is there a way to increase the volume on calls made from an SIP user?
nevermind
in case anyone else is wondering
rxgain for received volume -and-
txgain for transmit volume work well
Increasing Volume means you are increaing the amplitude of the sound packet.
I haven’t seen asterisk having any settings for this perpose.
Have you searched the voip-info wiki?
I am thinking about dynamically increasing or decreasing the volume during the call. 
hmmm since i am using SIP clients tied to zap channels volume can be controlled via the pc or in my case blackberry.
i required the overall gain of the zap channels to be increased and the above functions peform this action… thanks for your input though 
using SIP clients tied to zap channels volume can be controlled via the pc
What about calls made from an analog hanset that doesn’t have
volume control?
Is there any function in asterisk for the same?
Or is it I am asking for more 
unfortunately i personally do not know of any asterisk functions that can control the volume of any acitve channels…
however the zapata.conf file can be modified to adjust both the transimitted and received volume of each individual zap channel, this however requires a reload of asterisk.
Hi hammonduser,
Thanks for your reply.
The zapata.conf can be configured in database using Realtime Static.
Using AGI script the table containing the zapata configuration can be
changed to reflect the required rxgain and txgain values.
Yes, and as you said it would require a reload of chan_zap.so that
reads from the zapata.conf