How much can you hear the turbo with a stock setup?

Short version of the story: Take car (2006 Outback XT 5MT with 50k miles) to a respected indy for an oil change. They change the air filter without my permission - I drive the car, and the turbo is much louder than before - Under boost the whoosh of the compressor is much louder, and the blowoff noise is much louder when I release the accelerator. I'm familiar with the causes of these noises, and I've never heard going from a dirty to clean air filter causing this huge change in other turbo cars I've owned or worked on. I bought the car with 42k miles - so my question is for anyone driving a stock Legacy GT (or OBXT) and who owned it when new or at least when it was in good condition in stock form - how much can you hear the turbo under boost? Prior to this, I could barely hear it - now it's very loud. I checked the boost level, there are no leaks downstream of the compressor and the car runs great, so this would have to be a leak between the airbox and compressor or else the air filter restriction has a huge influence that I've never heard in other cars.

This is not uncommon. Many have switched from paper to an AVO filter, such as me and could hear the turbo spool. I wouldn't call it a disturbing sound by any means. Also, any garage should let their customers know whenever they change/replace something.

Yes with added air flow you will gain a little extra noise. Check to make sure they have the air box fully seated properly and everything is tight. Some shops aren't too good and putting stuff back the way they found it.

When I bought my car, I added an AEM dry air filter. No turbo wooshy noises. Ditched the catted up pipe for a catless one. Wooshy noises!

 

So yeah, I'd be more upset about a repair done w/o my authority.

Yes with added air flow you will gain a little extra noise. Check to make sure they have the air box fully seated properly and everything is tight. Some shops aren't too good and putting stuff back the way they found it.

 

This. So many times with my older subarus the shop monkeys never fully seated the airbox before tightening the clamps and would leak. Probably the same issue here I'm guessing and make sure they actually put an air filter back in there.

Thanks for the replies...I removed the airbox, checked there was actually a new filter in there, and reseated and tightened everything I could see. Didn't change the noise. Yes I was pissed about the unauthorized work (they took the charge off the bill), the drastic increase in noise for some as yet unknown reason, and the small puddle of oil on my driveway and oil all over the under engine shield due to sloppy work (I checked the drain plug is dry and tight, filter is tight but was covered in oil, oil level is correct). They will be getting a call from me Monday morning.

That's why I've moved to changing my own oil. Too many stupid uncalled for mistakes at dealerships and shops.

Problem has been resolved - the shop installed an OEM Subaru air filter to replace the new filter they put in (possibly Wix) and the turbo is back to its normal quiet operation. I'm still surprised the air filter could make such a huge difference but it did - stick with OEM and all is well.

I replaced my parking lights with LEDs the other day and found a previous owner had done this to the airbox...no wonder it's quite loud

 

http://i.imgur.com/SX7aREPl.jpg

I replaced my parking lights with LEDs the other day and found a previous owner had done this to the airbox...no wonder it's quite loud

 

http://i.imgur.com/SX7aREPl.jpg

 

loudness aside...it probably added 10-15HP! #winning

When I changed my dirty air filter I was surprised at the difference in sound... noticed the BPV immediately, with a solid increase in induction noises. Went from OEM to OEM on a completely stock intake. The old filter was pretty leaf-clogged, though.

Glad you found out the sound, I went a different route with Blitz.