How to repair Intermitent Message Alert Tone and music on builtin spkr

i have a i phone 4, built-in speaker intermittently not working for the message alert tone and music, but for the ringing alert tone it is working fine. when there is no external speaker attached i cannot adjust the volume for the the internal speaker (no volume bar) and also to the music player there is no volume. but for the ringer alert it is working fine. please anyone can help me with this... muchlly appreciated... thank you in advance.

email me..

dw4jpm@gmail.com