Strange sound from engine

I bought a used 08 tacoma with 38k miles on it. It's a base model 4 cyl. regular cab and was the first vehicle I bought. I've had it for about 5 months and it's always had this very low hissing noise when I press the gas pedal at higher speeds. I'm hoping it's not a problem with the gasket but if that's what it sounds like, could anyone elaborate on the issue? Again, it's this low hissing/humming noise (almost a pre-1khz tone) that's hardly noticeable and is overtaken by the sound of the engine as I depress the gas pedal more. It seems to start at about 30mph'ish and up.

 

can you determine where its coming from on the engine, might wanna check the manifold bolts and the bolts where the manifold hooks up to the cat.

 

Yeah, I'd say to check your exhaust manifold and pipe bolt connections.
I've never noticed it on either of my previous 2 trucks ('08 & '09) but that doesn't mean it wasn't there. Engines in new vehicles make all kinds of strange sounds from all the electronically controlled devices. You should hear my Prius carry on AFTER shutting off the engine!

Afterthought, check your air filter housing to make sure all connections are tight and seated properly.

 

I'm not too keen around the engine block, but i'll take a look. Thanks!

 

ive got a similar sound but its only around 50 and up. im not too worried about it becasue my, 99 tacoma, 03 sequoia, and 06 highlander all do that. Dont think its much to worry about, if its not broken then dont fix it

 

It usually doesn't happen until 80k+ miles, but the cat may be toast. After checking for exhaust leaks, have the exhaust backpressure checked. They pull an oxygen sensor and put a gauge on it. High pressure means that the cat is plugging the muffler. The high pressure forces exhaust out the gaskets and sound like a hiss. Eventually the cat will completely plug the exhaust and the engine will not run.

Hopefully, It's just a leak