Sound deadening materials
 

Hello all. I was considering what I could do to enhance my 412 and making it a bit quieter inside would be a real plus. It has standard carpet underlay, no bulkhead insulation and intriguingly closing the air vents has a tremendous positive effect on improving a sense of solitude when driving

What recommendations would you make to address this? I have had a look at few options on the internet, but as to whether they are effective or not, I have no idea

regards

Paul

Trade it in for a Blenheim 4 !

Or drive a Land Rover for a week and it will seem silent

Or buy a louder 8 track

Or wear a motorcycle helmet

Or fit Fraser Nash electric motors to each wheel

Or cover everything inside with Dynamat like on the Yanky custom car shows

Hope this helps :-)

Have tried one of the above!....does Dynamat work?

P

Yes - it works very well and makes the radio / 8 track sound better too !

I am very tempted to get an eight track, maybe Tadpole Radios could convert it to keep the 8track and allow it to connect to a modern stereo.

I am going to have a look at Dynamat later at the local stereogram shop

P

Go for it !

Vintage 8 track player in dash expo streamline model unused & boxed | eBay

I glued sheet roofing lead to the petrol tank in my 411. It was very effective at stopping the sound of fuel sloshing around in the tank.

Sound is transmitted into the car by panels (side or floor) vibrating. You can either suppress the sound transmitted by the vibrating panel, or stop the panel vibrating in the first place, by adding mass to the panel. Lead does this very effectively.

You need to differentiate between damping panel resonance and vibtration (which is what Dynamat and the like do) and actually blocking sound.

Dynamat-style resonance dampers aren't designed to be used as a sound barrier and it's only necessary to cover about a third of a vibrating/tinny-sounding panel for the damper to be effective.

To actually stop the road/engine/exhaust noise getting into the interior you need a contiguous barrier layer, which needs mass (e.g. 5 kg/m mass-loaded vinyl, lead sheet etc.). To gain maximum benefit this layer needs to be as complete as possible (taped joins, no gaps) and to be decoupled from the floor/bulkhead/whatever by a layer of something like closed-cell foam (which might also help absorb some high-frequency noise).

What Philip says is all true.

A company called Noisekiller Acoustics makes a range of materials. They have a dynamat-type stick-on material and also a heavy-ish foam backed rubber material which can be cut to shape and laid under carpets, etc. this material is flexible engought to shape around trans tunnels, etc.

If the air vents make a big difference, and if in that sense you would be quite happy with the refinement of the cabin if the air vents could always remain shut, then your problem is (obviously, I suppose) noise transmission through the vent system. The way to tackle that would be by lining various parts of the vent system with sound absorbing materials. They should also be fire resistant, of course. A sound absorbing material is a material with a sound-porous surface, and a layer below the surface which absorbs and breaks up the air vibrations. This might take the form of a thin layer of perforated but closed-cell foam over a layer of open-cell or even reticulated foam.

On some noisy semi-race engines I have had some success by just lining the induction air pipes with a fire-retardent reticulated foam.

I did what you're proposing on my Jensen CV-8.
You might find this thread helpful.
Wind down a bit to get past the nonsense and it becomes pertinent.
The attention I paid to the doors was also very effective.


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[quote=Thor;5874]What Philip says is all true.

A company called Noisekiller Acoustics makes a range of materials. They have a dynamat-type stick-on material and also a heavy-ish foam backed rubber material which can be cut to shape and laid under carpets, etc. this material is flexible engought to shape around trans tunnels, etc.


I have taken the plunge and bought some Dynomat Extreme which I have used to cover everywhere aft of the front of the rear seat. A slight nuisance is that the tunnel carpet is glued down. It has made an appreciable difference, principally getting rid of high frequency noise. This could of course be entirely imaginary. I have bodged the doors for now as I have lost the allen key I need to take the inners off so I only covered what I could reach through the speaker aperture. I have ordered the engine bay version of Dynomat, but I think I will have some fun trying to apply it to the engine bay, but I will see how I go.

I looked at noisekiller. It is cheaper than Dynomat, I might order some for the doors to compare it.

The main thing I want to eliminate is the sewing machine engine noise. I will report back.

P

It looks as if it might just fit in the second slot in my center console. I am trying to find out the dimensions. I really like the idea of being able to kick in an eight track. The next challenge will be wiring it into the existing system, I should be able to route it though the Aux input on the more upto date head unit.

I might have to strip out all of the sound deadening in a bid to mask the sound quality!

P

I've heard numerous different descriptions of the noise a V8 engine makes, but that's a first for "sewing machine"!

To my mind 'sewing machine' noise is high frequency noise. This is usually air-born noise, rather than due to structural vibrations, it is less likely to be stopped by dynamat and the like than by sound absorbing materials (as opposed to vibration dampening materials).

Being a Discovery channel addict , a few months ago I remember watching a programme about counter acting the noise in an aircraft cabin. I didn't fully understand it , but basically a computer controlled gizmo created a noise opposite to the noise in the cabin which led to the cabin noise being cancelled out !

The result was spectacular and better than any amount of sound proofing could do in a prop plain. I would like to think that this technology would eventually become economically viable to use in a car ! Or better still my living room :-)

For now , I will just turn the radio up a bit

Greg, Lotus have done loads of work on this area, but I think the car cabin has too many different sources of sound, and resonances mean that a sound which is intense in one area is less noticeable in another, so the only pratical location for the sound removal devices is close to the ears of the users.

They use a system like this, built into the headphones/ear defenders of air force pilots.

Lotus did achieve exhaust silencing without the use of conventional silencers and, of course, this work lead to the idea of making a cheap front wheel drive shopping car sound like a Dodge Charger Hemi for no extra cost.

Amazing ! thanks for the information - love all that sort of stuff !