How noisy is your TJ really?

Tigerman

Tigerman

TJ Enthusiast
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North Hills, CA
Hi all,

I took some noise level readings while driving the Jeep to see what contributed the most and least to the noise level. Would you be able to do the same so we can quantify and compare?

Test vehicle: 1998 4.0 TJ with full doors and factory hard top.

Phone: Samsung S8

1. 70 mph, freeway, under power: 74/75 dB
Screenshot_20181103-225250_Sound Meter.jpg
2. 70 mph freeway, coasting in neutral:
69 dB
Screenshot_20181103-230150_Sound Meter.jpg
I am deducing that engine under power adds extra 5dB.
3. 35 mph on the street: 70dB
Screenshot_20181103-230654_Sound Meter.jpg
Wind noise from going 35 mph vs 70 mph 4, 5 dB.
4. Stopped, idle: 60 dB.
Screenshot_20181103-230543_Sound Meter.jpg

5. Engine off: 39 dB
Screenshot_20181103-230744_Sound Meter.jpg
Wow, the largest contributor in my configuration is the motor!!! Not the wind. It adds 20 dB.

Conclusions:
Motor sound is the largest contributor at 20dB.
Idle motor vs under normal power +5dB
Wind noise increases liniearly and at +10dB at 70 mph calculates to +0.14dB/mi.

Your biggest concern is the motor so engine compartment and firewall sound proofing should have the largest impact.

What are your numbers?
 
Last edited:
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I'll have to give it a shot too. My soft top adds quite a bit as I have a couple broken straps that keep it from being taught
 
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Awesome idea for a thread! Whenever I get my TJ back I'll have to test this out. I've always suspected a large amount of the noise was coming from the engine itself. It would be nice if someone made some sort of underhood installation. Maybe pair that with some sound deadening material on the firewall itself. I'll bet you could reduce some of the noise drastically!
 
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I’ll have to try this out next time I have a passenger along.


I think the wind noise can depend on the outside conditions and the state of your seals. When I had my Tj that wind noise was loud hah.
 
Tires for me, when I went from my old MTZ's to my Trepadors the added noise from a couple hour trip with the door windows out had my ears ringing like a rock concert when I shut down.

—
There must have been a time
when we could have said no.
 
I was going to test this out today but we have a wind advisory going on so I think I’ll wait until that factor is more neutral.
I have an I phone and don’t see your same app but downloaded dB meter. I’ll see if that contains the same sort of measurements as yours.
 
To try to be consistent, though we will all have different phones/apps/amount of lint in the microphone - where approximately was the phone in your TJ as you tested?
 
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rasband said:
To try to be consistent, though we will all have different phones/apps/amount of lint in the microphone - where approximately was the phone in your TJ as you tested?
Click to expand...

The phone was mounted on the dashboard on a magnetic holder and you are absolutely right. The device used, the pavement condition, traffic conditions, everything will make a difference.

For best results it is better if we pay attention to the difference of numbers in your own vehicle with your setup rather than the difference between our numbers. That way the same conditions apply and you will be able to tell what exactly produces the most noise. Freeway vs street gives you wind noise difference. Engine off vs engine on gives you pure engine noise difference, etc...

I am very happy some of you decided to test this out. We can gather somewhat scientific data and get a good idea from this what works and what doesn't.

Cheers :)
 
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I'm driving around this morning and trying the app out.

Engine off 49-51db.
60db parked at idle.
78db at 3000rpm parked in neutral.

Today I have the hard doors with the windows rolled up. Some highway driving at 60mph. No rear windows. I haven't seen anything louder than 78db.
 
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06 LJR 6spd, OEM other than a RallyTop hard top with Wrangler MT/Rs:
  • Engine Off: average 34
  • Engine Idle: average 60
  • 35mph: average 75
 
jjvw said:
I'm driving around this morning and trying the app out.

Engine off 49-51db.
60db parked at idle.
78db at 3000rpm parked in neutral.

Today I have the hard doors with the windows rolled up. Some highway driving at 60mph. No rear windows. I haven't seen anything louder than 78db.
Click to expand...
rasband said:
06 LJR 6spd, OEM other than a RallyTop hard top with Wrangler MT/Rs:
  • Engine Off: average 34
  • Engine Idle: average 60
  • 35mph: average 75
Click to expand...

Looks like the results are very similar with the engine being the number one contributor. :) cant wait to get some soft top half door data.
 
Tested mine this morning. Air/heater off.

46 with engine off.
63 at idle.
73 at 40 mph
82 at 70 mph.
 
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tworley said:
Bestop soft top. Not the twill version
Click to expand...
I was wondering why your numbers were around 8 to 10 dB higher. Awesome data :) The great thing is that the differences between your own readings are very consistent and inline with the rest of the sample data. The question I have is where exactly the sound getting through to the cabin? The firewall and the floor in the front or primarily through the rear passenger wheel well and the muffler?
 
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