CIH-Noise and Vibration
If you are using a dosimeter with a 90 dBA threshold and a second dosimeter with a 80 dBA threshold to measure the same noise source, how should your 90 dBA threshold dosimeter's readings compare to your 80 dBA threshold dosimeter?
Less than or equal to
Given (X) dB at a point, what is the dB at a point 3 times distance?
Level 2 = level 1 + 20 log (r1/r2)= X + 20 log (1/3)= X + (- 9.5)
Sound intensity level is calculated using which formula?
Li = 10 log I/Io
Which three bones make up the ossicles?
Malleus, incus, stapes
The various units used to express noise include all of the following except:
Micronewton
Which part of the sound level meter is most effected by directivity, sensitivity, and level?
Microphone
You are called to do a noise survey because a person is complaining about speech interference levels. Which meter would you choose?
Octave band analyzer
Speech interference levels can be determined with which of the following instruments?
Octave band analyzers
Evidence suggests that short term occupational exposure to vibration causes which of the following?
Only small physiological effects which are reversible
Which term describes a physician specializing in diagnosis and treatment of disorders of the ear, nose, and throat?
Otolaryngologist
When one measures the acoustic energy produced by a device relative to some reference it is commonly designated as:
PWL.PWL is the Sound Power Level. It is a measure of the acoustic power in watts relative to a reference power (10-12 watts). The formula for calculating it is PWL=10log (W/Wo); where W is the measured acoustic power and Wo is the reference acoustic power.
Which characteristic of quantifying vibration levels does not take into account the time history of the wave?
Peak to peak
In worker's compensation cases for hearing loss the term high fence is often used. High fence also varies by state. What is the meaning of the term high fence?
Point of 100% hearing impairment
As one ages, there is a vascular and neural degeneration of the inner ear. This results in a decrease in hearing ability. This condition is called:
Presbycusis.
The unit dB has become popular for noise measurement because:
it covers a wide range of values.
The A-weighted sound level measurement is the preferred scale of measure because:
its weighting is related to effects of noise on the ear.
During noise level surveys the microphone should be:
operated according to manufacturer's specifications.
An octave is a:
portion of the sound frequency spectrum where the upper bound is twice the lower bound.The upper frequency within the octave band (f2) is twice the lower frequency (f1).Therefore:(f2) = 2(f1)
One of the hearing tests performed by audiologists and other qualified individuals involves placing noise producing devices on the Mastoid Process. The Mastoid Process is a:
set of bones extending down from the temporal bone.
An octave band analyzer is an instrument used to determine:
the noise frequency distribution.
What formula is used in time weighing noise environments to calculate noise dose?
(C1/T1 + C2/T2 .....+ Cn/Tn) = X
An ANSI Type 2 sound level meter has what accuracy range?
+/- 2 dBA
When damage occurs to an employee's hearing the result will be a standard threshold shift. According to OSHA, a standard threshold shift is an average decrease of _______ dB or more in the 2,000, 3,000, and 4,000 bands.
10
Atmospheric pressure can affect the measurement of noise. At what altitude should you become concerned about atmospheric pressure affecting noise measurement instrumentation?
10,000 feet above sea level
An octave band analyzer that measures 100 dB at 1000 Hz would measure what equivalent dBA level?
100
What would be the measured noise level 6 feet from a source in a reverberant field measured at 100 dB, 3 feet from the source?
100 dB
At a given intensity, sound in which frequency is most likely to result in permanent hearing damage?
1000.0 - 4000 Hz
An OSHA standard threshold shift is a change in hearing threshold relative to the baseline audiogram at an average of:
10dB or more at 2000, 3000, and 4000 Hz.
Type 2 sound level meters and dosimeters have an accuracy of plus or minus 2 dB within the frequency range of most interest in an industrial noise exposure. What minimum dosimeter reading is necessary to assure that you have measured an exposure above 90 dBA?
133%。133% is the minimum dosimeter read-out necessary to assure that you have measured an exposure at or above 90 dBA, given the limits of a type 2 meter. OSHA does not issue a citation until levels are above 133%. The lower confidence limit for the Type 2 meter equates to 75% dose.
The upper edge frequency of an octave band having a center frequency of 1000 Hz is:
1414
What is the normal hearing range for a human with good hearing?
