To see how this works, let’s look at how a soundproof room is constructed. The same
principles apply to soundproofing a room as soundproofing a vehicle. So, picture a recording
studio – go ahead and put your favorite musician in there.
If you are like most people, you might be picturing a room with walls that are covered with
a thick foam padding that has a pyramid-shaped texture. But that soft foam is not a noise
barrier. In fact, if there was a wall made only of that soft foam separating you from
another person, you would be able to converse through it because sound easily penetrates the
soft foam. Then why is the foam there? Because instead of blocking noise, the soft,
lightweight foam is excellent at absorbing sound and quelling light echoes. That’s all it
Then what prevents outside noise, like the sounds of street traffic or of the rock group
next door, from entering the recording room? The actual sound barriers are installed inside
the walls where you can’t see them. Those barriers are solid, thick, somewhat heavy, and
fairly flexible. Traditionally, huge sheets of lead (yes, the metal lead) were nailed inside
the walls of soundproof rooms. The lead sheets covered the entire framework of the rooms end
to end, and from floor to ceiling. Technology has advanced a lot since then, but why was
lead used? Because to be an effective blocker of sound, a material must be 3 things:
you need at least one pound per square foot to effectively repel sound waves (and the
heavier the better). Otherwise sound would travel right through it like the soft foam.
the barrier should be somewhat malleable and soft to absorb the energy of noise vibration
and to prevent it from resonating
any gaps in the barrier are gaps that sound waves can travel through
Nowadays, a new sound barrier material is used in the place of lead in buildings, and it’s
great for vehicles as well. It is called mass loaded vinyl, or MLV for short.
The name comes from the way the material is manufactured. To increase the mass of the vinyl
sheets, heavy metal particles are mixed in during the manufacturing process. That extra
weight creates an effective sound blocker. The material is left somewhat limp, and that,
like the soft lead, prevents the material from resonating as it blocks sound waves. Working
together, the mass and the limpness create a sound barrier.