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Soundproofing my van conversion

My LDV Convoy van is very noisy! Any speed over 20MPH and the sound system becomes useless. If a sound meter is anything to go by, I measured 82dB whilst idling sat in the driving seat and well over 90dB on main roads. An idling bulldozer is around 85db and loud enough to cause hearing damage after 8 hours of continuous exposure.

How do I soundproof a van?

Sound and noise is generated in a few different ways. Rather than using a lot of one material, you have to do a few things, using a few different types of material, depending on how the sound is transmitted. Here are the three main ways to stop transmission of noise:

  1. Stop panels from resonating using a bitumen sheet (also known as roof flashing–this stuff). This is basically the same material as the branded sound deadening products but much cheaper. I used this in the engine bay, cab floor and foot well. It works incredibly well.
  2. Block sound using a mass loaded vinyl (also known as MLV). This stuff is very dense and is used to add mass to walls of building to act as a sound barrier and insulation. It does a great job of blocking sound. I used this on wheel arches, floor, the foot wells and the divide between the cab and engine bay.
  3. Absorb air-borne sound using an open cell foam and auto carpet. The foam can go pretty much anywhere in the cab and engine bay and mainly only absorbs the high frequencies. The auto carpet is good for anywhere inside the van, like on the floor and wheel arches.

This makes sense to me. Its not about using loads of one material. You have to do a few things using a few different materials depending on how the sound is generated and transmitted.

Materials used:

Quantity Item Description Cost Supplier
3 bitumen flashing sheet This is exactly the same material as the pro sound deadening stuff £18.13 Amazon and and Wickes
2 mass loaded vinyl sheet supplied as 2 lots of 900 x 600mm sheets £21.98 Ebay (sound-deadening-shop)
1 felt backed sound proof carpet 5FTX8FT6 10mm thick £24.99 Ebay (autobahnbarry)
1 20mm open cell foam I used this under the bonnet and inside of dash £29.99 Ebay
1 spray adheisive The cheaper stuff is just as good £4 Amazon and Boyes

I think the method I’m about to show you will have the most effect at reducing noise whilst driving, everything else will probably be marginal. Here is what I did…

Here are the 4 different materials I used for the sound deadening: bitumen sheet with sticky back, mass loaded vinyl, carpet and foam
Here are the 4 different materials I used for the sound deadening: bitumen sheet with sticky back, mass loaded vinyl, carpet and foam

Prepare vehicle for the soundproofing

I removed everything from the cab to expose the bare metal floor. Any rust or corrosion on the floor should be fixed at this point, and before the next step.

ldv van floor
Seats out and ready to work with

1. Stick down bitumen on doors, floor and engine bay

To use this in the most efficient way possible you just need to stick it to the areas that have the most potential to vibrate and resonate. There’s no need to cover the whole floor.

I tapped around the floor with a screwdriver and stuck down a square of bitumen in the area that had a drumming sound. This noticeably deadens the sound straight away–the panel will sound like a dull knock when it is tapped, rather than a more sustained boom.

If the temperature is very cold then you may need to heat the bitumen sheet slightly to make it tacky so it is in full contact with the metal. I applied the bitumen sheet to the cab floor, the inside of the engine bay  and on the inside of the door and body panels. See images below.

I tapped around with a screw driver. When I hear a drumming sound I stick a square of bitumen sheet down. This completely deadens the sound straight away. I was really impressed
Sticking bitumen sheet to cab floor
Sticking bitumen sheet in engine bay
Sticking bitumen sheet in engine bay
Sticking bitumen sheet on door panels
Sticking bitumen sheet on door panels

2. Cover the floor and wheel arches with mass loaded vinyl (MLV)

Now the mass loaded vinyl (MLV) goes down. I used two layers on over the gearbox, at the front of the foot wells and over the wheel arches where there is the most noise from the engine.

cab-floor-sound-proof
Now the mass loaded vinyl (MLV) goes down. This stuff is surprisingly heavy and is used to add mass to buildings and walls to act as a sound barrier
mass-loaded-vinyl-2mm-sheet
Here is what the MLV looks like. You can tear it easily and it will break up if folded aggressively which makes it quite easy to work with when it doesn’t matter about how it looks and often it doesn’t.
mlv-sound-barrier
I used a few layers over the gear box area. I also tried a new fixing method; the stapler. Its works well for temporary holding
Laying down the MLV on cab floor
Laying down the MLV on cab floor

3. Lay carpet on floor and wheel arches

measuring-carpet
Time for the carpet. How the hell do i fit this? I better learn how
glue-carpet-down
loads of spray glue. Glue and carpets – I really hate this combination but its all for the sound rather than to look nice.
carpet-round-wheel-arch
The wheel arch – always the awkward part but I may have just got away with it
laying-van-carpet
Pretty much done. I may go around to neaten it up at some point but its 10pm on a cold december night

4. 20mm foam under bonnet and on the inside of the dashboard

open-cell-foam
I used this 20mm open cell foam to put inside the engine bay and under the bonnet.
cab-sound-proof
This is the back of the dash/glovebox. I also used bitumen sheet again to stop the plastic vibrating
under-bonnet-foam
This stuff is self adhesive but I used extra glue because it is winter and everything is damp and cold
bonnet-sound-insulation
I stuck the foam on the back wall of the engine bay and under the bonnet
bonnet-sound-proof
I put back the under bonnet sound proofing back over the additional foam.

Update: I added some acoustic  foam

I found some studio grade acoustic foam on Amazon so I thought I’d stick some on the roof of the cab since it is made out of hard plastic and quite reverberant. This is only really going to dampen airborne sound in the mid to high frequency range. I’m not sure if it works but hey, it looks good and its worth a shot for the cost of 5 tiles.

acoustic-foam-van-cab

Results!

The difference is huge. It now measures 72db when idling which is 10db less than without the soundproofing! excellent results. The sound from the stereo has also dramatically improved which is something i didn’t even think about.

… and to wrap up in a few bullet points:

  • if I had the money I’d have multiplied the amount of materials by 3 but there’s a point where any more will have a very marginal effect.
  • you don’t need to go for the top branded sound proofing materials. Just get the basic generic material – its the same thing!
  • Laying carpet with spray glue on uneven floors doesn’t give pro results but certainly does the job

 

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