I have always had a problem with the call volume on my N900. Usually I would have to switch to speakerphone because I wouldn't be able to hear through the normal speaker.

I noticed that applying pressure just to the left of the speaker hole with my finger would fix the problem. But when I removed my finger, the sound would go bad again. A number of people on this forum have reported similar problems.

After disassembly I discovered that the speaker isn't behind the speaker hole. Rather, the speaker is to the left of the speaker hole, *exactly* where I had to apply pressure to hear sound.

The electrical connection to the speaker isn't a wire. The speaker has two gold spring arms that extend up and make contact with two gold pads on the other half of the phone when assembled. (see pic).

I bent the arms up at a sharper angle to hopefully increase the contact force between the arms and the opposing pads. The result is that I no longer have any trouble hearing people during a call.

DO NOT DISASSEMBLE YOUR N900 UNLESS YOU KNOW EXACTLY WHAT YOU ARE DOING

It is very easy to break a lot of things in there.

This is, IMHO, a build-quality issue.

EDIT: other posts concerning this same issue:

http://talk.maemo.org/showthread.php?t=46581
http://talk.maemo.org/showthread.php?t=42227
http://talk.maemo.org/showthread.php?t=41646
http://talk.maemo.org/showthread.php?t=37590
https://bugs.maemo.org/show_bug.cgi?id=6063