Something you quickly learn when you first become an audio enthusiast is that this field is full of dense jargon. For example, if you heard someone talk about “squelch” in an audio receiver, what would you think that refers to, other than maybe some kind of unpleasant wet noise? Fortunately, the “squelch” has nothing to do with wet noises; Rather, it is a feature found on most audio receivers that keeps the audio channel closed when nothing is playing.
If you’ve ever listened to music through cheap speakers or headphones, you may have noticed a distinct and potentially unpleasant ambient hiss or buzz when there is no music or video audio playing. If you’ve heard this, it’s probably because you’re listening on a device with little or no squelch functionality, or the squelch setting is set too low. It’s thanks to the squelch settings that those quiet moments between tracks in your playlist are actually quiet and not just a ringing in your ears.
Squelch keeps audio channel closed when nothing is playing
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An audio receiver, when turned on, always receives some sort of signal from the device connected/plugged into it. Simply plug a pair of headphones into your phone to open the audio channel, even if no music is playing. This is why you may hear a slight hiss or buzz when your headphones are plugged in: the channel is open and the speaker is receiving input, but that input is essentially just the audio equivalent of breathing.
That’s where squelch comes in. Whether through your smartphone’s audio settings or a physical button, receivers can set a squelch threshold that activates when no signal of sufficient strength is detected, that is, when no actual sound is being transmitted. When the signal strength is below the squelch threshold, the receiver’s audio channel is closed, preventing extraneous noise from filtering through.
Technically, Squelch features can be found on any audio receiver, especially one equipped with an equalizer or an equalization app like AutoEQ. However, they are most commonly found in two-way radio systems. Empty, unnecessary noise can clutter an open radio channel, so using squelch is important to ensure clean transfer of conversations. This is part of what makes a walkie talkie such an essential tool for campers and hikers, for example.
