Reducing noise with the VoltShelf

Both 406 Coupé and C6 had a closed boot, separated from the cabin with metal and an additional parcel shelf trim on top. This would help keep the noise that originated in the boot contained.

With the Ampera, probably to reduce weight, a tiny fabric piece was used as a divider between the boot and the rest of the interior. It doesn't give much protection from onlookers, the sun or any noise. Also it's not practical, if the car is a hatchback would make more sense that a parcel shelf would be elevated when opening the boot.

Even before buying the car I already had my eye on the VoltShelf and after much reading on the various forums dedicated to the Volt / Ampera found out that there was also some noise reduction.

Although it's main purpose is not sound deadening, and for the ones reading this without an Ampera or Volt, this step won't help much to give you new ideas to reduce noise on an electric car, I was curious and decided to share what the differences where after installing it. After all when deadening we are either adding mass to dampen metal or adding noise barriers, and the shelf is in itself a barrier between the boot and the cabin. But how effective will it be?

First, a look at the original fabric shelf

The Ampera was created with weight reduction in mind. It is visible in multiple areas of the car, and even with the materials used for deadening from factory.

The shelf is one of those areas, with a flimsy fabric shelf that is a pain to use because it limits the opening to the boot by quite an amount.

Original fabric shelf
Original fabric shelf
Fabric shelf unhooked
Fabric shelf unhooked

It doesn't cover the entire boot, allowing to see when you have large items stored there and there is zero difference in terms of noise reduction with the fabric in place or not.

VoltShelf, aftermarket

The VoltShelf is very light, probably less than 1Kg, I haven't weighted it because I would add it either way, it's purpose for me is not sound deadening, that is just a plus. So I won't be adding the weight of the shelf into the deadening stats for the Ampera.

It makes loading things to the boot much easier, allows more light in and gives a better finish to that area of the car.

VoltShelf in place
VoltShelf in place

Installing is somewhat easy, but I find the process of adjusting it's position with knots and bungee cord a bit fiddly. I'm not 100% committed to the way it is installed and will be experimenting to try and make it stay a bit higher in the boot to give me more space for cargo.

There are two metal supports that keep the shelf in place when the boot is closed, but these rattle ever so slightly in bad roads. If I'm keeping these supports I might add double sided tape to keep them in place and probably add some foam or Dynaliner to decouple them from the plastic and stop it making noise in roads with potholes.

The results

At idle there is no difference, probably because the only noise coming from the boot with the car stopped is from the fan near the 12v battery, and that only is audible when the car is charging, so makes sense that the values would be the same.

But as soon as I drove the car out of the garage it was noticeable that the rear end of the car was quieter.

Measuring at 80km/h I got a slight reduction of half a decibel and at 120km/h there was no difference in the meter, but the tire noise was not as audible from the rear. It makes sense as at speeds above 100km/h wind noise becomes the worst offender in terms of noise, and today was a very windy day.

Another thing that would annoy me was the sound of things in the boot moving around. I did test this with a bag in the boot, and it is a bit more muted but still audible.

This was a modification that I would make without regard for sound deadening, but happy that I got some good results in reducing noise.

Opel Ampera
Done in 25 of April, 2018