Can not turn off the sound when using SCListener

Question

I use SCListener to listen the input from mic,and use AVAudioPlayer to play the music.They all work will.

However, I found some problem: I try to turn off the sound(Ring/Silent), but the sound effect still be played. ps:I use kAudioSessionCategory_PlayAndRecord to play the music and listen the input from mic,Is it something wrong? Can anyong help?

Thanks Eileen