
From: Adrian Tuddenham on 23 Dec 2009 18:38 J. J. Lodder <nospam(a)de-ster.demon.nl> wrote: [...] > M = L + R > S = L - R > > L = M + S > R = M - S In BBC parlance: M = main S = side -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk
From: J. J. Lodder on 24 Dec 2009 05:20 Adrian Tuddenham <adrian(a)poppyrecords.invalid.invalid> wrote: > J. J. Lodder <nospam(a)de-ster.demon.nl> wrote: > > [...] > > M = L + R > > S = L - R > > > > L = M + S > > R = M - S > > In BBC parlance: > M = main > S = side That also works. I wonder who did the original naming. Mr Philips from Eindhoven may have been involved, Jan
From: J. J. Lodder on 24 Dec 2009 07:19 Rowland McDonnell <real-address-in-sig(a)flur.bltigibbet.invalid> wrote: > J. J. Lodder <nospam(a)de-ster.demon.nl> wrote: > > > Adrian Tuddenham <adrian(a)poppyrecords.invalid.invalid> wrote: > > > > > J. J. Lodder <nospam(a)de-ster.demon.nl> wrote: > > > > > > > Rowland McDonnell <real-address-in-sig(a)flur.bltigibbet.invalid> wrote: > [snip] > > > > > > It does sound like phase reversal on one channel to me - at least, if > > > > > it's the case that the only part of the signal that's common to both > > > > > channels is `vocals' and only the vocals are so affected. > > > > > > > > Reversing the phase on both channels surely makes it worse still. > > > > Seriously though, a phase reversal doesn't afffect the vocals. > > > > It's the basses, below about 400 Hz, that sufffer, > > > > > > The bass will suffer too, but the vocals are often pan-potted mono, so > > > they cancel when the phase of one channel is reversed. > > > > Supposing them to be centred, which is rarely the case. > > What is usually done is putting most of the soloist > > on one channel, and the acompaning instruments on the other. > > Bass below 400 Hz otoh is always centred. > > (because people may need all the power they can get) > > (and because vertical amplitude had to be limited, is vinyl days) > > A listen to a classic Decca recording will show the fallacy of all those > assumptions. Try feeding the signals through a low-pass filter, and see how much S-component you've got left. But you cleary never tried it. The pick up elements of those days just can't handle the large vertical amplitudes. BTW, you can even see it with a magifying glass. The long wavelength wiggles are purely horizontal, Jan
From: Adrian Tuddenham on 24 Dec 2009 08:28
J. J. Lodder <nospam(a)de-ster.demon.nl> wrote: > Adrian Tuddenham <adrian(a)poppyrecords.invalid.invalid> wrote: > > > J. J. Lodder <nospam(a)de-ster.demon.nl> wrote: > > > > [...] > > > M = L + R > > > S = L - R > > > > > > L = M + S > > > R = M - S > > > > In BBC parlance: > > M = main > > S = side > > That also works. I wonder who did the original naming. > Mr Philips from Eindhoven may have been involved, More likely Mr Blumlein of 57, Earl's Court Square, London, S.W.5 http://www.doramusic.com/patents/394325.htm -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk |