Sound Absorption
06-07-2002, 01:37 PM
#1
Cruisin'
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Sound Absorption
Has anyone tried any of those sound absorbing panels that you glue inside your doors, engine compartment, etc.? Not that you could ever get a Porsche to be real quiet or would want to, but on a long trip or for an intimate conversation a little less of the usual 'passing lane ambiance' would be nice.
They are advertized as sound deadening, noise absorbing, acoustic absorption, etc. panels. Some are already cut to fit and others are snip it yourself. They all need glue and more than a little effort to get located and stuck.
The prime question, of course, is do they work? And to what degree? Are a couple useless? Do I need to apply these to every 'loose' surface?
All opinions appreciated.
-Franklin '79 SC
They are advertized as sound deadening, noise absorbing, acoustic absorption, etc. panels. Some are already cut to fit and others are snip it yourself. They all need glue and more than a little effort to get located and stuck.
The prime question, of course, is do they work? And to what degree? Are a couple useless? Do I need to apply these to every 'loose' surface?
All opinions appreciated.
-Franklin '79 SC
06-07-2002, 01:44 PM
#2
These sound absorption products are (or were - it's been awhile since I was active in aftermarket audio) popular in the aftermarket car audio world.
They reduce the vibrations inherent in a car by deadening the panels with special composite materials. I've sat in a few cars set up for strictly good audio with this material applied everywhere and it really does make a huge difference if done right and a lot of panels in the car are deadened.
Years ago, my brother installed some Dynamat in his Fiero on the rear fire wall (remember those mid engined things?) and it did cut down on some of the clatter from that cheesy motor that was in that vehicle.
These materials are heavy though, so lots of it adds a bit of weight (not the best thing for a sports car).
Good Luck,
Jay
90 964
They reduce the vibrations inherent in a car by deadening the panels with special composite materials. I've sat in a few cars set up for strictly good audio with this material applied everywhere and it really does make a huge difference if done right and a lot of panels in the car are deadened.
Years ago, my brother installed some Dynamat in his Fiero on the rear fire wall (remember those mid engined things?) and it did cut down on some of the clatter from that cheesy motor that was in that vehicle.
These materials are heavy though, so lots of it adds a bit of weight (not the best thing for a sports car).
Good Luck,
Jay
90 964
06-07-2002, 02:59 PM
#3
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Hi,
my father worked in the 60s as a student at Bayer AG on a project to reduce noise on the Porsche 911. As you see, the problem was already known to Porsche by then, but results were not very encouraging and the use of sound absorbing panels was not very effective on the 911. Here some of the reasons:
1. Much of the noise is transmitted directly via suspension and motor mounts to the body.
2. The air cooled engine is noisy by itself.(If I remember well then for certain markets special noise absobing valve covers were used, so you could try those).
3. These panels are more effective on higher frequencies. It is much more difficult to damp the low frequencies.
4. If you like high tech , then you can try anti-noise equipment as offered by bose and some other companies. These systems produce anti-noise that together with the real noise cancels out. While these systems are mostly used in the aircraft industy, you could give it a try on a low flying air-(cooled) plane, couldn't you?.
Bye
my father worked in the 60s as a student at Bayer AG on a project to reduce noise on the Porsche 911. As you see, the problem was already known to Porsche by then, but results were not very encouraging and the use of sound absorbing panels was not very effective on the 911. Here some of the reasons:
1. Much of the noise is transmitted directly via suspension and motor mounts to the body.
2. The air cooled engine is noisy by itself.(If I remember well then for certain markets special noise absobing valve covers were used, so you could try those).
3. These panels are more effective on higher frequencies. It is much more difficult to damp the low frequencies.
4. If you like high tech , then you can try anti-noise equipment as offered by bose and some other companies. These systems produce anti-noise that together with the real noise cancels out. While these systems are mostly used in the aircraft industy, you could give it a try on a low flying air-(cooled) plane, couldn't you?.
Bye
06-07-2002, 03:03 PM
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Hi again,
I have another solution for you:
Buy a modern car like a BMW , Audi or New Beetle and put in a special sound system. I heared of rumors that the car industry is planing to add a sound option to emulate a flat 6 porsche engine for a 4 cylinder car. I keep you informed...
ANDREAS
I have another solution for you:
Buy a modern car like a BMW , Audi or New Beetle and put in a special sound system. I heared of rumors that the car industry is planing to add a sound option to emulate a flat 6 porsche engine for a 4 cylinder car. I keep you informed...
ANDREAS
06-07-2002, 07:27 PM
#5
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from my experience in audio systems (including some automotive work), allow me to belabor the obvious; acoustics is a really complex field of science & engineering...
There are 2 categories of sounds that you must consider - active, direct sources & passive, harmonic resonances, (a consequence of the active). The loudest components are usually the direct ones (drivetrain, road noise, wind). Secondary sources are not as loud, but sometimes more irritating ("that rumble, rattle, etc. is driving me crazy!"). Car bodies have a low resonance freq., say about 30 - 80 hz. Exciting this range will create much more output, kinda like the tuned port of a speaker enclosure. My opinion is that exposure to noise over long periods is a major contributor to driver fatigue (along w/ dehydration & hi/low ambient temps).
