15-07-2011, 07:20 AM
(15-07-2011, 07:03 AM)fido Wrote: I often listen to Radio 4 Extra as I like to hear some of the vintage programmes they broadcast. This week they have had some episodes of "A Case for Dr Morelle" but the sound quality is appalling. They claim to be restored but I think I could do a better job of removing hiss armed only with a Dolby cassette deck! This mornings broadcast included an irritating hum. Surely the BBC boffins could manage to filter out a single frequency or add an out of phase waveform to cancel out the hum?
You'd certainly think so, but maybe the Beeb (on strike today!) considers Radio 4 listeners to be made of stern stuff, and sufficiently stoic to overcome any handicap in their quest to be informed, educated and entertained!
On another tack, your mention of 'an out of phase waveform' reminds me that some years ago there was a lot of pubicity about noise attenuation of machinery in factories such as printing presses and wood machining equipment by taking the noise, converting it to anti-phase and playing it through speakers so that each half cycle of noise was cancelled out by a half cycle of its mirror image. The demonstrations were impressive, and it was being proposed as a more effective and cheaper alternative to trying to muffle machinery with noise attenuating covers.
I never heard any more about it - maybe it's in use, maybe it didn't live up to its promise?
David
