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presslab
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Joined: September 29, 2008
Posts: 1730
Location: Sonoma County
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 Posted: Mon Oct 29, 2012 8:04 am Post subject: |
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| snowsyncro wrote: |
| Re the weighting, sure 'A' weighting will better quantify the subjective effect on us humans, but as an engineer I always want to see flat weightings -- I can do my own weighting if I want. |
Sorry to beat a dead horse here... But without using the A weighting the whole "10 dB is twice as loud" goes out the window. The human ear is the thing you're trying to please, so if your measuring device has a different response then you don't really have a feel for the real change in volume.
Here's a chart showing the difference in weighting. Linear would be a straight line at 0 dB.
You can see that at 100 hz, A weighting is 20 dB down. That's a huge difference. Say for example your square of tar lowered the resonant frequency of the panel from 1000 hz to 200 hz, but kept the linear sound amplitude the same; the linear measurement will show that you didn't improve things. But if you used A weighting it would show you improved it by 10 dB.
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snowsyncro
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Joined: January 11, 2009
Posts: 1557
Location: East Preston, Nova Scotia, Canada
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| Posted: Mon Oct 29, 2012 9:59 am Post subject: |
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| presslab wrote: |
| snowsyncro wrote: |
| Re the weighting, sure 'A' weighting will better quantify the subjective effect on us humans, but as an engineer I always want to see flat weightings -- I can do my own weighting if I want. |
Sorry to beat a dead horse here... But without using the A weighting the whole "10 dB is twice as loud" goes out the window. The human ear is the thing you're trying to please, so if your measuring device has a different response then you don't really have a feel for the real change in volume.
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I may have created some confusion with my comment. Sorry about that. You are absolutely correct about the 'A' weighting, and the reasons for its existence. What I was trying to say was simply that, as an engineer working in the acoustics field, I would always want to collect raw, unfiltered data. I can do the post-analysis filtering myself to suit my needs. For most, who are of course simply interested in the perceived before and after effect, then yes of course the 'A' weighting is the way to go.
RonC |
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denwood
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Joined: July 29, 2012
Posts: 1047
Location: Thunder Bay, Ontario, Canada
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| Posted: Mon Oct 29, 2012 10:15 am Post subject: |
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Important note..remember the FFT analyzer (front seat, line graphs) has no weighting option, and the superimposed plots are so close, i'm suggesting that a person in the front seat would not hear the difference.
Subjectively I'd say this was true. I couldn't say I heard a difference.
Now in the back seat, (RTA, bar graphs) one thing I noted is that the "Overall" db ratings at top left in the graph, are consistently lower after treatment by 3-5 db. What I can't find out is what that number averages, so have sent a querie to the Faber folks on what that represents. Thoughts?
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snowsyncro
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Joined: January 11, 2009
Posts: 1557
Location: East Preston, Nova Scotia, Canada
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| Posted: Mon Oct 29, 2012 10:35 am Post subject: |
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| denwood wrote: |
Important note..remember the FFT analyzer (front seat, line graphs) has no weighting option, and the superimposed plots are so close, i'm suggesting that a person in the front seat would not hear the difference.
Subjectively I'd say this was true. I couldn't say I heard a difference.
Now in the back seat, (RTA, bar graphs) one thing I noted is that the "Overall" db ratings at top left in the graph, are consistently lower after treatment by 3-5 db. What I can't find out is what that number averages, so have sent a querie to the Faber folks on what that represents. Thoughts? |
The Faber folks will have the final say, but the common understanding of an 'Overall' reading of sound level, is the that it is the same as what a proper sound level meter would give if it was giving a single number answer. Typically, this is the summation across the spectrum from 10 Hz to 20 kHz, 'A' weighted. So, wide band sound level.
When you hear the news reports where they say the sound was measured as X dB, and the threshold of hearing damage is 140 dB or whatever, then that is what they are talking about. But of course they never say at what distance the measurement is made...one of my pet peeves.
RonC |
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denwood
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Joined: July 29, 2012
Posts: 1047
Location: Thunder Bay, Ontario, Canada
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| Posted: Mon Oct 29, 2012 11:09 am Post subject: |
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Ran a quick test using the signal generator (pink noise, also white noise) via a 100amp amplifier, and a 5.1 system. Observed 0 and 10db RTA increased volume from the amp using A weight, and the same using Flat weighting. With pink noise, a 10db change read the same regardless of weight..and then I figured out the difference between white and pink noise! Aha.(identical energy across the frequencies..different story.
