IOS 4.0 Vumeter Not run in Device where as working well with simulator

Question

Hi

i am developed VUmeter functionality with live radio streaming. it's working well when i run into simulator version 4.0 but in device(3GS,4.0) its not working i am not getting updated values of audiolevels. suppose at first time when method call i got value levels: 0.001817, peakLevels: 0.005463 its remain same not changed whereas in simulator same code working well.

levels[0] = self.audioLevels[0].mAveragePower ;

peakLevels[0] = self.audioLevels[0].mPeakPower ;

suggestion or advice require...