[asterisk-users] Silk for Free

[Wilton Helm]

>12kHz isn't really enough for high quality voice, and the extra bit 
>rate needed to push the bandwidth to 15kHz is small. Also, a deep man's 
>voice looses something when you cut off at 70Hz. 

I'm not sure that this isn't stretching things a bit.  There are no handsets or headsets (AFAIK) that can do justice to 50 KHz and probably most speakers attached to a PC can't.  Likewise, while a deep male voice can go below 70 Hz, few transducers can do justice to those frequencies, either.  I don't think the attempt is to reproduce a symphony.  The extra bandwidth (even if it is minor) would be hard to justify if one needed $500 speakers to benefit from it.  While a number of people might be able to tell the difference in an A B comparison, I suspect few would notice it without direct comparison.  I also suspect Skype is correct in that the majority of people, listening to it on typical hardware would like additional low frequencies less than without because of things like distortion in the transducer.  

Getting the bandwidth above 3 KHz at the top will improve intelligibility, but somewhere between 5 and 10 KHz that reaches a point of diminishing returns.  Likewise, extending the low end below 300 Hz will help naturalness, but that also reaches diminishing returns somewhere around 100 Hz unless all the pieces are very high quality (from the mic to the speaker).  It seems to me that they have exceeded those realities by a comfortable margin, which is generally what good engineering is all about.

Wilton
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