Thread: Sound Proofing

Originally Posted by Lotz-A-Landies

Shorty

That is exactly the sort of product I'm looking for - in the S2B you sit directly over the engine and wheels with only a 2 mm thick flat sheet of aluminium between. That is why a friend has ear muffs for the passenger.



Unfortunately it's illegal for the driver.

Diana

And so it should be. I damn near got run over in Adelaide years ago. Idiot driving a Moke, wearing stereo headphones plugged into his radio.

That is a neat S3 dash in that S2, or am I mistaken again.

Noise also comes from drumming, panels which are bare...and vibrate like a drum skin.

If you want to go for the sound recording studio deadening, most studios use Sonex, amazing stuff, flexible, and looks pretty cool, too!

This'll give you a hint: http://www.sonex-online.com/


GQ

they would be great to stick to the turret of a fender......only problem is.....they absorb moisture....they are a type of sponge.....

Originally Posted by Quiggers

Noise also comes from drumming, panels which are bare...and vibrate like a drum skin.

If you want to go for the sound recording studio deadening, most studios use Sonex, amazing stuff, flexible, and looks pretty cool, too!

This'll give you a hint: http://www.sonex-online.com/


GQ

My, how things change.

I can still remember a school trip to channel nine in Adelaide, way back in the sixties. They were using egg cartons for studio soundproofing in those days.

Probably not water-proof enough for a Landy.

egg cartons will work as well.......


its the actual shape of them that absorbs the sound......
basically......theres no flat surfaces for the sound to reflect/bounce off........
so it bounces around in the valleys and gets broken down till theres nothing left......


sooooo..........the more times you roll your rig and dent the roof and panels........the quieter it should be......

Here are some notes on sound insulation that you may find useful.

Before I go into details, there are two modes of sound transmission, and one of sound "amplification" The first mode of transmission is airborne and the second structure borne. Ultimately, you must ensure that both are dealt with to get noticable noise reduction in the cabin. In addition the "sound amplification" I'm talking about is the sound reverberation buildup in the cabin, if the cabin is bare / has a lot of exposed metal / glass.

Transmission

Airborne noise is cheaper to deal with of the two, but it is more difficult, given Land Rover's superb door sealing qualities and the multitude of firewall openings behind the trim. However, it should be tackled first.

You'll find this will also help with airconditioning, for those "lucky" enough to have it.

So, before you lay out any insulation on the floor etc, make sure the cabin is well sealed from the the underside (exhaust) and from the engine compartment. This means ensuring all door seals (especially the back door) sit firmly against the door when closed, and that there are no gaps in the seal, especially at the bottom corners, where two different sections of seal meet. As a rule of thumb, if you can see the pavement , it is definately not well sealed!

Secondly, seal all wiring access holes in the firewall. When I say seal, use something like flexible mastic, which will allow movement of the wires without the seal cracking. Make sure the mastic is a skinning type, otherwise you'll end up with a mess. If you're finding that skinning mastic isn't strong enough to hold in place, you could try silicon.

Once you are certain that the cabin is well sealed, you can proceed to insulating the floor to deal with structure borne noise transmission.

Outside noise induces vibration in the floor panels, which then radiate noise into the cabin. The panels will be more efficient at radiating at certain frequencies than at others, depending on the shape, density and rigidity of the panel material. Noise transmission into the cabin will be the worst when the exciting frequency matches the resonant frequency of the panel.

For low frequency engine and exhaust noise, lead sheeting is by far the best. It has a very high density and low rigidity. The critical frequency will be well into the ultrasonic range. If you can line the underside of the car (from either inside or outside) with 1 mm or 2mm lead sheeting, you'll be doing quite well. I'd use a thin foam lining on the underside of the lead so that you don't get metal on metal rattle.

As pointed out earlier, it may be difficult to secure in place - This may have been the reason for lead sheeting with foam on either side mentioned in one of the other threads. I have not gone through the process myself yet, so unfortunately I can't give you too many practical tips. I am an acoustic engineer, however, and have come accross many similar problems in building applications.

Reverberation

Many of the older Defenders / countys and series vehicles have a lot of bare metal within the cabin (in addition to all the glass), so the cabin is highly reverberant (sound bouncing around for a long time, because there is little to absorb it). This results in significant increase in noise levels inside the cabin. I recently bought a Defender 90 panelvan with a stright-through exhaust, and next to no floor coverings - I should know!

This is what I've done so far, and what I plan to do.
I've used high density short pile marine carpet with a rubber backing to line the back area, with noticeably improved results. I also plan to line the rear panels with 50mm polyester batting behind a perforated metal sheet, to help with sound absorption wintin the cabin even more. (admittedly this may be a bit of overkill, but I also think it will improve the looks / practicability of the cargo area.

When I get time, I'll look at sealing the doors and firewall, and then I plan to line the cargo area with 1mm lead sheeting with a very thin underlay. I still have to think about what the impacts of lead in direct contact with aluminium have on corrosion.

Anyone with a son or daughter doing Yr 12 chemistry??


Also, to dispel a common myth, the foil has no effect on noise transmission. It is acoustically transparent, as it has no weight. Silver foil is a great heat reflector, and it is often found on insulating materials because they serve a dual purpose for insulation of both noise and heat.

Cheers

Forgot to mention windows - these also have to be "sealed" with rubber or silicone strips. Raven makes a great range of both rubber and silicone seals.

www.raven.com.au

Cheers

are you making fun of us..........mentioning defenders AND door seals in the same sentence......?