Snow, you're correct on the overall. It's an average of peak db, irrespective of frequency. So the rear seat tests do show this:
60km/h test 1 before: 72.7db after: 67.7db
60km/h test 2 before: 73.9db after: 70.3db
100km/h test 1 before: 76.0db after: 70.05db
100km/h test 2 before: 75.7db after: 73.82db
The frequency of this drop based on the RTA graphs had to be between 20 and 125hz. So one could conclude that a rear seat passenger would observe 3-5db reduction in noise if they applied dynamat as I did, with the cushion in place. On the db scale, 3db is described as "barely noticeable" and 5db is described as "clearly noticeable". However, at frequencies like 100hz, a 5db change might compare similarly to 10 db at 1000hz.
Press, with respect to this chart on the human ear sensitivities: http://www.audioholics.com/education/acoustics-principles/human-hearing-amplitude-sensitivity-part-1 would it be fair to say that a 5db drop at 100hz (flat weighting) should be very noticeable? I'm roughly mapping it to 10db at 1000hz equivalent. I believe what you're saying is that had I used A-weighting I would have seen an approximate 10db drop on the graph, instead of 5db. Correct?
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denwood
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Joined: July 29, 2012
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Location: Thunder Bay, Ontario, Canada
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| Posted: Tue Oct 30, 2012 8:08 am Post subject: |
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After doing some more research, and a lengthy pm from snowsyncro (thx!), a few more thoughts. I've modified my observations a bit because my tests are clinically correct, however, they don't reflect exactly how the human ear would perceive the change. Presslab's comments are right on the mark.
This also illustrates how very misleading a peak db level (used everywhere in marketing) can be.
1. The human ear is more sensitive to the frequency range corresponding (surprise!) to speech. This just means that high frequencies and low frequencies are not heard at all below certain volumes, and once perceived, we're less sensitive to them.
2. The tests I did reflect the "true" changes. Settings in the software, specifically "A" weighting, would have adjusted the results to better reflect what the human ear would perceive.
So with the knowledge that the peak changes happened in around 100 hz, for rear seat passengers, it's safe to say the difference before / after Dynamat Extreme was barely perceptible in terms of your ears.
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joseph928
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Joined: September 22, 2011
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Location: flagstaff az.
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| Posted: Tue Oct 30, 2012 9:32 am Post subject: |
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Dynamat Sound Deadening Testing Before and After - Worth it?  Yes! We did 90% of our van in Dynamat at Go Westy 5 years ago when we did a rebuild . To me it sounds great, that is less sound, and when friends get in to the van and shut a door and say I wish mine sounded like this! I don't need anymore proof. Poo on all the fancy tests I'm happy and I paid for it and thats all that counts. 
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1987 syncro westy tin top sun roof , GW2.3, rear locker, decoupler, Gary Lee tire rack & winch mount, lift, south african grill, big brakes , rhein alloy ,15 BFG AT, Fiamma 10 foot awning ,140 watt rear 85 watt front solar , mppt, truckfridge, automatic fire extinguishing system, tencent oil cooler, And a RMW SS exhaust! - 1971 bug convertible 1776 engine- 2010 Subaru turbo - 1993 Toyota 4x4 truck - 1999 Harley 95 CI, big bore, Andrews cams . Also 80-84- vans. Stock 65 sunroof bug. |
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JeffRobenolt
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Joined: February 25, 2007
Posts: 1513
Location: Wisconsin
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| Posted: Tue Oct 30, 2012 11:12 am Post subject: |
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| denwood wrote: |
So with the knowledge that the peak changes happened in around 100 hz, for rear seat passengers, it's safe to say the difference before / after Dynamat Extreme was barely perceptible in terms of your ears. |
You only did 2 places that would give you the least return.
I think you need to focus your analyzing and research on what and how to sound deaden instead of doing 2 panels and saying it isn't worth it.
It is a huge project if you are going to do it right.
