A quick lesson in acoustic
attenuation :
Sound is the result of the disturbance of the eardrum by the impact of
acoustic waves (vibration). The amount of energy contained in those waves
(amplitude) and the time between the impact of consecutive waves
(frequency) determine the strength of the disturbance of the eardrum
(volume).
Noise is often thought of as simply being too much volume. While this is
one type of noise, there are also others. A particular frequency or
combination of frequencies may be low in volume but still be considered
noise. Therefore, noise is the subjective interpretation of a physical
phenomenon.
Sound attenuation is the conversion of the energy contained in acoustic
waves into heat. This is accomplished by making the waves move other
objects (work) at a frequency outside the range of human perception. If
the objects themselves move at a frequency within the range which can be
heard, the sound is simply transmitted.
Whatever the definitions, most people simply want to make it all go away.
Clear enough but not all that easy. The subjective nature of noise
complicates attenuation. One person may not mind low frequency sound but
is irritated by high frequencies. Another person may be just the opposite.
Why not just reduce all frequencies?
While that is usually the goal, there is no single material that
accomplishes it. Most materials are effective at converting only a very
limited frequency range (narrow spectrum). Given enough thickness, any
material will eventually convert all sound energy to heat. However,
achieving effective wide spectrum sound reduction within a limited space
requires that different materials be composited together in a compatible
manner. When constructing these laminates, the types of materials used,
the sequence in which they are laminated and the method of construction
combine to determine their effectiveness.
Why some sound attenuation materials better than others.
All sound attenuation materials are a compromise. The compromise may be
space, weight, complexity, cost or any combination of factors. For many
reasons, what is effective in one situation is not suitable for another, A
12" thick concrete wall is fine for attenuating sound along a freeway but
isn't great for a boat. Deciding whether to trade performance for cost,
thickness for weight and so forth is a choice that manufacturers must make
based of their market.
Where a manufacturer chooses to compromise is one important point of
product differentiation. The other is engineering expertise. Many
"soundproofing" materials on the market are little more than one or more
generic foams glued together with a Mylar facing. Coming up with a
superior sound attenuation product requires innovation, research, testing
and engineering expertise - hallmarks of Glacier Bay, Inc. since 1990.
What about low-frequency noise?
Low frequencies are considerably harder to attenuate than higher
frequencies. They are also the most common type of noise found on boats.
Inch for inch you can't do better than BARRIER Ultra-dB Flex in a flexible
material. However, for maximum attenuation, particularly at low
frequencies, abandon the convenience of flexible products and back the
Ultra-dB Flex with BARRIER Ultra-db Panel. Incorporated into a
proper enclosure design, you just can't get any better.
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