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Phone line voice effect

This posting is a response to Dave Reidy’s Phone in stereo, phone on stereo post.

Voice over a standard phone line is simply data. In much the same way MP3 files are compressed by removing frequencies that are outside the range of human hearing to reduce file size, telephone transmissions are filtered to remove the frequencies outside the range of the human voice. In order to allow more calls to be transmitted, the frequencies transmitted are limited to a bandwidth of about 3,000 hertz. All of the frequencies in your voice below 400 hertz and above 3,400 hertz are eliminated. That’s why someone’s voice on a phone has a distinctive sound. So if you are looking to re-create that sound you can use band-pass filter set at about 800 hertz and a bandwidth of about two octaves. That will cut all frequencies that don’t fall within one octave below and one octave above 800 hertz. Or you could just put a microphone up to a telephone and hit record.

An interesting side note from wikipedia:
“In his novel, V., Thomas Pynchon writes that a schematic for the band pass filter was the origin for the popular graffiti character, Kilroy.”