When you say noisy sound, do you mean there is a lot of static, or what kind of noisy sound do you mean?
Select as Best AnswerUndo Best Answer
How are you connecting it? Are you using the amp & speakers of the cassette player to output from the mp3 player?
At a guess your input volume is too high and you're saturating the amp. Try turning the mp3 volume down to it's minimum audible level.