Jeff
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| jfats808 wrote: |
| Most, some, few is not all. You can always learn something from everyone , even the fool. |
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denwood
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Joined: July 29, 2012
Posts: 1047
Location: Thunder Bay, Ontario, Canada
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| Posted: Tue Oct 30, 2012 12:12 pm Post subject: |
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I agree completely. The goal here was to see if lining the area over the engine and firewall was effective. For the few hundred dollars, without further treatments, it's not. One might assume, that because the engine is sitting in the back, and you've treated the area that is easy to access, and immediately surrounding it, that you'd see a difference. You should draw the conclusion that in order to be effective, you should do the entire vehicle, or target different areas than I did. Now the question is, how effective?
The tests show how the front seats are a fair bit louder than the rear. Therefore tackling wind noise and road noise up front would likely be the starting point, not the back. Ideally before embarking on all the expense and time of sound deadening, you would test both the front and back of your vehicle as I did, and understand where the problem frequencies are, so you can target them effectively. Just testing for overall db levels is not enough IMHO based on what I've learned here.
What this thread needs now is for someone who is doing the complete job to test before and after in a similar manner. That person is not me, as the van is already painted (five years back) and the noise level for me is just fine. Having a starting point (and the plots) of my setup should give someone else a good starting point to compare  If nothing else, I hope it inspires someone to take a similar method, and add to the results. I'm offically offering up any assistance I can manage to help.
Dynamat advertises a 151F degree temp drop (engine bay vs cabin) from a hot rod that is fully treated. http://www.dynamat.com/download/vss/2653_1933_Ford.pdf
The engine bay is 223F, the inside of the car, 72F. There's a 151F difference. Really? What was measured? How? Where were the measurements taken? What was the baseline?..blah, blah, blah. It just drives me craaazy that claims are made (and I'm not saying the results are true or false). However, reporting that there are large differences between the engine bay and cabin temps is stating the obvious.
The important issue Presslab and Snowsyncro have correctly observed/commented in this thread is that with Real Time Analyzer tests, the weighting used is very important, and that a true measured 10db drop at 30hz sounds amazing, but you would not likely notice it. In other words, stating that sound levels dropped Xdb means nothing without two pieces of information. How was it weighted? What frequency did it drop at? For example, at 100hz a 25db tone would sound the same volume, to your ears as a 60db tone at 30hz. The general rule that a 10db increase in noise level is perceived as twice as loud is only applicable to a tone at 1000hz. You've all heard this tone during the typical color bar pattern and tone emitted by a TV station that is off the air.
Google "dynamat sound tests". This thread is number one. It shouldn't be!
Cheers,
Dennis.
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2PLY
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Joined: November 09, 2008
Posts: 46
Location: Maple Valley, WA
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| Posted: Thu Nov 01, 2012 9:35 am Post subject: My Sound test.. sorry, no graphs. How bout a video? |
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I was just directed to this thread so I have not had the chance to read all 3 pages, but I just happened to upload a video a few minutes ago from a test I made last night after installing my version of wall sound / thermal insulation in my 91 Syncro Westy.
I used a no name butyl rubber / aluminum skin sheets from eBay and then added a thin (1/4") thermal insulation that was given to me to try (don't even know what it's called) that has some sort of expanded squishy plastic sandwiched between two thin skins of aluminum foil that I applied with double stick tape.
Then for the final Thermal Insulation to replace the standard fiberglass, I used sheets of 1" thick K-Flex brand of Closed Cell Neoprene, Also applied with double sided tape bought from the same supplier.. So here is the unscientific, no graph knuckle test video...
Link
Not sure if that's the way to add a video URL or not to the Samba.
OOPS! I stand corrected.. accidentally posted THIS thread URL... should work now.. 
