The Sound Sensor can detect both decibels [dB] and adjusted decibel [dBA]. A decibel is a measurement of sound pressure.

dBA: in detecting adjusted decibels, the sensitivity of the sensor is adapted to the sensitivity of the human ear. In other words, these are the sounds that your ears are able to hear.

dB: in detecting standard [unadjusted] decibels, all sounds are measured with equal sensitivity. Thus, these sounds may include some that are too high or too low for the human ear to hear.

The Sound Sensor can measure sound pressure levels up to 90 dB – about the level of a lawnmower. Sound pressure levels are extremely complicated, so the Sound Sensor readings on the MINDSTORMS NXT are displayed in percent [%]. The lower the percent the quieter the soundFor example:

• 4-5% is like a silent living room
• 5-10% would be someone talking some distance away
• 10-30% is normal conversation close to the sensor or music played at a normal level
• 30-100% are people shouting or music being played at a high volume

Test it!

Test the Sound Sensor’s ability to read sound volume:


Connect the Sound Sensor to the NXT.
1. Select the View submenu on the NXT’s display. Select the Sound Sensor icon and the port where you have connected the sensor.
2. Make some sounds into the Sound Sensor and watch the readings displayed on the NXT. Use the sensor to read some sounds around you.
3. How loud do your parents speak? How loud is your front doorbell?

Try Me
  The NXT comes with a Try Me function. Connect a Touch Sensor to port 1 of the NXT and select the Try Me submenu on the NXT to test your Sound Sensor. You’ll get a fun reaction.