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The different sound source noise with different frequency characteristics,
some of the noise of low frequency energy, such as pump, gear
rotating machine, some sound source frequency energy, such as
bearings, cooling tower water, some of the noise of high
frequency energy, such as AC and DC motors, transformers, valves
etc., but most of the noise is often a variety of frequency have
a great voice, but there is no rule. For all kinds of acoustic
materials, the acoustic performance is different under different
frequency conditions. Some material has good acoustic
performance of high frequency, low frequency sound absorption
material has some good properties, some material has good
acoustic performance of some frequency varies with. Sound
insulation and other acoustic performance is also true. So if
you think of a good sound insulation and sound absorption effect
should be selected for insulation and sound-absorbing materials.
Sound can be decomposed into a number of (or even infinite)
frequency components of the synthesis. In order to measure and
describe the frequency characteristics of sound, people use the
spectrum. Frequency representation of frequency doubling and 1/3
frequency doubling. The center frequency of the octave is 31.5,
63, 125, 250, 500, 1K, 2K, 4K, 8K, 16KHz ten frequency, a
frequency was two times the previous frequency, so it is called
the octave, two times the frequency bandwidth of a frequency and
also a frequency. In some of the more detailed requirements,
will be more fine frequency divided into 1/3 octave, is each
octave subdivided into three bands, the center frequency is 20,
31.5, 40, 50, 63, 80, 100, 125, 160, 200, 250, 315, 400, 500
630, 800, 1K, 1.25K, 1.6K, 2K, 2.5K, 3.15K, 4K, 5K, 6.3K, 8K,
10K, 12.5K, 16K, 20KHz and other thirty frequencies, a frequency
was 21/3 times before a frequency. In practical engineering more
concerned about the ear sensitive parts, in most cases consider
the frequency range of 100Hz to 5KHz. Frequency doubling process
is generally used in noise control. If the frequency component
of the sound is plotted into a curve, the spectrum is formed..
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