Sony NEX-3 Instruction Manual page 182

Beep
Selects the sound produced when you operate the camera.
1 [Menu] t [Setup] t [Beep] t desired setting.
AF Sound
High
Low
Off
The audio signals will sound only when the subject is in focus,
and during self-timer countdown.
Turns on audio signals when you press the control wheel, or soft
keys.
If you want to lower the volume, select [Low].
Turns off the audio signal.
GB
99