[Elecraft] [K3] Noise Reduction Recording

[David Woolley]

Trevor Smithers wrote:

> What you really need is a method of identifying the actual ssb speech waveform, extracting the noise 
> from it leaving the signal in the clear. There is a company in Germany that produces an outboard unit 
> that I find very effective without the degradation in the audio. Audio demo here  
> http://www.home.vrweb.de/michels/sound_demo.htm

The web site isn't exactly forthcoming about how it really works, even 
though they claim to have a patent (personally I think patents go 
against the spirit of ham radio).  Lingua suggests a voice tract model, 
but the talk of envelopes doesn't seem consistent with that.

Incidentally, MP3 is not a good format for representing noisy signals. 
The compression algorithm assumes that the signal has strong spectral 
peaks which greatly exceed the noise.  It actually suppresses parts of 
the spectrum, where it thinks the sound is dominated by adjacent 
spectral peaks.

In general, noisy signals are difficult to compress. Sound will show a 
bias towards zero, so will be partially comprssible.
> 



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David Woolley
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