This has to do with the AGC functionality in 3.1(3). It tried to raise all the recording to the specified target dB level (i.e. -26 or there abouts), including silence. In it's efforts to do that it magnifies the background hiss (or comfort noise) which is what you're hearing there.
In Unity 3.1(4) the AGC stuff was enhanced to be smart enough not to touch it if the volume is lower than a set level (-40 by default) and to not raise it more than a set amount (10 dB I think by default) to avoid this problem.
If you can't upgrade to 3.1(4) then you'll have to turn off AGC on this system if you want that problem to go away... however this will introduce other problems that I'm sure you're familiar with involving varrying recording volumes coming from different internal/external sources and the like.
The short answer is that you don't.... That isn't entirely true while at
the same time it kind of is, but for the most part you don't configure
the softkeys. You enable or disable them via TCL. Here is the long
answer. Be sure to read the whole thing or e...
Topology: IP Phone > Switches > Microsoft NPS setup to forward 802.1x
proxy to > ISE 2.1 patch 3 Authentication: EAP-TLS using Cisco MIC SANs
Phone Models 802.1X support? 802.1x flavor Addtl Comment EAP-MD5 EAP-TLS
Cisco 3905 Y Y N Cisco 6911 Y Y N Cisco ...
This document describe how DST changes and how time changes are
implemented in DST. Daylight Saving Time (DST) is the practice of
setting the clocks forward 1 hour from standard time during the summer
months, and back again in the fall, in order to make b...