-Check that you enabled exclusive mode in your audio device's properties and that your audio format is 24bit 44100Hz. If you can't change it, try using other device or reinstalling the audio drivers. Worth noting that the recommended is using a headset with a jack connected directly to the motherboard.
According to xuserv, the game looks for 6ch / 32bit / 44.1k | 2ch / 32bit / 44.1k | 2ch / 16bit / 44.1k, if you're audio device doesn't support these audio format it won't make any sounds .