Understanding Impact (Footfall) Noise
Impact noise is increasingly becoming the most common noise complaint
around the world. Typically this would be in the form of footfall
noise between floors in apartments. Although one of the most difficult
to deal with Impact Noise can be effectively treated if the correct
techniques are used. This type of noise problem is always best
treated at source and is much easier to deal with if the floor
has a carpet finish.
By looking at the pictures below you can see how treating and
not treating the floor effects the level of sound which passes
through the construction.
Before Sound Proofing Treatment
After Sound Proofing Treatment
Floating Floors
The
term ‘floating floor’ is widely
used for many types of products and systems. Usually these all
have the same
common effect, separating the sub floor and the final floor finish
via an impact absorbing layer. The impact absorbing layer cushions
the impact so that much less energy is delivered to the floor and
into the structure.
Floating floors can be created on concrete or timber constructions
and can be finished with tiles,
hardwood, laminate flooring, carpet, etc.
Look at the list below to see which products can be used as a
resilient layer to create floating floors
NoiseStop Isolation Mat (Buy Now)
NSSF7+ (Buy Now)
NoiseStop Impact Foam (Buy Now)
Effect of floating floors
Resilient layers used to create floating floors keep energy from
reaching the sub floor below. The impact is cushioned so that less
energy is delivered into the floor and into the structure. High
frequencies are reduced much more effectively but the effect decreases
as the frequency declines. The main benefit from resilient layers
is that they help reduce the energy of sound in all directions.
Using resilient mounts
Resilient mounts or SoundBreaker Bars can be very effective in
helping reduce impact noise passing through a ceiling be creating
mechanical isolation and reducing the possibility for conduction.
SoundBreaker Bars are limited to only reducing the noise going
directly through the floor but when used in conjunction with a
resilient mount, such as NoiseStop Isolation Mat, the results can
be very positive.
To get the best from resilient mounts always make sure you have
dealt with any flanking paths. As discussed in the Flanking Noise
section, a construction can only perform as good as the level of
Flanking Noise. In some cases this may require the treatment of
the walls in the receiving room.
Damping or Viscoelastic Damping
Damping is a very effective and cheap method for reducing impact
noise. It works by lowering the amount of noise generated by
an impact by dissipating vibration quickly as it moves through
the structure, thus lowering impact noise.
Damping is quite unique in that it is effective at reducing noise
levels across the entire frequency range with no noticeable weakness
at low frequency. By dissipating the energy it mitigates flanking
noise and minimizes the level of structural noise going through
the construction.
The use of damping should only really be reserve for floor constructions.
Although damping techniques can be used for ceilings, like SoundBreaker
Bars, damping materials cant reduce the amount of noise created
at source or help reduce flanking paths when not in the floor.
Mass
Mass can have a small effect on impact noise however it is usually
more valuable in stopping airborne noise. This method of insulation
should be the least favored when looking at impact noise alone.
Sound Absorption
Applying an insulation in a cavity should always be top of the
list. This can be in the form of a simple mid density Dense Fibre
Matting at 45kg or the high density Dense Fibre Matting at 140kg.
Although generally for absorption the density of the material has
no great affect, using higher densities only help to improve the
overall mass of the construction.
