Odd "buzzing" call quality on approx 1 call in 10

I’m using Asterisk 1.2.18. On about 1 call in 10, the caller sounds very strange… like they’re talking through a blown speaker. We can hear that they’re talking but can’t understand them. It is not a choppy sound - more like a buzzing. If they call right back it is often fine. My SIP provider has no suggestions. This happens on calls taken soft phones as well as on calls taken on analog phones using an ATA. The traceroute to the SIP provider seems ok. Does anyone have any thoughts on what I might try? I’m using only ulaw codec for all calls and we have a full T1 with no more than 4 calls at one time.

Sounds like a memory issue, do “top” and see how much memory is free on the box running *

OK thanks - I’ll watch that. Is this a symptom you’ve experienced? Just curious how you came up with that.

Yes, eaxactly that, I found that an mp3 player had created lots of instances and chewed up all of the memory. The symptoms were as you described. Not saying it’s the same in your case, but it’s worth looking at.


A bug in my * box’s BIOS allows only half of my 512MB of ram to be used. In effect I have only 256MB of RAM. There is a BIOS update available to address this which I’ll try later after the close of business. In the mean time, a ‘free’ gives:

~# free
total used free shared buffers cached
Mem: 256192 209404 46788 0 32668 77304
-/+ buffers/cache: 99432 156760
Swap: 979956 2624 977332

and this is with no active calls. So it looks like there is some swapping to disk going on. Hopefully my BIOS update doesn’t go bad and this will help my strange buzzing problem.

If you’re having to swap to disk, things aren’t too good. I look for zero on my systems. Still at least you now have an idea as to what’s going on.
I’d be very suprised if this wasn’t the root cause of the problem


I’ve rebuilt the server with a new motherboard and now have 1GB RAM and no swapping. Fresh install of Salckware 12.0 and asterisk 1.2.22 yet this problem persists.

On about 1 in 10 incoming calls, we can only hear buzzing or static but the caller can hear us ok. If they call right back all is well. I don’t think it is a packet loss problem and it never happens on outgoing calls. It could be a hardware or setup problem… I recycled the CPU and some of the RAM from the old box, and maybe one of the NICs.

I’m using the stock kernel and the ztdummy module. Could recompiling with the 1000Hz option help? (we don’t use Meetme). I’m also using AstShape for QoS. Any thoughts or ideas?