Quite true on wideband audio response and the necessary
amplification that must follow it.

Working around stray RF fields can cause other problems
around electret microphones. They are inherently high-
impedance so one has to pay attention to the VLF and up
stray RF because of that high impedance...especially if
using newer op-amps or other active devices having high
frequency amplification. It is a compromise in design:
attenuate the VLF and above response but hold the
microphone amplifier response flat out to at least 10 KHz.
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You probably mean the last line to be ...........not more than approx 3
kHz. After all we talk 'phone' operation.

Frank GM0CSZ / KN6WH ( from W6 back in chilly GM )