[asterisk-users] Listening to Allison voicemail prompt on SIP phone causes [pop] sounds.

[shadowym]

This is something that has been bugging me for awhile.  I have noticed it on multiple systems with different hardware, with and without zaptel cards, and various versions of Asterisk in the 1.2 and 1.4 branches.

A bit hard to describe.  Using a SIP hardphone I log into my voicemail at which point Allison says "you have x messages.....".  There are various other prompts that exhibit the same problem but that is one easy to explain and reproduce one.  The problem is there is a slight 'pop' sound usually during the first syllable of each word.  So the prompt sounds like "y[pop]ou h[pop]ave t[pop]wo me[pop]ssages".  If I dial *43 to do an echo test and Allison says "you are about to enter an echo test....." it's not there so it's only in certain modes this happens.

It's relatively minor and not something people generally complain about but it's definitely there and (at least to me) kinda makes the system seem to be a bit less polished sounding.  I thought it had something to do with the prompts I am using but when I play back the actual files in a sound player I don't hear those pops.  I tried various formats including gsm, ulaw etc. but it doesn't change anything.

Anyone know if this is a documented issue and if so are there any potential solutions