mikegarrison

That's also my assumption. (I was kidding about losing his hearing.) The range of sound levels that people deal with is phenomenal. That's why sound is measured on a log scale. A sound wave with twice as much pressure as another sound wave is barely detectable by the ear as being louder.

Just like the "butt dyno", people tend to hear what they want to hear. Or what they fear to hear, in this case.

Measure it objectively, if you really want to know what's going on.

sparky2000

Thanks for the input so far - a lot think I am getting used to the noise.

I really don't think it's that as it is REALLY quiet, also I have asked friends
to listen and they think it is way lower.

I have an AEM CAI fitted earlier this year which produces a good sound and over
the months, it didn't seem to get any quieter.
i.e. my ears didn 't get used to the sound.

The drop off in noise from the Saturday to the Tuesday was huge so can't be explained
by "human error" so to speak.

It also feels down on power although this is hard to quantify.
i.e. if it now puts out 200bhp due to some damage, it is still a quickish car.

I suppose ideally I need another S2000 in a straight line to see if I fall behind.

I just can't see it being my ears / other ears, it is car related.

This brings me back to finding a problem that has me really confused.

Xviper - you mentioned the cat might be damaged, I really hope so.
Would it not have a warning light if damaged or could it appear ok yet be
strangling air-flow?

I suppose my last question is all you guys with Amuse fitted, have any of you
broken them through driving (not a car crash). If the answer is no, then
the odds of it happening to me must be tiny and it's another part of my car.

mikegarrison

What you are talking about are two things that are MEASURABLE. Sound is measured with a sound level meter. Power is measured with a dyno. There is simply no reason to not get data. But it's your car, and your problem. Solve it the way you like.

xviper

Not necessarily. It depends on what the O2 sensor is reading. You can strangle your exhaust by stuffing a potato in your tail pipe(s) and you wouldn't necessarily get a CEL.

speed4tu

I have to agree with xviper, all my exhausts tend to get louder over time never quieter. Did you check to make sure there was no cardboad or styrofoam inside the header before you installed it? Maybe something got clogged int the cat. You could always get a test pipe and forget about the cat. Plus it would give you some more sound.

S2kRob

Well, all I can qualify it with is that after a couple of days, the low rpm resonance quieted down noticeably. High rpm stayed about the same. And yes, I do think the exhaust has gotten a little louder since I've bought it, but really not much.

GodoftheBOLP

You've gotten used to it, my invidia system doesnt seem loud to me anymore either... But everyone else around me thinks its loud shit.

TubeDriver

My Amuse got louder after a few thousand miles. I bet you had some styrofoam packing in the header (that was not removed before installation) and it got blown into the cat and than melted. Pull your cat and check the front to see if there is any obstruction.

Road Rage

I support the opinion that exhausts tend to get louder as the packing settles, because there is less effective surface area. My thinking is that the sound waves are converted to heat in the mufflers, converting their sound energy to thermal energy. As the packing gets "beat down" like one of those "UFO" crop patterns, the muffler becomes less effective at the conversion. Just my opinion.

However, I did measure the 1 meter SPL of my Mugen when I had just installed it, and then after 1000 miles, and it had picked up several dB, as well as becoming more basso. Just love the sound now.

mikegarrison

Well, your opinion happens to be correct. Generally speaking, car mufflers are what we call "bulk absorbers". The plane waves travelling down the exhaust pipe reach a perforated tube with a space behind it. The space is filled with some fibrous material. The sound energey gets into the fibers, causing them to vibrate. That energy turns in to heat. So sound energy -> heat energy, and the sound gets quieter.

Over time those fibers will break down and/or become contaminated. As that happens they lose the ability to turn the sound into heat, so the muffler loses effectiveness. The fibers break down; they don't "break in".

And it's nice to hear about someone actually measuring their sound levels before commenting on them.