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your eyes dilate; the small blood -vessels in
<br />your skin contract; your blood pressure
<br />rises. These are the actions of a body
<br />arousing itself to escape. During sleep the
<br />sound level. need only exceed 55 (lit toy
<br />produce changes resembling the waking stress;
<br />for 70 dB. '
<br />You can become "accustomed" to the
<br />noises in your environment. but all that
<br />this means Is that you can become accustomed
<br />to cllminatinl; the noise from your conscious
<br />nttention. The physiological effects
<br />persist. If you are compelled to work in
<br />noisy surroundings, the- only warnings of
<br />:u:on.t Ical]Y-.Lnduce(I stress may he sipns of
<br />fatigue and nervous strain.
<br />1::xper[ments with nnesthetized animal,
<br />show than the stress reactions persist at
<br />the same levf•ls whether'or not the animal Is
<br />aware of them. Adaptation to the s1:rr.ss
<br />dues not orrur. Studies of noise reactions
<br />of people living in crowded neighborhoods
<br />also have shown that, over a period of
<br />years, the rate and kinds of complaints
<br />about noise did not change.
<br />No one knows how many of tile.
<br />atres,t-indnrrd dtsenses of our modern era
<br />are made more prevalent by the rising noise.
<br />levels In our densely -populated cities.
<br />l: t Ihat (he.:e 1eve Is do not affect
<br />11"ar11)l;. .:or d;� the results mean that all
<br />n)l.e ,hould be excluded. Studies of the
<br />effects of noise upon wort: indicate that
<br />some degree of ambient: sound (which might as
<br />(sell be paras:ant, such as the sounds of a
<br />fountain, or background mus Lc) helps
<br />maintain arousal during repetitious tasks;
<br />only the vary highly -demanding mental tasks
<br />are done Netter in wholly quiet
<br />surrot,ndingr..
<br />Noise damage to hearing is an insidious
<br />process. The Innnedtate effvct s do not
<br />always indlcate the ulLimate results of
<br />exposure. Exposure to a mildly er.ce,r:ivc
<br />noise level results In a temporary
<br />de,ensLtfzatton of the ear, the so -called
<br />"t.emporary threshold shift", a temporary
<br />However, this pattern of threshold nine
<br />and recovery sometimes goes on through a
<br />number of cycles without any further
<br />ev.tdeitce of damage, and then there may be n
<br />sudden failure co make complete recovery.
<br />This permanent: effect - "noise-induce(I
<br />permanent tItreslit) I d shaft", sometimes
<br />abbreviated in capitals as NIPTS - is a
<br />sensorineural hearing loss. That is, the
<br />damage is located at the auditory nerve,
<br />itse.lf:,'with serious consequences.
<br />Studles of NIPTS over a period of I:Imc
<br />have (shown some evidence that person. are
<br />particularly .likely to suffer hearing damage
<br />when they are going through pity, io.logIraI
<br />change or enduring physical stress such as
<br />rapid growth or illness. Thus, the common
<br />practice among, teenagers of listening to
<br />extremely loud amplified mu,ic for long
<br />periods of time, espec.lall.y through
<br />earphones, may have very serious
<br />consequences. Young persons:. In particular,
<br />frequently engage in several Irtiv[Lles each
<br />of which may be sufficiently noisy to
<br />constitute a hearing hazard. For example,.
<br />It in not unusual. for a high school student-
<br />to
<br />tudentto earn spending -money during srn•tmor
<br />vacation by mowing; neighborhood :lawns with a
<br />I.ypIcaI, usually very noisy, power
<br />The same per -on also may rehearse sev,•ral
<br />hours a week with a loud rook and roll )tan:!.
<br />Lhen play for hours aL the Saturday nll:ht
<br />dance. And f ina.11y for erciI:em, •nU 1r
<br />recreation, the sLudont. may upend air:
<br />leisure time riding a powerful but 110 !!:y
<br />motorcycle., water skiing behind a 1111:.-,
<br />high - speed motorboat, or perIInp^ !:1(ec•t•
<br />shooting at the gunnery rnuge. A]thouc;h no
<br />one of these actLv.ltIes may catu.e army
<br />lion rtng impairment for short or inftegnent.
<br />exposures, Lhey cannot be taken all toga•thrr
<br />at frequent JitLervrtls without rl-1l,lug
<br />hearing damage.
<br />P11ECAUTIONS
<br />WARNING 01: Because we hove no rcllable
<br />way to predict. the degree of permanent: lo.s
<br />from temporary tItreshoI(I shift, a
<br />conservative policy is to avoLd situation,
<br />Chapt.•r
<br />7 .Tt�lf7/�t'/f
<br />..- -• y' � d
<br />NOISE AS A 1 EAL I'll HAZARD
<br />When you are In n sound field whose
<br />lons of the ability to detect faint sounds.
