iOS AVAudioRecorder record失败的问题

self.audioRecorder = [[AVAudioRecorder alloc] initWithURL:audioRecordingURL settings:[self audioRecordingSettings] error:&error];
[self.audioRecorder prepareToRecord];
[self.audioRecorder record];

在模拟器上prepareToRecord和record都返回YES,但是在真机上record返回NO,请问可能是什么原因？