Curt
Maple Valley, WA
87 Syncro Westy, 2007 Subaru 2.5L
91 Syncro Westy, Stock Engine... Preparing for 1.9L TDi
Last edited by 2PLY on Thu Nov 01, 2012 10:02 am; edited 1 time in total |
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svenakela
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Joined: July 19, 2006
Posts: 776
Location: Ekerö
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| Posted: Thu Nov 01, 2012 9:58 am Post subject: Re: My Sound test.. sorry, no graphs. How bout a video? |
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| 2PLY wrote: |
[youtube]http://www.thesamba.com/vw/forum/viewtopic.php?t=532900[/youtube]
Not sure if that's the way to add a video URL or not to the Samba
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It's the way, but you're adding a link back to this thread. Not a Youtube link...  |
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ZanaEvyPapa
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Joined: July 31, 2010
Posts: 255
Location: Gainesville, FL
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2PLY
Samba Member
Joined: November 09, 2008
Posts: 46
Location: Maple Valley, WA
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| Posted: Thu Nov 01, 2012 10:04 am Post subject: Re: My Sound test.. sorry, no graphs. How bout a video? |
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| svenakela wrote: |
| 2PLY wrote: |
[youtube]http://www.thesamba.com/vw/forum/viewtopic.php?t=532900[/youtube]
Not sure if that's the way to add a video URL or not to the Samba
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It's the way, but you're adding a link back to this thread. Not a Youtube link... |
Thanks svenakela, it's fixed now but looks like ZanaEvyPapa already found it... Can't get past you guys no matter how bad I F**k it up..
And I might add that my Van is inoperable at the moment so it's far to late to get any "Before" readings.. I was just trying to stop my van from sounding like I was inside a steel drum ... which of course, it is . |
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ZanaEvyPapa
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Joined: July 31, 2010
Posts: 255
Location: Gainesville, FL
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| Posted: Thu Nov 01, 2012 10:12 am Post subject: |
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Thanks 2PLY. Can you dig up the names of the exact products you used?
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denwood
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Joined: July 29, 2012
Posts: 1047
Location: Thunder Bay, Ontario, Canada
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| Posted: Thu Nov 01, 2012 10:33 am Post subject: |
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Joseph228:
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| Poo on all the fancy tests I'm happy and I paid for it and thats all that counts. |
Coffee out my nose on that one . If you're happy...perfect.
2ply, these tests are simple to do, and I would be willing to help all that is required. All you need is an iPhone or ipad and the app. A lot of folks would be interested to see how a fully treated van would sound!! By firing up this thread my hope is that others like you would do tests duplicating my simple method so we could all decide what works best! There is a massive amount of marketing crap floating around. Don't even get me started with ceramic heat insulating products...which categorically don't work as advertised. 3M to their credit, is one company actually advertising ceramic microsphere additives truthfully.
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2PLY
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Joined: November 09, 2008
Posts: 46
Location: Maple Valley, WA
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| Posted: Thu Nov 01, 2012 10:55 am Post subject: |
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| ZanaEvyPapa wrote: |
| Thanks 2PLY. Can you dig up the names of the exact products you used? |
The Butyl Rubber / Aluminum mat is similar to the popular ones everyone is using.. sort of a Generic version called Audio Barrier from eBay. The second layer was given to me to use from Marius that frequents this forum.. I'll have to ask him what it's called. And the final layer is K-Flex. They make various thicknesses, this being the thickest version at 1". It's a closed cell Neoprene sheet at 36"x48".. VERY expensive but I didn't know how much until I placed the order.. A box of 6 sheets (72 square feet) and a 160 foot roll of 1-1/2" wide double stick tape cost me right at $400.. Let's see if I can post a few photos below.
K-Flex Box
Cutting K-Flex
My back hatch showing the first 2 of 3 layers in progress:
And my sliding door part way complete:
I'm not saying this is the best solution. As far as I know, I'm the only person to do this, or at least, I made the decision without knowing any one that has used this stuff.. I'm hoping it works because I SURE DO NOT feel like removing all of the interior out again.
The engine hump on this van already had the VBLOK stuff from Cascade Audio Engineers and as tests on this thread show, I can't tell if it makes much more difference than the bed pad alone does. I'm just trying to stop the TIN CAN sound of the van when driving over rough roads.
I can't add this 1" K-Flex to the front doors, but I'll use the Cascade Audio Engineers version of that Generic Butyl Rubber / Aluminum mat I used in the back and maybe add the stuff that I got from Marius depending upon whether or not there is room and if it can withstand a wet environment.
However, there is room in the headliner area to add the K-Flex and if I ever take off the dash, I'll do something in there too. For now, I'm looking into replacing the front carpet underlayment with some of that neoprene / lead / neoprene VBLOK stuff that is over the engine to see if I can block more road noise up front.
