You feel more than a little annoyed with iPhone's speaker volume. Yes, whether you're waiting for a call, trying to have a speakerphone conversation, or just listening for sweet DTMF tones -- the thing kind of stinks. Perhaps it's time to take extreme measures, as some owners have resorted to... like sticking a needle through the holes in the speaker enclosure. Yes, according to daring "modders," it's possible to get a 40% increase in volume via this simple-yet-destructive trick of perforating the thin plastic which covers the speaker. Apparently, the phone gets so loud post-surgery that the volume is actually startling to some users.

But you need to void the warranty in order to do that....

Source- http://www.engadget.com/2008/01/18/iphone-speaker-too-quiet-stab-it-with-needles/