How Does Sound Activated Recording Work?

sound activated spy camera

A common question asked about sound activated recording spy cameras is how it works and how loud of a sound does it need before the triggers the recording mechanism.

For example, if someone was moving about in a room would it begin recording or would the sound have to be louder. On the other hand, would passing cars outside the house activate the recording.

The microphone in these devices are constantly listening for sound and when the volume reaches a predetermined dB level it starts recording. Depending on your situation sound based recording could be a great benefit. The other options would be motion based recording or thermal motion sensing recording.

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To get a better idea of what a dB level is, take a look at this chart of common decibel levels.

Decibels (dB) Degree Sound Source
225 Deafening 12″ Cannon @ 12′ in front and below
195 Deafening Saturn rocket
180 Deafening Aircraft at take-off
160 Deafening Ram jet
150 Deafening Turbo jet
140 Deafening Artillery fire
130 Deafening Threshold of pain, decibels at or above 130 cause 

immediate ear damage. Hydraulic press, pneumatic rock drill

120 Deafening Riveter, chipper, thunder, diesel engine room, fireworks
110 Deafening Punch press, close to a train, ball mill
100 Very Loud Passing truck, home lawn mower, car horn @ 5 meters, wood
saw, boiler factory
90 Very Loud Decibels at or above 90 regularly cause ear damage. Noisy
factory, truck without muffler
80 Loud Noisy office, electric shaver, alarm clock, police whistle
70 Loud Average radio, normal street noise
60 Moderate Conversational speech
50 Moderate Normal office noise, quiet stream
45 Moderate To awaken a sleeping person
40 Faint Average residence, normal private office
30 Faint Recording studio, quiet conversation
20 Very Faint Whisper, empty theater, ticking of watch
10 Very Faint Threshold of good hearing
0 Threshold of excellent youthful hearing

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