I was in the same exact boat as you using the HDMI to my DVI monitor and left with no sound
,Then found out a cheap simple solution that works for headphones and speakers
. First you need this cable and you may already have it because it comes in the PS3 box packaging. -http://www.amazon.com/gp/product/B003U7WCEM/ref=oh_details_o01_s00_i00?ie=UTF8&psc=1
Then you will need this adapter to allow you to connect a 3.5mm (headphone jack style) plug into the RCA. -http://www.amazon.com/gp/product/B00A4EFYPI/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1
Then you're done. However that is all that you need if you are only using headphones. If you want to plug sound into a TV/speaker then you will have to buy this cable to turn 3.5mm female in a male connector with this simple cable. -http://www.amazon.com/iMBAPrice-iMBA-PS-06MM-6-Feet-Plated-Stereo/dp/B009UEAZ84/ref=sr_1_2?s=electronics&ie=UTF8&qid=1388523831&sr=1-2&keywords=3.5mm+male+to+male+6ft
It works 100% because I have the same exact setup and bought these cables to get sound and works perfectly and was very inexpensive compared to buying a receiver to plug into the optical jack.