I've never seen any numbers for the ambient SPL in the tC with or without sound deadening so I've decided to find out. I purchased a Galaxy Audio Sound Pressure Meter from American Musical Supply Here and 40 sqft of Damplifier. I've measured the ambient SPL in the tC (A Weighting) and at idle it is about 54 dB with the rear seats folded flat. On the highway at about 70mph (also with the seats folded flat) it hovers around 57dB to 60dB. Once I install the Damplifier (in the doors only) I will do the same measurements. I'm waiting on my new speakers to come in before I tear into the door.

 

Honestly, you'll move down about 3~6dB, but it depends on where you have the sensor and where it's pointing.

I made the mistake of having the sensor in the front pointing up.

While I lowered the noise floor very noticably over stock...because the sensor was pointing at the now noisest part of the car, the roof, it was totally invalidated

 

SPL meters aren't really the best way to judge the effectiveness of damping material. If you perform tests using an RTA, you can see how much of a difference it makes at various frequencies, as it'll have an effect on some ranges more than others. Also, most such SPL meters aren't very accurate at very low or high frequencies, they're more for checking average SPL in the 100Hz to 10kHz range, and you can't put much emphasis on their readings above or below that. For some meters, people have done testing to determine how many dB you should add or subtract when using them to determine SPL at various frequencies (using test tones) so you can plot a more accurate response (for those that don't have access to an RTA), and you might be able to find such on the web for you specific meter.

Damping will be most effective at reducing road noise, which happens to be centered around 30Hz in a lot of vehicles, but it's also somewhat dependent on road surface (drive around with an RTA connected and you can see for yourself). This is one reason why subs are often more important in the car than home, and why their output level is set higher than the mids & highs, as you have to overcome the noise floor produced by road noise, in order to acheive adquate dynamic range in the bass region. Right where the damping will have the most effect and do the most good, is where your meter is least accurate.

Just thought you might want to know.

 

Downside to getting a GOOD RTA in a car...I tried this with the Term-Lab RTA and it pretty much sucked...but it worked on a laptop.

We had it deadened though before we got our LMS...If I could hook that up in car, I bet I could get some bad ___ curves.

Of course, I could just barrage the car from outside before and after dampening in the shop....

We'll do that one of these days.

 

Well the main reason I got the meter was to compare my Type-Ss to SLC265s I have coming in. But I'm also doing this because while not the most scientific method it will at least give me an idea. Eventually I plan on getting much denser dampening and I'll redo the test then. Good to know about the directioning though. I had the meter right in front of my face, because that's where it matters how loud it is.

 

^ Sure, SPL meters are fun and can be helpful when used appropriately. People shouldn't be too concerned about my earlier post, most people aren't really interested to the extent that info would matter, it was mainly intended for the fanatic audiophile and SQ competition types, who should already be well versed in such areas.

 

So...you don't think people would care if I RTA'd the car from the outside and played a 20~20kHz sweep, then deadened it and redid the sweep?

Term-Lab RTA sucked too hard, but now that we have LMS software...much better RTA

 

so what kind of sound deadener would be best? Im trying to cut down on road noise and a loud muffler and right now im back to a stock exhaust cause i wanted to install some deadeners, but would like to know what is best with good $ to deadening ratio. Thanks.

 

Well, of course some people would care. You know what I mean, most people don't even RTA their car or really tune their systems at all, as long as they have the amount of 'boom' they want and it sounds clean to them, they're happy.

However, you should certainly go ahead and proceed with your tests. Any improvments that you measure and document can be used in your marketing material to entice people to buy your product. Showing the approximate improvements on an RTA graph will make it easy for people to see and understand.

Please be sure to show your results at idle and while driving, as people will be able to see just how much road noise there is with the latter. If they're able to reduce the SPL in that range with damping, then they could lower the amplitude of their subs (compared to w/o damping) and improve perceived SQ at the same time. Ya, as if anyone would turn down their sub gain.

 

I was being mostly sarcastic knowing that someone like you or I would like to see the results.

I need to get another car that isn't deadened since the xB is deadened all to hell now.

 

Also worth mentioning when I redid my measurements the SPL at idle was more like 45dB which makes more sense to me than the previous number. It wasn't the direction I pointed the meter I think my engine was running at 2k RPMs in morning since it was a little cold.

 

Read up:
Sound Deadener Showdown
Car Audio.com
Sound Domain Forums
ICIX Sound

First link will probably be most useful.

 

Sorry I didn't pick up on that, I'm far too serious about audio to detect sarcasm, as you can tell. :D