Let's say that AAC encoded 44100 sampling rate signal is transparent at 128 kbps stereo.

Does anyone have any suggestions regarding the transparency bitrates for sampling rates other than 44100 Hz, like 16000 Hz for example?

Daniel

Transparent at 16 KHz? The lowpass would be at 8 KHz which is far from being transparent.

Let's put it this way: suppose you have original sound sample recorded at 16 kHz sampling rate. What would be the lowest bitrate you would use to encode it to AAC and to achieve that encoded AAC audio would still sound the same as original sample?

Daniel

You must mean the source of human voice. I don't think it's proper to record music @ 16 k Hz. I'll use 20 kbps with LC-AAC Core for that purpose.

Where does your conclusion come from? Listening tests?

I think 20 kbps is pretty low bitrate for 16 kHz stereo. My calculation gives me 50 to 60 kbps for stereo. I haven't checked it subjectively yet.

Daniel

Edit:
And no, I don't mean speech only. Many music samples don't contain much high frequencies. For example chech horn sample at http://sound.media.mit.edu/mpeg4/audio/sqam/.