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Old 10-25-2000, 01:57 PM   #1
beachbum
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Member#: 457
Join Date: Oct 1999
Chapter/Region: MWSOC
Vehicle:
---- Smells like
weed and rampage

Thumbs up Anybody take dB readings inside their Impreza?

I borrowed the sound level meter from work the other day and took some readings. Two things to keep in mind. One, my Impreza is farily well sound proofed with a high tech Dynamat substitute (it's more of a putty like stuff, adhesive on one side with thick foil on the front). The only sound influencing modification is the removal of my intake silencer. Two, the meter wants to jump back and forth between its high and low scales at ~70 dB, so these readings may need to be taken with a grain of salt. Here's what I got under varying conditions:
    [*]60 MPH- 65.5 dBA[*]80 MPH- 72 dBA[*]Idle- 42 dBA[*]1st gear max- 83.5 dBA[/list]What do you think? Sound realistic?

    ------------
    Josh Beach
    World's Slowest Impreza Project
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Old 10-25-2000, 02:24 PM   #2
RidinLow
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Member#: 329
Join Date: Sep 1999
Chapter/Region: Tri-State
Location: NJ
Vehicle:
1995 325i
Arctic Gray

Post

The 60 & 80 mph readings will be heavily affected by your tires and the type of road surface they're traveling on. Were the 1st gear max readings taken at WOT?

I will try to borrow a SPL meter tomorrow to compare findings.
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Old 10-25-2000, 06:59 PM   #3
richeich
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Member#: 1353
Join Date: Apr 2000
Vehicle:
2001 Impreza 2.5RS
Silver

Question

Where'd you have the meter situated? I can borrow one also, but I've got a Legacy GT.

Rich
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Old 10-25-2000, 08:23 PM   #4
SkToBe
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Member#: 1278
Join Date: Apr 2000
Chapter/Region: MAIC
Location: Manassas, VA
Vehicle:
2001 RS
Aspen White

Wink

WHAT?! Couldn't hear what you said. Wait a minute, let me turn the stereo down...

All I can hear now is a constant ringing sound.
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Old 10-25-2000, 08:55 PM   #5
zzyzx
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Member#: 815
Join Date: Jan 2000
Location: Florida
Vehicle:
2013 Boss 302 White
2008 S2000 CR ABP

Post

Lot's of things will affect the dB readings. I just installed STi engine and tranny mounts and wow the NVH levels are high! Sounds like a totally (read louder) different car inside.

It would be really handy to have some measurements with mods quoted so that people can understand the differance that different mods have on NVH.

- Steve


[This message has been edited by zzyzx (edited October 25, 2000).]
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Old 10-26-2000, 05:21 PM   #6
RidinLow
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Member#: 329
Join Date: Sep 1999
Chapter/Region: Tri-State
Location: NJ
Vehicle:
1995 325i
Arctic Gray

Smile

Took some readings today.

Car:
MY00 2.5RS sedan
JC intake
Borla/RalliSpec catback
no backseat, no trunk liner, no center console, exposed shifter, removed sound deadening from around the tranny tunnel, halfway worn Yokohama Nexus, windows up

In cabin (measured from passenger seat, facing forward):
60 MPH: 74 dBA
1st gear max: 95 dBA

CA 3000-5000 RPM Noise Pollution Test, measured 20" from behind muffler:
95dBA @ 5000 RPM (just passing!)

At redline, 20" behind muffler: 105 dBA

Although the outside readings were taken when the car was warm, it wasn't quite "hot" enough to make the muffler as loud as it can get on a hot day after running for a while. So things could be louder.


[This message has been edited by RidinLow (edited October 26, 2000).]
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Old 10-26-2000, 05:23 PM   #7
RidinLow
Scooby Guru
 
Member#: 329
Join Date: Sep 1999
Chapter/Region: Tri-State
Location: NJ
Vehicle:
1995 325i
Arctic Gray

Smile

As a point of reference:

200 ft from a jet taking off: 125 dBA
20 ft from a subway train: 90 dBA
1 ft away from a talking person: 70 dBA
5 ft away from a soft whisper: 30 dBA

An increase of 10dB represents a 10 fold increase in sound power and a 100 fold increase in sound pressure. Doubling the sound power will raise the sound pressure levels by 3dB.

[This message has been edited by RidinLow (edited October 26, 2000).]
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Old 10-26-2000, 07:47 PM   #8
beachbum
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Member#: 457
Join Date: Oct 1999
Chapter/Region: MWSOC
Vehicle:
---- Smells like
weed and rampage

Post

Hey, guys, I've been away from the computer all day, so I just got a chance to reply here. Let's see... I've got Pirelli P7000SS tires, and I measured this on fairly worn asphalt. The meter was held in a comfortable position, with the mic about halfway between the shifter and the rearview mirror. The meter I used has a max hold setting, so I set that and ran to redline in 1st gear.

I spend ~350 miles a week in my car, so having a fairly quiet car is kinda nice. For no more weight than this added (15 pounds, max), I think it was really worth it.

P.S. I won't even post what my stereo hit. It's embarassing considering all the work I put into it... Good thing I didn't build it for SPL.

------------
Josh Beach
World's Slowest Impreza Project
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