A sound pad in the engine compartment is intended to dampen that primary noise - the engine. It doesn't do much of anything for the other active & passive sources (like exhaust note reflecting off the road). To some extent, one can "tune" the ambient noise levels of a 911 to suit one's taste. Some people like a louder exhaust note, regardless of any claimed performance improvements. Others want to quiet all sounds. Others mask it w/ the 1812 Overture @ 110dB.
I have noted that some soundfield management can be performed experimentally & cheaply. One example is as simple as throwing about fluffy bath towels. On the dash it absorbs the reflections off the windshield. Another towel on, over or behind the rear seats has some benefit. I have not performed these tests rigorously (w/ a dB meter), just using my own analog sensors. {note: this is all "Coupe-based", in Cabs it is almost hopeless to attempt acoustic mgmt, however, towels are always handy for other reasons}
Lately, I have been thinking of searching for some ear plugs that heavily attenuate the low freq. (-20db @ below 200 Hz?), yet pass through most sources above 2500 Hz. (so I don't miss sirens). Passive resonances may be addressed w/ acoustic damping material like Dynamat. Applied to bare metal surfaces of the interior, it is not too heavy & will deaden resonance. I have found 3M Rubberized Undercoating to be effective. It can be applied to the interior, under mats & in doors, since it isn't a heavy, smelly tar-rich material.
There are 2 categories of sounds that you must consider - active, direct sources & passive, harmonic resonances, (a consequence of the active). The loudest components are usually the direct ones (drivetrain, road noise, wind). Secondary sources are not as loud, but sometimes more irritating ("that rumble, rattle, etc. is driving me crazy!"). Car bodies have a low resonance freq., say about 30 - 80 hz. Exciting this range will create much more output, kinda like the tuned port of a speaker enclosure. My opinion is that exposure to noise over long periods is a major contributor to driver fatigue (along w/ dehydration & hi/low ambient temps).
A sound pad in the engine compartment is intended to dampen that primary noise - the engine. It doesn't do much of anything for the other active & passive sources (like exhaust note reflecting off the road). To some extent, one can "tune" the ambient noise levels of a 911 to suit one's taste. Some people like a louder exhaust note, regardless of any claimed performance improvements. Others want to quiet all sounds. Others mask it w/ the 1812 Overture @ 110dB.
I have noted that some soundfield management can be performed experimentally & cheaply. One example is as simple as throwing about fluffy bath towels. On the dash it absorbs the reflections off the windshield. Another towel on, over or behind the rear seats has some benefit. I have not performed these tests rigorously (w/ a dB meter), just using my own analog sensors. {note: this is all "Coupe-based", in Cabs it is almost hopeless to attempt acoustic mgmt, however, towels are always handy for other reasons}
Lately, I have been thinking of searching for some ear plugs that heavily attenuate the low freq. (-20db @ below 200 Hz?), yet pass through most sources above 2500 Hz. (so I don't miss sirens). Passive resonances may be addressed w/ acoustic damping material like Dynamat. Applied to bare metal surfaces of the interior, it is not too heavy & will deaden resonance. I have found 3M Rubberized Undercoating to be effective. It can be applied to the interior, under mats & in doors, since it isn't a heavy, smelly tar-rich material.
06-07-2002, 11:07 PM
#6
Former Vendor
I've used a dynamat equivalant (much less expensive!) in my truck. It made a big difference. Really gives it a solid feel and kills the high frequencies. I covered most every sheet metal surface that was accessible.
However a 911 is a different animal. I want to hear the 6 cylinder music and whir of the fan. I wouldn't think of cutting that down.
Further the 911 has a fair amount of sound deadening in it already. I suspect the improvement potential is less than I had in my truck.
However a 911 is a different animal. I want to hear the 6 cylinder music and whir of the fan. I wouldn't think of cutting that down.
Further the 911 has a fair amount of sound deadening in it already. I suspect the improvement potential is less than I had in my truck.
06-09-2002, 09:50 AM
#7
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I sympathise with you, I have recently purchased a 77 911 Carrera with a beautiful c2 update etc...
However the lovely note from the aftermarket exhaust becomes monotonous and echoes throughout the car between 2600 - 2900 rpm. Above this the sweet note is obviously louder however it doesnt seem to echo inside the car, easy answer keep it above 3000 rpm. But I dont think the police will accept my excuse. I personally am going to add some of the dynamat or similar product. I love the porsches note but sometimes it can drive you crazy no matter how fanatical you may be.
However the lovely note from the aftermarket exhaust becomes monotonous and echoes throughout the car between 2600 - 2900 rpm. Above this the sweet note is obviously louder however it doesnt seem to echo inside the car, easy answer keep it above 3000 rpm. But I dont think the police will accept my excuse. I personally am going to add some of the dynamat or similar product. I love the porsches note but sometimes it can drive you crazy no matter how fanatical you may be.
