WRX STi noises

[Mark Carroll]

I know that with the tires and the lack of soundproofing I should
expect a reasonable bit of noise from my 2004 STi, and indeed it
seems comparable to other performance cars so I'm not worried, but
I'm curious about what it is that actually makes the sounds.

Two obvious ones are: there's one periodic sound whose frequency is
clearly proportional to the wheel speed, and I wonder if its frequency
is indeed exactly the wheel rpm. I heard just the same in an Infiniti
G35 I borrowed recently. I'd thought it was from the tires, but now
I'm thinking, shouldn't the tire noise be uniform instead of having a
periodicity? So what would be making the periodic sound?

Also, there's a clear hum when I'm cruising at maybe 75mph or so, that
I only get in a narrow speed range, as if something's being vibrated
at its resonant frequency. Any idea what that might be?

I don't mind the noise at all - I expect a bit of noise from the STi,
as it's optimized for performance, not quietness - I just found myself
getting to wondering where the noises actually come from, when I was
driving into work this morning, and I realised I didn't know the
answers and probably you guys do.

-- Mark

 

[Mike Lloyd]

Do any of those noises vary with terrain?

I moved recently and noticed a strange sound on the drive home. A "hum" at
62-66 MPH -- no more, no less -- on a newly paved blacktop surface over a
long causeway. I really freaked until I realized that, for whatever reason,
it only occurred right on that 3 mile stretch of road at those specific
speeds. I let off the clutch and it went away making me think it was
tranny; turns out that if the car was slowing through those speeds that the
noise wasn't present, during acceleration of stead pace, however, (perhaps
it's related to the harmonics of the suspension under load, too, or the
dynamics of tire deformation) the noise was present. It had probably always
been there but for whatever reason only was amplified enough at that point
along the drive.

My point is, that as the road surface varies so too should "tire" noise, if
that is in fact what you've got. Do some experimentation and see for
yourself.

 

[JD]

I know that with the tires and the lack of soundproofing I should
expect a reasonable bit of noise from my 2004 STi, and indeed it
seems comparable to other performance cars so I'm not worried, but
I'm curious about what it is that actually makes the sounds.

Two obvious ones are: there's one periodic sound whose frequency is
clearly proportional to the wheel speed, and I wonder if its frequency
is indeed exactly the wheel rpm. I heard just the same in an Infiniti
G35 I borrowed recently. I'd thought it was from the tires, but now
I'm thinking, shouldn't the tire noise be uniform instead of having a
periodicity? So what would be making the periodic sound?

Mine has always done that with the RE 070s on. It doesn't happen with the
winter tires (they have a softer sidewall). It sounds like a harmonic and
it only seems to happen to me when the road surface is particularly smooth
and doesn't change much. It is reaslly pronounced on concrete.

Also, there's a clear hum when I'm cruising at maybe 75mph or so, that
I only get in a narrow speed range, as if something's being vibrated
at its resonant frequency. Any idea what that might be?

There is a hum which seems to be a combination of the turbo and some of the
gearing noise. I get it at about 125 KPH (I'm in Canada) which as around 75
or 80 MPH. That one is more noticeable with the winter tires on (they are
actually quieter than the RE 070s).

I don't mind the noise at all - I expect a bit of noise from the STi,
as it's optimized for performance, not quietness - I just found myself
getting to wondering where the noises actually come from, when I was
driving into work this morning, and I realised I didn't know the
answers and probably you guys do.

-- Mark

There are all sorts of weird noises coming from the thing every now and
again. Because I had never driven anything like the STi, it used to concern
me when I first got it. Now, as long as the noises don't change much and
the thing still goes like hell, I am a happy camper. It does and I am still
a happy camper.

 

[Mark Carroll]

Do any of those noises vary with terrain?

No, the periodic speed-related one and the high-speed hum don't seem
to - at least, they don't vary on regular paved roads, which are the
only roads on which I drive the car at any speed. There is another
sort of noise, which tends to sound like combinations of white noise,
which varies markedly based on the type and quality of the road
paving: I'd assumed that was a louder version of the tire noise I'm
used to in more normal cars.

I moved recently and noticed a strange sound on the drive home. A "hum" at
62-66 MPH -- no more, no less -- on a newly paved blacktop surface over a
long causeway. I really freaked until I realized that, for whatever reason,
it only occurred right on that 3 mile stretch of road at those specific
speeds. I let off the clutch and it went away making me think it was

That is interesting - it does sound related to my 75mph high-speed hum
- it's probably pretty much the same thing! The hum I mentioned also
only occurs within a narrow speed range.

tranny; turns out that if the car was slowing through those speeds that the
noise wasn't present, during acceleration of stead pace, however, (perhaps
it's related to the harmonics of the suspension under load, too, or the
dynamics of tire deformation) the noise was present. It had probably always

(snip)

Interesting - I'll give that a try! (-: Thanks for the great description.

(snip)

My point is, that as the road surface varies so too should "tire" noise, if
that is in fact what you've got. Do some experimentation and see for
yourself.

(snip)

Mmmm. I'll be interested to see what changes when I switch to winter
tires in a few months.

-- Mark

 

[Mark Carroll]

Mine has always done that with the RE 070s on. It doesn't happen with the
winter tires (they have a softer sidewall). It sounds like a harmonic and
it only seems to happen to me when the road surface is particularly smooth
and doesn't change much. It is reaslly pronounced on concrete.

