I just got an N9, and am experiencing the same problem.

Call volume is really low. Does anyone have a solution?

I did find:some code that people suggest putting into the /etc/default/ssh file, but can anyone comment on whether it seems like it would work?

while true; do
sleep 15
read emi ema epb << EOF
'/usr/bin/amixer cget numid=16 |sed -n -e 's/.*min=\([0-0]\),max=\([0-9]\),. */\1\n\2/p' -e 's/.* values=\([0-9]*\).*/\1/p'|xargs
EOF
if["$epb" != "$emi" -a "$epb" != "$ema"]; then /usr/bin/amixer cset numid=16 $ema; fi
done&

(from: http://everythingn9.com/increase-the...your-nokia-n9/)