Remove hum when recording sounds

To remove the mains electricity hum when recording with Snooper, you can apply a pre-recording filter. The hum is usually present at frequency 50 Hz or 60 Hz so a high-pass filter or a notch filter should be fine.

Removing the hum would significantly improve the quality of the recording and make triggering more accurate.

Measuring the frequency distribution with the built-in frequency analyzer with no filter shows:

Frequency analyzer – no filter

Set the filter to a high-pass filter with a cutoff-frequency of 200 Hz.


This will attenuate the hum at 50 Hz and the harmonic at 100 Hz with approximately 20 dB.

Frequency analyzer – high-pass 200Hz


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Snooper Professional with two tone triggering

New version of Snooper Professional 2.2.3.

It’s now possible to use frequency triggering with Snooper Professional.

Four different modes to choose from:

  • Two-Tone Sequential – Triggers on a Two tone paging signal.
  • Single tone – Triggers on a single frequency.
  • Dual tone – Triggers on two combined tones.
  • DTMF sequence – Triggers on a series of DTMF tones.

Many pagers and control systems use some sort of audio tones to activate. The most common type are two tones that are sent in sequence, mostly referred to as Two-Tone Paging or Two-Tone Sequential.

Using Snooper Pro it’s very easy to setup a recording that is triggered by a Two-tone sequence.

Snooper Professional