How very interesting - thanks! The G35 I borrowed also had some kind
of Bridgestone tire on large wheels, I think. Let's see how the winter
tires go for me, then. (-:

(snip)

There is a hum which seems to be a combination of the turbo and some of the
gearing noise. I get it at about 125 KPH (I'm in Canada) which as around 75
or 80 MPH. That one is more noticeable with the winter tires on (they are
actually quieter than the RE 070s).

That's also very interesting, and would fit with what the other guy wrote.
I appreciate the information.

(snip)

There are all sorts of weird noises coming from the thing every now and
again. Because I had never driven anything like the STi, it used to concern
me when I first got it. Now, as long as the noises don't change much and
the thing still goes like hell, I am a happy camper. It does and I am still
a happy camper.

Yes, me too. (-: The STi's certainly at a sweet spot in the
performance/price tradeoff I think. As well as going like hell, it
corners and brakes well too - I'm very happy to have a car that seems
to have all-round excellent performance.

-- Mark

 

[Mark Carroll]

That's also very interesting, and would fit with what the other guy wrote.

(snip)

The hum in mine doesn't seem to be changed if I don't throttle, if I
put it out of gear, etc. Still, it's no worry to me, at least.

-- Mark

 

[k. ote]

Mine has always done that with the RE 070s on. It doesn't happen with the
winter tires (they have a softer sidewall). It sounds like a harmonic and
it only seems to happen to me when the road surface is particularly smooth
and doesn't change much. It is reaslly pronounced on concrete.

So has mine. My winter tires are Pirelli PZero Nero M+S, and the noise is
much less pronounced (but not gone.)

Something that cropped up lately was a clunk coming from the rear right
trunk area. I read online that it was the top of the rear-right strut
banging around. It was odd: I'd be screwing around downshifting going down
a hill and right at the end of the stop, I'd be completely stopped, it'd
pause for a moment, then the rear end would settle down almost
imperceptibly with an annoying clunk. It was really getting obnoxious for a
while, and then suddenly--it was gone. All better. No clunk. Fixed itself
basically.

Cool. No more Chinese water torture.

There is a hum which seems to be a combination of the turbo and some of
the gearing noise. I get it at about 125 KPH (I'm in Canada) which as
around 75 or 80 MPH. That one is more noticeable with the winter tires on
(they are actually quieter than the RE 070s).

I think you mentioned before, but what's your winter tire again?

There are all sorts of weird noises coming from the thing every now and
again. Because I had never driven anything like the STi, it used to
concern me when I first got it. Now, as long as the noises don't change
much and the thing still goes like hell, I am a happy camper. It does and
I am still a happy camper.

Same!

 

[CompUser]

Something that cropped up lately was a clunk coming from the rear right
trunk area. I read online that it was the top of the rear-right strut
banging around. It was odd: I'd be screwing around downshifting going down
a hill and right at the end of the stop, I'd be completely stopped, it'd
pause for a moment, then the rear end would settle down almost
imperceptibly with an annoying clunk. It was really getting obnoxious for a
while, and then suddenly--it was gone. All better. No clunk. Fixed itself
basically.

That seems real common on the MY04 STi's...seen a
lot of it over on NASIOC, US dealers will replace
the struts under warranty. Not sure if the
replacements start after a fashion as well...

 

[JD]

So has mine. My winter tires are Pirelli PZero Nero M+S, and the noise is
much less pronounced (but not gone.)

Something that cropped up lately was a clunk coming from the rear right
trunk area. I read online that it was the top of the rear-right strut
banging around. It was odd: I'd be screwing around downshifting going down
a hill and right at the end of the stop, I'd be completely stopped, it'd
pause for a moment, then the rear end would settle down almost
imperceptibly with an annoying clunk. It was really getting obnoxious for
a
while, and then suddenly--it was gone. All better. No clunk. Fixed itself
basically.

I had that. Subaru replaced the rear struts at no charge. Apparently it is
a know issue with the STi. The car handles so well that you don't notice
the difference; only the sound. But once they replace the struts, it is a
HUGE difference in the handling.

 

[k. ote]

I had that. Subaru replaced the rear struts at no charge. Apparently it
is a know issue with the STi. The car handles so well that you don't
notice the difference; only the sound. But once they replace the struts,
it is a HUGE difference in the handling.

Really? That's interesting. Well now I'm going to have to push my dealer for
a replacement. The noise may be gone, but the weird little jerky movements
at the end of a stop are still there, and given how closely I pay attention
to the car, I'm fairly certain the movements weren't there before.

So what's the difference before/after? Are they just new struts, or are they
completely different? Is the rear-end tighter, or is it more/less oversteer
post-replacement?

 

[JD]

Really? That's interesting. Well now I'm going to have to push my dealer
for
a replacement. The noise may be gone, but the weird little jerky movements
at the end of a stop are still there, and given how closely I pay
attention
to the car, I'm fairly certain the movements weren't there before.

I didn't even know they were shot; the dealer just told me my struts were
in. I responded, "What struts?"

Anyway, it turns out that the infamous STi clunk was a bad batch of struts
that came with some of the cars. They replaced them with OEM equipment; just
not faulty ones.

So what's the difference before/after? Are they just new struts, or are
they
completely different? Is the rear-end tighter, or is it more/less
oversteer
post-replacement?

Differences:

There is less understeer going into the corner and the ass-end sits a little
higher. It also doesn't squat as much under hard acceleration and there is
less oversteer on corner exits. You can carry more speed through a turn and
the wheels stay planted better. It just handles better. Also the AFSR
(Auditory Female Speed Restrictor) doesn't get chipped teeth from yapping
about the speed any more. Her uterances are now crystal clear; there is a
downside to everything I guess...