Very quiet turbo exhaust - LFN sensitivity
 

So, I have a dilemma that most of you will probably think is silly. A while back, before I was working towards a turbocharger. I got a Racing Beat race pipe and a dual tip cobalt exhaust for super cheap. I installed the setup for about a week, and determined that it was way too loud; my ears would ring every time I drove it. I tried sound dampening the trunk and parcel shelf; ears still rang. Tried wearing earplugs; still rang. The weirdest part was, my wife actually didn't think it was that loud...she fell asleep on a 1.5 hr ride with me!

Then I uninstalled the race pipe, and found that even just the cobalt muffler with the stock mid-pipe would make my ears ring after my 30 minute commute to work. Even though it wasn't loud at all, I could still feel a sort of 'pressure" in my ears. Finally, after a lot of research, I concluded that my ears are just stupidly sensitive to low frequency sound, which explains why the dampening and ear plugs didn't help much. I guess now I'm worried that, no matter what aftermarket exhaust I put on it when I turbo, it's going to make my ears ring and eventually lead to permanent hearing loss. I know that the turbo makes it much quieter, but it's my understanding that that applies mostly to high frequency sound, and the low frequencies can still be pretty loud.

Does anyone have any ideas on this? Is it possible that the cobalt just has a particularly pronounced low frequency response, and a different muffler may help? I know the magnaflow is very popular, but I don't know anyone who has one that I could drive and see how it sounds.

Anyway, I know this probably sounds like a ridiculous problem, but if anyone has any ideas, I would appreciate it. Thanks!

is your n/a exhaust even 3" if not who cares. go back to stock until your turbo, then go 3" with the Miataturbo.net Approved Magnaflow muffler.

anything else = instaban.

That's exactly what I've done so far. I was just worried that, if the cobalt was making my ears ring, then a 3" exhaust would be even worse even with the magnaflow. It would be a serious bummer to get the turbo installed and the car running, and then find that I can't drive it without destroying my pansy-assed ear drums.

MKTurbo exhaust with the MT approved muffler.

Turbos cut out drone (and volume) compared to NA. My magnaflow cat / racing beat axle back setup was whisper quiet, all you could hear was turbo intake noise.

Turbo cars are inherently quieter than NA cars, because the turbo acts to break up a lot of the pulses. On my car the intake is quite a bit louder than the exhaust (folks at Miatas@MRLS have described as sounding like a vacuum cleaner going down the straight).

As for the specifics, you'll have to go listen to one in person, no sound file is going to do it justice.

--Ian

n/a vs turbo same cat and catback:

The big MT approved magnaflow is very quiet with a turbo for a 3 inch. You realize when you pull up beside some gawd awful NA car and you cant hear your car over theirs.

I had a OBX dual exit, shitty ebay header(ricelands), and resonated test pipe, and it sounded good and wasn't too loud NA. When I added the turbo, it was a very quiet bass sound (like stock) until the wastegate opened up and you could hear a little bit. Then I manned up and got some Artech.

I've got a 3 foot long 3" resonator attached to a MKTurbo exhaust (big straight through 3" Magnaflow). The last miata guy that rode in my car asked if I was still running a stock exhaust.

I say this to everyone, because it's true:
you want the quietest-est exhaust: go copy EO2K's. It uses the MT approved Maggie and then adds a resonator and cat. It doesn't get much quieter, and that even includes a stock muffler, which rattles like crazy on a turbo car (I actually tried it)

I'm super OCD and extremely dislike loud exhausts, I know the feeling

Every ear has different resonant frequencies. The volume and shape of your ear and inner ear contribute to how many and how strong.

Download a sine wave generator and determine what frequencies sound louder as you scroll through the Hz range.

I suspect you have a resonant frequency matching your exhaust, which is why your wife doesn't think it's loud, but it's torture for you.

How this information will actually help you? No idea.

Put mufflers on your years is what you're saying? :D

yeah that should help. Go to an ear nose and throat surgeon, and have them install a dna identical 3d printed resonating chamber off your inner ears, tuned to the specific frequency that your muffler booms at.

done.

Guys,

Thanks for the responses! I really appreciate all the input; Brain's comparison video was especially helpful to hear the difference the turbo makes. So the general takeaway is that a very quiet, non-droning, free-flowing exhaust is achievable. Sound's like a cat will be necessary, which is a slight drawback, since I enjoy the idea of going catless just to piss the liberals off ;-)

This would be awesome.

Thanks, I may see if MK Turbo can set me up with something similar :-)

This does make sense, and somehow I feel like it may help, if for no other reason than to satisfy my curiosity :-P

Haha! When you put it that way, it just seems so simple.

Update...sine wave generator indicates noticeable peaks at about 95hz and 120hz...I feel like this should be useful somehow...

Is there anyone in the Columbus/Indy area with what they would consider to be a pretty quiet turbo exhaust? It probably would be good to hear one in person if I can...

I have a 3" pipe to rear, then spliced it into the stock muffler. its dead silent.
looking to rebuild my muffler to take a 3": and gut the thing but thats down the track.

ie. i cut the flange off the original 2" section and welded it onto my 3" pipe.

DEAD SILENT

I took out the package tray and put pink, houseing fiberglass in the two chambers either side of the gas tank. Absorbed almost all of the remaining noise from the 3", Magnaflow muffled exhaust, as well as transmission and diff noise.

​​​​​​​$1400 and I can have a manifold, turbo, and full exhaust delivered to your door next Thursday morning. I will be driving up through Indiana on my way to Michigan City.

I'm sorry, I just have to say that installing a 3" exhaust and then plugging it with a stock muffler is just plain dumb.

It is a data point, but not one that should be utilized.