Environmental Engineering Reference
In-Depth Information
Schock Absorber
FIGURE 7.8
Shown.is.a.shock.absorber.to.dampen.vibration.and.noise.
and.hydraulic.shock.absorbers.commonly.take.the.form.of.a.cylinder.with.
a. sliding. piston. inside.. The. cylinder. is. illed. with. a. luid,. such. as. hydrau-
lic. luid,. or. air.. This. luid-illed. piston/cylinder. combination. is. a. dashpot..
Shock.absorbers.include.cushions.and.springs..The.shock.absorber's.duty.is.
to.absorb.or.dissipate.energy..One.design.consideration,.when.designing.or.
choosing.a.shock.absorber,.is.where.that.energy.will.go..In.most.dashpots,.
energy.is.converted.to.heat.inside.the.viscous.luid..
7.5
SoundEmissions,TemperatureandPressure
Upwind. rotor. emissions. and. downwind. rotor. emmisions. are. shown. in.
Figure 7.2..Sound.and.pressure.wind.waves.distribution.are.represented.in.
Figure 7.4.
Sound. has. different. frequencies,. e.g.,. human. hearing:. 20. to. 20,000. Hz,.
infrasound.less.than.20.Hz..The.threshold.level.of.hearing.at.10.Hz.is.equal.
to.100.dB..Following.Rogers,
2
.the.standard.deviation.of.threshold.of.percep-
tion.level.is.6.dB.
Broadband.sound.power.level.L
wa
.versus.wind.speed.correlates.with.nor-
mal.distribution.law..Noise.propagation.model.works.as:
.
L
p.
=.L
w.
-.10.log
10
(2πN
2
).-.αN.
(7.10)
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