Basics of soundproofing a car
There’s a huge amount of terms out there – sound deadening, sound dampening / damping, sound insulation, and so on, all these terms are parts of the concept of soundproofing. In fact, soundproofing consists of a number of key aspects – sound dampening, vibration dampening, sound insulation, sound absorption, and so on.
Automotive soundproofing is a tough concept, not only because there’s a limit as to the type and quantity of materials we can use but also because there is a large amount of various sources of noise, each producing different frequency.
There is no magical material out there that can efficiently stop noises of all frequencies – sound travels through any medium at different rates. The only way to efficiently reduce noise levels in the car is to use multiple layers of different materials, each dealing with a specific issue.
There are a few basic types of materials out there:
1. Vibration materials
When sound travels through a solid medium it becomes vibrations. These materials are aimed at lowering vibrations of the car frame and have to be applied directly to the inner parts of the metal frame.
2. Dynamic vibration materials
Vibrations can be reduced by few different means, traditionally it has been done with butyl based materials which add mass and absorb vibrations. Dynamic materials add much less mass, but instead they increase the rigidity of the frame. Most of them come in a form of liquid mastics which harden when applied to the surface.
3. Sound materials
These materials are aimed at preventing passage of sound waves and are generally applied on top of vibration materials. There are two distinct groups of materials here – sound insulators and sound absorbers / dampers. The first group works by blocking and reflecting sound waves and the latter absorbs sound waves converting the energy into tiny amounts of heat.
These materials simply prevent airborne noise from passing through holes, they are used to fill in any spaces that would otherwise tunnel the sound directly from outside or engine.
5. Contact dampers
Frequently, especially in the older cars, we get to hear a fair bit of rattling and squeaking sounds coming mostly from parts of interior moving around while driving the car. Contact damping materials are aimed at removing those sounds.
Each area in the car has different noise loads from various sources of noise – for example there isn’t going to be much wind noise coming from the floor, or engine noise coming from the roof. It would make absolutely no sense covering every bit of the car with the same single material, well it would have results, but they will be very minimal and very far from optimal.
Achieving maximum results is about balancing a few variables such as added weight, effective noise level reduction and cost, we will discuss this at more depth in one of our upcoming articles.