The NXT Sound Sensor measures the intensity (volume) of sound using the microphone on the face of the sensor. For example, you can use the sound sensor to make your robot react to a loud sound such a hand clap.

Sound Sensor Data

The Sound Sensor can give the following data:

Data	Type	Range	Notes
Sound Level (dB)	Numeric	0 to 100	Sound level, scaled to a percentage (0-100%)
Sound Level (dBA)	Numeric	0 to 100	Sound level, adjusted to approximate human ear sensitivity, and then scaled to a percentage (0-100%)

The Sound Level (dBA) value is adjusted to approximate the sensitivity of the human ear to different frequencies. This means that sound frequencies that are heard by the sensor but are hard for you to year will not result in a high sound level value.

Tips and Tricks

Quiet sounds and normal talking usually result in sound levels less than 50%. A hand clap or loud voice will usually produce a level greater than 50%.

Examples Using the Sound Sensor

Some examples of how you can use the NXT Sound Sensor in your program are shown below.

Example 1: Start Your Robot with a Clap

This program makes your robot start driving when you clap your hands. It uses the Wait block in the Sound Sensor – Compare – dB mode to wait until the sound level rises above 50%.

Example 2: Sound Controlled Speed

This program makes your robot drive forward, with the speed of the robot controlled by the sound level. The louder you yell at the robot, the faster it will drive! The program uses the NXT Sound Sensor block in the Measure – dBA mode to get the sound level on a Numeric data wire. The result is wired to the Power input of a Move Steering block to make the sound level control the motor power. The process is repeated in a Loop so that the motor power is continuously adjusted based on new sound readings.

Blocks that Can Use the Sound Sensor

The table below lists the different programming blocks that can be used with the NXT Sound Sensor. Each block will have different modes for the dB and dBA data provided by the sensor.

Block	Mode	Use
Wait	Sound Sensor - Compare	Wait for the sound level to reach a certain value.
Wait	Sound Sensor - Change	Wait for the sound level to change by a certain amount.
Loop	Sound Sensor	Repeat a sequence of blocks until the sound level reaches a certain value.
Switch	Sound Sensor	Choose between two sequences of blocks based on the sound level.
NXT Sound Sensor	Measure	Measure the sound level and get the result on a Numeric data wire.
NXT Sound Sensor	Compare	Compare the sound level to a threshold and get the result on a Logic data wire.
Data Logging		See Data Logging.

Using the NXT Sound Sensor