How to limit maximum volume?


I have heard that some people blow a thunderer whistle at some time during a call, which can result in serious damage to the ear…
I have even heard that some phones have a built-in thunderer whistle (it is used to inform bystanding people that the phone is “off hook” although there is no call connected)

does Asterisk limit the volume somehow?
or are modern headsets not prone to that attack?



I can’t speak for modern headsets but there is no such protection within Asterisk itself. Asterisk generally doesn’t touch the audio or examine it in any way, unless you use something which requires it.

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Asterisk has no ability to put a howler signal on an analogue line. Any howler on VoIP would be handled entirely by the device itself.

VoiIP phones should be designed on the assumption that signals may be at the clipping level imposed by the limited numerical range of the encoded audio. On analogue lines, the line card gain should be set to achieve this, although, in practice, there are standard signal levels and the telephone instrument should be designed to provide an appropriate audio level when presented with those levels.

As audio is always digital within Asterisk, the limited range of the digital encoding should not take audio above a safe level on properly designed phones.