PURPOSE: To demonstrate that doubling the sound intensity creates a change of 3 decibels in the sound intensity level.

DESCRIPTION: Divide the class in two, ask one half to make some noise (eg. clapping), and note the SIL. Then ask the whole class to make the same noise, raising the sound intensity level by 3 dB.

SUGGESTIONS: When you tell them what to expect they can easily adjust their noise to give a 3 dB difference.

See Question of the Week #149 and #150 for information on using this demonstration to enhance class involvement.

REFERENCES: (PIRA unknown.)

EQUIPMENT: Sound level meter, mounted TV camera and monitor.

SETUP TIME: 5 min.