The sound sensor introduced in MaxMon app version 1.3.0 uses the phone's built-in microphone to monitor the volume of ambient sound (Note: it cannot record or replay audio).

The sound sensor records sound pressure in kilo-decibel-seconds (kdBs):

  • Decibels (db) measure instantaneous sound pressure (see Wikipedia).
  • A 'very calm room' is about 20-30dB, while a handheld electric mixer is about 65dB.
  • The MaxMon sound sensor measures accumulated (not instantaneous) sound. So 50dB for 100 seconds = 5000 dB-seconds, or 5kdBs. This is more useful than only measuring the instantaneous sound pressure every 10 minutes (the default MaxMon log interval), which could miss a bomb going off (if the explosion lasted less than 10 minutes :).
  • When you see a spike of accumluated sound in a MaxMon report it could be due to a loud sound of short duration, or a quieter but longer sound. This ambiguity is reduced when you see multiple readings. Basically prolonged, elevated sensor readings mean more noise!
  • You can configure alerts for when your monitored location is too noisy ... or too quiet.

 Calibration

  • The microphones of different Android devices can vary significantly, so you'll need to monitor your sound sensor to decide what readings constitutes 'loud' or 'quiet'.
  • Most Android devices have an upper limit on their microphone readings (designed for speech), so don't expect to distinguish between food mixers and jackhammers.
  • You may see occasional dips in the sound sensor readings in the email report graphs. These occur when alerts or reports are sent and the sound sensor has not 'accumulated' for a full log period. If you look at data table you should see a shorter interval between readings.
  • The MaxMon sensor being an accumulator (described above) is why its readings slowly increase on the "Settings>Sensor" screen of the MaxMon app. Clap, sing or shout to see the value increase more quickly.