Randomly the game seems to crash the sound driver and all sounds become extremely loud and distorted. A feedback noise starts, which then gets louder until the point that it can damage speakers/headphones - seems like a full sound card shutdown. Might this be to do with number of audio channels selected? This problem can only be fixed by rebooting/shutting down the system.
Not sure if it's related but there are soundfiles always playing in the background, for example a zombie scream, or a can opening. Sometimes the sounds are looped continuously but do not play in full, e.g. the zombie scream plays repeatedly but only the first half second or so.