First , let us know what emulator your using , personally i prefer Project 64 as i have never had any problems with this as i have used it on many computers over many years.
You may also find in the set-up options different sound drivers , if you use a different codec it may give a good result on your PC.
Also are all the games doing the same thing? you may have a bad ROM .
Also are what are your PC stats? do you have enough power to run the emulator at full speed ?
Computer is just a pain without a real controller to work with. Sigh
i use my Nintendo 64 controllers on my computer , i have a $10 n64/PSx to USB converter that works great i use it for all my emulations
Here is a link to look at it , this is an Australian site however i am sure you could find one in what ever country you live in.
http://www.consolemate.com.au/playstati ... p-471.html