2nd Gen Non-Engine/Transmission Measured '02 noise levels...

[Pit Bull]

Thanks illflem, very interesting. What I think is interesting is that my Truck is not that loud driving down the road. No problem talking or holding a conversation. I don't run along the side of the truck when it is going down the road so the noise it makes does not concern me. I also don't eat at fast food resturants where I would have a problem ordering at a drive through. The chart indicates using the "A" range and Gary indicated that his reading on the interior were in the 60's using the "A" range which is quiet. I guess I don't see the noise problem at least I don't have one. Of course I like Harley and the way they sound. :-{} :-laf

 

[Lsfarm]

A range vs C range

Hi Pit Bull, actually Gary posted using the C range. His interior is in the 75Db range at idle, 83 or so when going down the road at 50 Mph.



Even my rig with lots of noise insulation is not in the 60's in the C range.



This is the first posting of any A range readings on this thread: [that I've read], my truck idles at about 57-58Db on the A range. Low to mid 70's on the road.



C range: 75 Db is pretty loud, and 83 is certainly not quiet. The heater fan on high and on vent is 78Db, and it is annoying to try to carry on a converstion over that noise, at least for me.



We have to remember that everyone is different, I remember enjoying ear shattering rock music, and could actually carry on a conversation while 'listening' to 'music' at those volumes. Luckly my hearing survived that abuse, or else I couldn't hold the job I have.



So what isonly noisy for one person is just plain loud and obnoxious for others.



Somehow I think this is related to age, but I don't want to try to correlate who likes their CTD loud vs the ones who like them queter. and cross reference this to their age.



I know that in a stock uninsulated truck that I have to raise my voice to be heard for a 'normal' conversation. [My voice really carries too!] And others have to speak up for me to hear them. BTW: I take a very sophisticated hearing test every six months, and I have very good hearing, even for a young person, [which I not any more. ]



Interesting thread,



Greg L The Noise Nazi

 

[illflem]

Do Db readings take into account the frequency of the noise?

Personally I can do without the high pitched ones while low pitched doesn't bother me.

Still haven't figured out how anyone would think removing the silencer ring is cool.

 

[Lsfarm]

Sound Pressure

From what I've read, the Db readings are all frequencies. The meter is described as a 'Sound pressure Meter' calibrated in Db.



I sure there are sophisticated meters that can filter out readings for certain frequencies, but my Radio Shack meter doesn't have that feature.



I have to agree, I can't understand wanting to hear more turbo whistle than there already is. But I do like dogs, so I guess if my truck whistled more, maybe it could be a 'Pied Piper' for the neighborhood dogs to follow??

 

[Pit Bull]

Originally posted by Gary - KJ6Q



Also worth noting are meter ranges and settings used -

using a more "generous" range "A" showed NO DB level at all for ambient noise, since the frequency response for that range is limited, and dropped the interior noise level of my idling truck down to an indicated 62 DB -

LS, this is what I was quoting from Gary. When I went to the "A" range chart that illflem provided it did not look that bad for the inside of our truck. I think you are right about hearing. I have had my hearing tested recently and I have above average hearing. I never went to rock concerts, much, and if I did go I would stuff some paper in my ears to filter out some of the sound. No getting around the fact that our trucks are loud. But like I said mine doesn't bother me, even on a 3-4 hour drive. I drove from KCMO to LA once in a Corvette with side pipes. Had to wear ear plugs because of the constant drone.

 

[Gary - K7GLD]

According to setting info that came with my meter, the "weighting", "A" or "C" scales relates to the frequency response used to determine readings - the "C" scale I displayed above samples all frequencies from32 to 10,000 hz - the "A" scale arbitrarily limits frequency response to 500 to 10,000 hz - eliminating measurement of those frequencies BELOW 500 hz. Since LOTS of the sound levels generated by the Cummins fall into that lower hz range, LIMITING those frequencies tend to artificially "tilt" DB readings away from reality.



As an example, I carefully re-sampled my own truck, and readings with the "A" scale, show inside readings at idle, stopped, at 61 DB - coasting at 50 mph gave 65 DB, which did not change when under power - probably because the noise level increase previously displayed on the wider response "C" scale was now not being indicated on the "A" scale - but it WAS still there!



Same with the outside readings - where there WAS a 2 DB difference in readings from right-to-left side on the "C" scale, they are both the same at 82 DB on the "A" scale - again, probably because the increased noise level is in the lower frequency range the "A" scale ignores...



