HVAC help please - need air exchange while keeping sound in!

Hi all, I've almost finished building a home studio underneath my house. I've followed the advice on this site (and in books) as much as possible and (although not fully tested yet) expect to have pretty good sound isolation. The studio is for home practise and recording - I expect to end up with professional quality recordings but don't expect to have a full rock band or anything in there. The room is roughly 13' x 10' x 7' I live in a quiet neighbourhood. I'm more worried about noise getting outside and annoying neighbours than I am about having external noise spoil my recordings. Regarding HVAC, I have left the final design until now, although I have been researching it since I started and had an acoustic/ sound proofing company come in and advise (they advised me to do (a) and (b) below). The room is relatively air tight, which is great for sound isolation, but not great for ensuring fresh air exchange. Although a ducted system is ideal, it simply wasn't an option for me. Too expensive and, more importantly, the roof is too low. So the plan is to put some sort of air flow system in once the main construction was completed - i.e. air coming in somewhere and leaving somewhere else. My current thinking is: (a) Use the AEROPAC system on one wall to force fresh air from outside into the room. The rated 'Air Movement' is more than enough for the size room and the flow is extremely quiet. You can see more detail at this website: http://www.acoustica.com.au/aeropac.html (b) Have a vent on the opposite wall to allow air to leave the room. HERE LIES MY PROBLEM. I can easily put a vent through one of the walls, but will destroy the sound isolation. My research suggests that having piping with a few right angles in it (before it gets outside) and some sort of sound absorbant lining inside the pipe, will maximise sound loss coming in or going out. Has anyone done this successfully? what are the rough guidelines? any construction ideas? Alternatively I could install TWO AEROPAC's?? One going in and one leaving? I spent a long time searching this site but couldn't find any design ideas for a fresh air vent. I'm sure there are some ideas here somewhere, though, so if anyone can direct me to them that would be great! Otherwise, if anyone has ideas that aren't yet posted - please help! I'd like to keep the project (excluding the AEROPAC, which I have already bought) to under $500, but will go up if a good solution can be found. Any help will be greatly appreciated! Cheers Bruce