Theres an app called "N9 QTweak" that has a MOD to make volume louder. I use it but Im not sure if it really works.

I was able to improve it by executing (in terminal):

amixer cset numid=16 3

But it seems to only last for that 1 phone call, and may have undesirable effects on the speaker...

My N9 developed very strange issue as of yesterday - call volume through earpiece went way to low even at full power. I can barely hear the other party even in a quiet environment. I do not know if there is a relation, but prior that happened I have toggled "Noise canceling" to ON in Settings. 10 minutes before that I had a normal conversation over phone.
I have tried reboot, toggling OFF/ON noise canceling, cranking the volume up-down, muting, setting speaker ON/OFF. Also I have tried setting alsa earpiece volume to level 3, which improves the situation slightly.
I think I can hear sound coming out of the speaker when in call, not only from earpiece. I can't be 100% sure, as the volume is too low, but I have tested covering the earpiece with finger and I can hear sound which seems to come from the bottom speaker.
Any ideas? I am thinking of messing with pulseaudio. I don't think it is a HW issue as phone had not been dropped and it happened right after toggling noise canceling.

Does the N9Qtweak mod enable it after each reboot?
I also think the mod gets reset after every call.
Someone should write a good workaround for it.
Totally embrassing to miss everything someone is saying while on the road with your superphone

@bibek
There is a script posted above, that checks every 15(configurable) seconds if the earpiece volume is set to max, and if not - sets it. But in my case that is not helping as the volume is way lower than it was prior the "incident". So I am looking for solution to get my earpiece volume back to it normal level.

Checking every 15 mins is too rude way.
One should make it to connect the signal of reboot and call end

@bibek
You are probably right. Anyway - as I mentioned I am looking for solution to get my volume back to its normal state. I am content with it, don't really feel a need for improvement.

bibek,

N9QTweak's tweak for volume increases the volume in alsa-mixer from 66% to 100%; it stays this way till you flash or change the value back; it does NOT change at every end of call or every reboot

Really, I thought the N9QT vol patche was based on all previous I had seen which got reset after call. If this is true I will have to take another look.

@thedead1440
By "increases the volume in alsa-mixer from 66% to 100%" you mean volume of the bottom SPEAKER, responsible for ringing/media playback? Or there is a way to set the EARPIECE volume to 100% as well?