Don't think that I know what I'm doing  I'm just winging it based upon other mistakes I've made in the past. Cheers!  |
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Californio
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Posts: 1305
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| Posted: Thu Nov 01, 2012 12:35 pm Post subject: |
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Being a thrifty sort of guy, I used foil backed roof flashing from Home Depot to do the entire front end. Compared with Dynamat, which I used inside the engine compartment, it isn't as sticky, so you need to use spray adhesive, let dry until tacky, etc.
Enormous difference.
I pulled the radiator and did all the sheet metal in there, the radiator fan housing on both sides, the underside of the front where possible, behind the headlights, inside all doors, removed dash and did every place under there, including the fan housing--etc. Where I could, I also attached used 1/2" carpet pad on top of the flashing, using the same spray adhesive.
Now I notice the noise coming from the headliner area, which I didn't do...
Carpet inside the rear storage box helped as well, as did carpet on all the shelves etc. of the storage areas (Westy.) Anything that might resonate.
Another thing that helped was using Dynamat on the air filter can (Tiico) in the driver side D pillar.
Each step produces a tiny difference. That's about all you can hope for. |
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denwood
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Joined: July 29, 2012
Posts: 1047
Location: Thunder Bay, Ontario, Canada
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| Posted: Thu Nov 01, 2012 2:04 pm Post subject: |
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Just do me a favor and don't use the words "enormous difference"! Post up the data! Pretty Please.
Seriously, 2ply, I'll Paypal you the $$$ for the app That neoprene you used is likely going to do two things.
1. Really warm up your van in cold weather.
2. Insulate from the higher frequencies extremely well.
Panel dampening, followed by 1" of material like this everywhere should have a dramatic effect inside. Just testing with and without the rear mattress tells you how effective that foam is. I can tell you during cold weather sailing (and i don't do it anymore!) that wearing a 3mm neoprene hood (covers the whole head, including ears) has a dramatic effect on hearing. It's like wearing ear plugs.
I'm intensely (note the use of the word "intensely") interested in your results. Sent you a pm.
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2PLY
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Joined: November 09, 2008
Posts: 46
Location: Maple Valley, WA
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| Posted: Thu Nov 01, 2012 3:13 pm Post subject: |
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| denwood wrote: |
Just do me a favor and don't use the words "enormous difference"! Post up the data! Pretty Please.
Seriously, 2ply, I'll Paypal you the $$$ for the app That neoprene you used is likely going to do two things.
1. Really warm up your van in cold weather.
2. Insulate from the higher frequencies extremely well.
Panel dampening, followed by 1" of material like this everywhere should have a dramatic effect inside. Just testing with and without the rear mattress tells you how effective that foam is. I can tell you during cold weather sailing (and i don't do it anymore!) that wearing a 3mm neoprene hood (covers the whole head, including ears) has a dramatic effect on hearing. It's like wearing ear plugs.
I'm intensely (note the use of the word "intensely") interested in your results. Sent you a pm. |
Yes, got the PM and see that you are not West Coast Canada so that answered that question.
Oh, forgot to say.. My phone is an HTC Android (Thunderbolt) Might not be an app for it.
Comparing the 90 Syncro that was wrecked to my minimal insulated 87 Syncro, the 87 is really noisy, but I'm coming to the conclusion that it's more rough road vibrations resonating through the metal like a bell with the Nokian Tires and the stiffer coil-over suspension.
So my little test last night was encouraging. I also noted that the sound of tapping on the insulated body panel was exactly like the sound of tapping on the window above.. no more metallic ring. So that's a good sign and maybe a step in the right direction.
My 87 Dove Blue with my now wrecked White 90 just before my wife killed it. 
And she REALLY Killed it good!! But just a store bought band-aid on her elbow:
Yep, fell asleep and did a forward flip completely airborne at 55 MPH after hitting a culvert in a Farmer's ditch. I saw the whole thing from the rear view mirror in the 87 Syncro. 
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denwood
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Posts: 1047
Location: Thunder Bay, Ontario, Canada
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| Posted: Thu Nov 01, 2012 5:02 pm Post subject: |
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Wow, it was a nice van...
That accident (and witnessing it) sounds just awful..and she walked away with just a scratch!
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Dennis Wood
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