How noisy is your TJ really?

Yesterday I put the hardtop back on my TJ for the winter. I did noise testing as well, using the NIOSH SLM tool on my iPhone, with my phone held between the two seats at my ear level. Readings are taken within 2 hours of each other between 12 noon and 2 pm, ambient temperature was 43 degrees fahrenheit, winds WSW at 10-15mph, mostly sunny, and when moving I was moving East to West on both readings on mostly or nearly level Virginia highway asphalt with readings started/stopped from the same point on the highway. My tires and suspension are stock height. HVAC controls were on lowest fan setting and middle of the temp scale for heat, with airflow set to the footwell. My soft top is a Quadratop by Quadratec, and it's pretty low quality. Hard top is OEM as delivered from the factory with no additional insulation or soundproofing. I am using NOICO on the floors of the tub and the ACC carpet is using the heaviest mass backing I could purchase. Full hard doors. Here are the results.

Soft top:
Idle: 46.1 db
65mph in 5th gear: 85.5 db
65 mph in 5th gear with a heavy winter glove over the shift knob: 84.5 db

Hard top:
Idle: 46.1 db
65mph in 5th gear: 76.9 db
65 mph in 5th gear with same glove over the shift knob: 75.9 db.
 
anarce said:
First of all, apps on phones can be wildly inconsistent...
Click to expand...

I found this thread and was floored by the low decibel readings that people reported. I had installed the first app that came up on the iPhone App Store when searching for “Decibel” and was getting normal highway readings like this:

1614214582469.png


which made me very worried for my hearing! Then I saw how quiet others reported here and figured something must be wrong.

I installed the NIOSH SLM app mentioned here and was relieved to find it more consistent. The below screenshot was taken just second after the one above:

1614214699974.png


I didn’t find much difference in results under power or coasting, maybe 1db.

Here are my numbers:

Idle 51db
40mph 63db
60mph 68db
65mph 68db
70mph 71.5db
75mph 74db
80mph 73db

hard top on
full doors
windows rolled up

Phone held at ear level between two front seats

some sound deadening installed - floor and doors (not firewall), and hard top boom mat

edit to add:
4.0L
Sport
31” tires (destination x/t)
~1” H&R lift
4.56 gears
 
Last edited:
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All my results are an average of 20 seconds of recording w/ NIOSH app
Car off - 29.5
Idle - 44.6
50 MPH - 65.3
65 MPH - 68.5
70 MPH - 70.5

Car is fully sound deadened (including doors and partially the firewall) with bedlinered hardtop, full doors, 31” Wrangler MT’s, 2.5” lift
 
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