The system software detects if the sound chip is being used. If it hasn't been used for a while, power is disconnected from the sound circuitry in order to conserve power. During this shutdown process, a click may be heard from the speaker.
This power saving mode mostly affects the PowerBook 100, 140, 145, and 170. On more recent PowerBook models, it is possible to disable sound entirely by moving the volume to zero in the Sound control panel. Once the volume is set at zero on those models, even the startup sound will not chime. There will be no clicks from the speaker with the volume set to zero since the power to the sound circuitry is always off.
Article Change History:
16 August 1993 - Revised article with information about recent models.
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