[Audacity] Telephone Effect

[reteo]

Good point. I forgot about that. :-/

[reteo]

One thing you might also want to add if adapting this technique for old-fashioned radio (AM receivers, which had similar sound)... before actually going through the equalization, you might also want to add some faint pink noise; every old-fashioned radio I've ever listened to had mild static at a low level---not enough to affect the clarity of the sound (for the time), but enough that it became noticeable between songs.

This is because of background radiation; radio-wave radiation naturally exist in a static form; the idea is that radio and television transmitters were built with sufficient power to "punch through" the background radiation, thereby becoming listenable when picked up by an antenna. This is why radio and television signals become more faint the further from the transmitter you get, and this is also the reason you get static on channels where nobody's transmitting locally.

I have also remembered watching one flash animation where it demonstrated the frequency range of receivers through time; it seemed almost like each decade added one or two frequency bands on the high and low end of the sound, until the last two decades where speaker technology became capable of outputting sound throughout the entire human-audible spectrum (20Hz to 20Kz), so it's safe to widen the audible channel as the period recommends.