<br />level
<br />a. read oil it r+ututd•-level meter in 70
<br />Noliten :Ilkcl.y to muse a temporary threnhold
<br />(lit or
<br />more, even though you know consciously
<br />shift are encountered during subway rider;
<br />that
<br />you art, In no hnzard, some part of your
<br />and -aIr.pl.ane Lt- Ips. Sonic degree of
<br />body
<br />tries to run away. The signs of this
<br />temporary threshold shift may be detectable
<br />are
<br />the common symptoms of nervous stress:
<br />even on the day following exposure, but
<br />Your
<br />heart beats more quickly; breathing
<br />ultimate recovery cnn be complete.
<br />becomes shallower and faster; the pupils of
<br />your eyes dilate; the small blood -vessels in
<br />your skin contract; your blood pressure
<br />rises. These are the actions of a body
<br />arousing itself to escape. During sleep the
<br />sound level. need only exceed 55 (lit toy
<br />produce changes resembling the waking stress;
<br />for 70 dB. '
<br />You can become "accustomed" to the
<br />noises in your environment. but all that
<br />this means Is that you can become accustomed
<br />to cllminatinl; the noise from your conscious
<br />nttention. The physiological effects
<br />persist. If you are compelled to work in
<br />noisy surroundings, the- only warnings of
<br />:u:on.t Ical]Y-.Lnduce(I stress may he sipns of
<br />fatigue and nervous strain.
<br />1::xper[ments with nnesthetized animal,
<br />show than the stress reactions persist at
<br />the same levf•ls whether'or not the animal Is
<br />aware of them. Adaptation to the s1:rr.ss
<br />dues not orrur. Studies of noise reactions
<br />of people living in crowded neighborhoods
<br />also have shown that, over a period of
<br />years, the rate and kinds of complaints
<br />about noise did not change.
<br />No one knows how many of tile.
<br />atres,t-indnrrd dtsenses of our modern era
<br />are made more prevalent by the rising noise.
<br />levels In our densely -populated cities.
<br />l: t Ihat (he.:e 1eve Is do not affect
<br />11"ar11)l;. .:or d;� the results mean that all
<br />n)l.e ,hould be excluded. Studies of the
<br />effects of noise upon wort: indicate that
<br />some degree of ambient: sound (which might as
<br />(sell be paras:ant, such as the sounds of a
<br />fountain, or background mus Lc) helps
<br />maintain arousal during repetitious tasks;
<br />only the vary highly -demanding mental tasks
<br />are done Netter in wholly quiet
<br />surrot,ndingr..
<br />Noise damage to hearing is an insidious
<br />process. The Innnedtate effvct s do not
<br />always indlcate the ulLimate results of
<br />exposure. Exposure to a mildly er.ce,r:ivc
<br />noise level results In a temporary
<br />de,ensLtfzatton of the ear, the so -called
<br />"t.emporary threshold shift", a temporary
<br />However, this pattern of threshold nine
<br />and recovery sometimes goes on through a
<br />number of cycles without any further
<br />ev.tdeitce of damage, and then there may be n
<br />sudden failure co make complete recovery.
<br />This permanent: effect - "noise-induce(I
<br />permanent tItreslit) I d shaft", sometimes
<br />abbreviated in capitals as NIPTS - is a
<br />sensorineural hearing loss. That is, the
<br />damage is located at the auditory nerve,
<br />itse.lf:,'with serious consequences.
<br />Studles of NIPTS over a period of I:Imc
<br />have (shown some evidence that person. are
<br />particularly .likely to suffer hearing damage
<br />when they are going through pity, io.logIraI
<br />change or enduring physical stress such as
<br />rapid growth or illness. Thus, the common
<br />practice among, teenagers of listening to
<br />extremely loud amplified mu,ic for long
<br />periods of time, espec.lall.y through
<br />earphones, may have very serious
<br />consequences. Young persons:. In particular,
<br />frequently engage in several Irtiv[Lles each
<br />of which may be sufficiently noisy to
<br />constitute a hearing hazard. For example,.
<br />It in not unusual. for a high school student-
<br />to
<br />tudentto earn spending -money during srn•tmor
<br />vacation by mowing; neighborhood :lawns with a
<br />I.ypIcaI, usually very noisy, power
<br />The same per -on also may rehearse sev,•ral
<br />hours a week with a loud rook and roll )tan:!.
<br />Lhen play for hours aL the Saturday nll:ht
<br />dance. And f ina.11y for erciI:em, •nU 1r
<br />recreation, the sLudont. may upend air:
<br />leisure time riding a powerful but 110 !!:y
<br />motorcycle., water skiing behind a 1111:.-,
<br />high - speed motorboat, or perIInp^ !:1(ec•t•
<br />shooting at the gunnery rnuge. A]thouc;h no
<br />one of these actLv.ltIes may catu.e army
<br />lion rtng impairment for short or inftegnent.
<br />exposures, Lhey cannot be taken all toga•thrr
<br />at frequent JitLervrtls without rl-1l,lug
<br />hearing damage.
<br />P11ECAUTIONS
<br />WARNING 01: Because we hove no rcllable
<br />way to predict. the degree of permanent: lo.s
<br />from temporary tItreshoI(I shift, a
<br />conservative policy is to avoLd situation,
<br />
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