I just think the "C" scale is more a accurate indication of reality in readings of this type, since it register a wider range of sound - not an artificially limited amount.

 

[Boldt's Wagon]

Here are some year old sould level observations:



http://216.235.147.117/forums/showthread.php?s=&threadid=33048&highlight=radio+shack+drone

 

[Jumbo Jet]

Very good information Gary.



My truck sounds louder (after reaching operating temp) since the last oil change. The dealer put in 10w30 since it is 'winter'. Just seems like it is louder than with the Rotella 15w40.



Any one have any information relative to oil weight and temperature?

 

[Lsfarm]

I need to read the manual

I guess I need to find and read the manual for my Db meter again. I remember that the A scale was supposed to simulate our human hearing closer than the C scale, but I didn't remember the frequency clipping on the top and lower end of the scale.



Pit Bull, I also forgot that Gary mentioned the A scale in the text of his message, I only looked at his table of readings.



Seems like I have a case of CRS: Can't Remember S**t .



I had a '68 corvette convertible with sidepipes, it was absolutely obnoxious, and that was years ago when I did go to rock concerts.



Yet another noise reduction: I took some extra foam and rolled it up like a small sleeping bag and stuffed it behind the windshield wiper motor last friday, and this morning when I started the truck in the airport parking lot with ambient temp of 8*, there was a noticeable drop in the amount of noise coming through the defrosters, and from directly in front of the driver. One TDR member filled this cavity under the windshield with spray-in expanding foam.



Greg L. The Noise Nazi

 

[Gary - K7GLD]

JJ - in regards to temperature, and its effect on sound levels - I haven't done a detailed test, but DID see noise levels drop a rather quick 3 DB on the "C" scale - probably woulda still done it in the "C" scale, since most of the cold engine noise seems to be the higher-pitched clicks and clacks that disappear as the engine warms up...

 

[KL]

I am going to see the Rolling Stones tomorrow night (haven't been to a big rock concert in many many years). I wonder how many Db that will be? After that I will probably think my truck is real quite for a few days. When I get some free time, I have some more GSI foam to put on. Its a closed cell type with a heavy barrier (same weight as the 1/2 inch Sound Stop Foam), but its called "GSI Sound Stop Carpet Underlayment". Anyone try something like this? KL

 

[Dave Zuber]

Hey Gary, Thanks for the post. I just bought some lead sheeting for my engine's sump and I'm starting a sound-abatement program. My goal is to quiet the truck down enough that a new 4" exhaust won't be noticed by the wife (too much).



I'd like to suggest you change or re-check some of your tests, mainly the ones where you lay the sound meter on a hard surface. My Analog Radidio Shack sound meter will read much higher sound when laying on a vibrating hard surface like the fuse box. Also, when it is setting on a hard surface that will reflect the sound, like your kitchen chair. Even when you hold it close to your body it will read higher or sometimes lower by 2-3 db. Laying it on the seat or arm rest seems to make no differance.



I'd suggest laying it in your hand a few feet from your body. This should make the readings more accurate.

 

[Gary - K7GLD]

Good suggestion Dave - thanks - but to tell the truth, my goal wasn't so much to establish ANYTHING like a scientific or lab test - only a basic one that is easily duplicated by anyone with access to a decent DB meter - that's why I also posted a view of my setup, to demonstrate EXACTLY how my tests were done in case someone DOES want to duplicate it...



That's ALSO why I only took readings with the truck idling at a standstill, and under relatively reserved in-motion scenarios - the standing still example is the SAME one used in the TDR magazine, issue 38, page 49, other than the fact they used the meter's "A" scale - the one measurement *I* added in motion is one easily duplicated by anyone. Sure, I coulda included some hill climbimg tests too - IF I wanted to really get involved - I didn't!



Besides, what percentage grade would I use? what speed? what gear and RPM - and how would guys with Auto trannies duplicate that? Should I tow a load? How heavy? And more to the point of how much VALUE would those additional measurements BE to others who COULD NOT duplicate them exactly?



I really think that as long as a person is careful to use the SAME test methods in before/after testing or in making direct comparisons with someone else, it's probably not terribly critical - and when you start muddying the water with all sorts of additional, difficult to duplicate tests, you start defeating your purpose - besides *I* would think that any testing and subsequent noise reduction that provides measurable benefit in ANY chosen method - standing still at an idle - in moderate motion, etc. , will ALSO generally provide the same approximate noise reduction all across the varied normal use of the vehicle.



Most CAN easily duplicate the ones I did provide - and THAT was my goal.