Design a band-pass filter from its lower and upper cutoff frequencies.
The centre frequency of a band-pass filter is the geometric mean of its cutoffs, not the arithmetic mean, because filter response is logarithmic in frequency. Q is the centre frequency divided by bandwidth. Telephone audio uses roughly a 300 to 3,400 Hz band-pass, giving a Q of about 0.32 — a very wide filter by comparison with radio tuning.
Band Pass Filter
Centre frequency = √(f_L f_H); bandwidth = f_H − f_L; Q = f₀ ÷ bandwidth
Centre frequency = √(f_L f_H); bandwidth = f_H − f_L; Q = f₀ ÷ bandwidth The centre frequency of a band-pass filter is the geometric mean of its cutoffs, not the arithmetic mean, because filter response is logarithmic in frequency. Q is the centre frequency divided by bandwidth.
Telephone audio uses roughly a 300 to 3,400 Hz band-pass, giving a Q of about 0.32 — a very wide filter by comparison with radio tuning.
This calculator takes 3 inputs: Lower cutoff frequency, Upper cutoff frequency, Signal frequency. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.