Poor Audio Quality From Exchange 2010 UM

Question

Hi,
I'm experiencing an issue with our Exchange 2010 Unified Messaging system in that the audio quality is suddenly rather poor.  We are using Cisco Callmanager 7 for our phone system.  When you call an automated attendant, hit the "messages"
button or call the extension to go to voicemail, the audio you hear "crackles," or sounds like it is skipping slightly in that there are brief but noticable interruptions in the audio.
The audio quality issue only occurs when you are connected to voicemail or automated attendants, but not when conversing to other people on phone calls, so that leads me to believe either some interoperability between CM and Exchange UM is malfunctioning, or
just something in UM is a problem.  Also, if you listen to voice messages through the computer instead of over the phone, the quality is fine.  The problem seems to be mainly with calling in to the UM system.
What can I do to properly troubleshoot this?  I have found the Exchange 2010 UM Troubleshooting Assistant, but I have to wait another 2 weeks before I can install Service Pack 1 due to downtime window restrictions.  I'm not coming up with a lot of
documentation involving this, so if anyone has any information they think might help me get to the bottom of this I would apprecaite it.
Thank you.

Answer 1

Cisco Callmanger and UM are on the same LAN.
I highly doubt that QoS is the culprit here, simply because there aren't any issues with phone calls.  If QoS was dropping VOIP packets, then IP phone to IP phone calls would also have poor audio quality.  If I call somebody on another IP
phone on the LAN, the audio quality is perfect.  It is only when you are connected to the UM system that you hear the poor audio quality -- either listening to voicemail prompts, listening to actual voicemails, listening to the automated attendant --
anything in which UM is on one end of the phone call.
It also seems strange that this is somewhat intermittent.  When the issue first occurred, it was definitely happening every time you called in to the UM system and I could repeat the issue by simply pushing my messages button and listening to the welcome
and prompt for a PIN.  I restarted the Exchange server at night, and the next day it was intermittent with people calling the help desk to say they were getting poor audio quality from UM but when I tried to repeat the issue I could not.
I also have users complaining of intermittent slowness when using Outlook, which may be totally unrelated.  I have been running Perf logs on the Exchange server for the last couple of weeks othe CPU, Network Connections, Exchange RPC totals, etc.
and can't find anything that is using too many resources.