[Flac] Standard encoding rates?

[Brian Willoughby]

[  > Telephone is nominally 8 kHz mono (i.e. really bad) though I
[  > think the use of digital voice codecs in the last 20 years may
[  > have improved on this a bit.
[
[  Telephone lines (POTS) have a frequency range of 300-3400Hz. That
[  means 7kHz mono should be enough, although 8kHz is generous towards
[  the transition bandwidth/roll-off.

7 kHz would require a tighter brick-wall filter than even CD, are you even  
sure it's possible to go from flat to silent in 100 Hz (between 3400 Hz and  
3500 Hz)?

Almost all telephone connections are digital.  Certainly long distance, and  
probably local as well.  Since that is all sampled at 8 kHz, you'd be reducing  
the bandwidth even further by sampling at only 7 kHz.  In other words, the  
standard sampling rate for telephone voice is certainly 8 kHz.


... and for grins:

[  > AM radio is lower quality (mono) but I don't know what the digital
[  > equivalent would be.
[
[  Just a minor nit-pick: AM radio can be stereo. However its use is
[  almost nonexistent.

Sure, but is AM stereo more or less widely used than dual-FM stereo (where the  
side channel difference signal is FM modulated rather than AM modulated)?

Brian Willoughby
Sound Consulting