If you are using the on-board sound, then we need to know what motherboard you have. In most, but certainly not all, cases the audio chip will be a Realtek derived device. However, we need to be absolutely certain so that we can provide you with the correct information.
Download and install CPUID - System & hardware benchmark, monitoring, reporting
Run the program and select the Mainboard
tab. The information we need can be found in the location that I've highlighted.