Where can I find a device that measure the noise level?
 

I'll be organizing competition where the winners will be based on how loud people applaud for each participant. To be fair and unbiased, I need an instrument that will measured the noise level when people applaud/scream.

I know such an instrument exist but don't know what's its called nor where to get one!

decibal meter any local radio shack or along those lines where you live. Cheap device

You should be able to find them at any store that has vehicle sound systems and whatnot :)

which they will be double as expensive since they use highly precise equipment for judging those competitions.

Cool, there are a few Radio Shacks near my house, I'll be checking them out.:thumbsup

If that doesn't pan out then those workplace safety supply stores that most major cities have should stock them.