20 Hz - 20,000 Hz
The AAOO-AMA "Guide for the Evaluation of Hearing Impairment" has a dB "window" at selected frequencies below which no impairment in hearing is accepted. What is this "window"?
25 dB
What is the limit of hearing damage, currently suggested by the American Medical Association, before compensation should be awarded?
25dB loss at 500, 1000, 2000 and 3000 Hz octave bands
If an industrial hygienist notices a definite reduction in noise in moving from one point to another, what minimum reduction would this represent?
3 dB
At what frequency does noise induced hearing loss first show up on an audiogram?
3000 - 6000 Hz
What is the initial geometric-mean frequency for a 10 band Octave Band Analyzer?
31.5 Hz
When a person is first exposed to hazardous levels of noise, the initial change usually observed is a loss of hearing about __________ Hz.
4,000 Hz
A sound absorption coefficient of 0.6 means that _____ of the sound energy in a wave will be reflected.
40%
When a person is exposed to high noise levels, a change in hearing is usually observed as a loss of hearing ability in which frequency range?
4000 Hz
What frequency range of hearing loss detected by an audiogram is generally considered compensable under worker's compensation?
500 - 2,000 Hz
Shock mounts are responsible for reducing especially which of the following frequency ranges?
500 Hz
A fan is used to discharge exhaust air to a stack. The fan has 20 blades and operates at 2000 rpms. The job assigned to you is to determine in which band to measure an octave band analysis.
500 Hz band In this case, measure in the 500 Hz band because:blade frequency = RPM * Blades/60= 40000/60= 666.7
The octave band center frequencies that most closely correlate with human speech are:
500, 1000, 2000, 4000
B-frequency weighting is intended to approximate the ear's response to sound levels between:
55 - 85 dB.
Audiograms are required for each employee exposed to noise at or above:
8-hour time-weighted average of 85 decibels.
Hearing protectors must attenuate employee exposure at least to an:
8-hour time-weighted average of 85 decibels.
Noise dosimeters accumulate noise exposure starting at what's called the threshold, beginning at:
80 dB;Noise dosimeters thresholds can be adjusted, but generally they accumulate noise exposure beginning at 80 dB. The original OSHA standard had a threshold at its criteria level of 90 dB. This lead to the condition where an 8 hour exposure at 89 equated to a dose of 0% while an 8 hour exposure at 90 dB equated to a dose of 100%.
If a material has a sound absorption coefficient of 0.8, that means that ______ percent of the sound energy in the wave will be:
80, absorbed.A sound absorption coefficient of 0.8 means that 80% of the sound energy in the wave will be absorbed and 20% will be reflected.
If a person is exposed to 88 dBA for four hours, to what level could he be exposed, if any, for the remaining four hours of his workday? (ACGIH standard)
88d BA for 4 hours is the ACGIH maximum daily noise exposure.
If engineering controls fail to bring noise levels within OSHA non-hazardous levels, at what point are hearing protectors required for employees?
90 decibels equivalent or greater for 8 hours
Which weighting circuits are incorporated into the sound level meter so that the meter has a response similar to the human ear?
A
How often should a sound meter be calibrated?
A. Before and after each use
The damaging effect of noise on hearing depends on:
A. the sound pressure level of the noise. B. the frequency distribution of the noise.
Transmission Loss is which of the following?
A.Frequency dependent C.Different for different substances
To reduce airborne sound produced by solid sources, which of the following action(s) should be taken?
A.Reduce the noise radiating surface area B.Provide an air leak in the solid source
Which of the following characteristic(s) may affect the accuracy of a noise level survey?
A.Wind blowing across the microphone B.Electric and magnetic fields
One method of assessing whether a specific hearing protection device has sufficient attenuation for the task at hand is to:
A.look at the NRR on the hearing protector package. B.estimate the Noise Reduction Rating needed. If subject fit data are not available, NIOSH recommends derating hearing protectors by a factor that corresponds to the available real-world data. Specifically, NIOSH recommends that the labeled NRRs be derated as follows: Earmuffs - Subtract 25% from the manufacturer's labeled NRR Formable earplugs - Subtract 50% from the manufacturer's labeled NRR All other earplugs - Subtract 70% from the manufacturers labeled NRR For example, measure noise exposure levels in dBC or dBA with a sound level meter or noise dosimeter. When the noise exposure level in dBC is known, the effective A-weighted noise level (ENL) is: ENL = dBC - derated NRR When the noise exposure level in dBA is known, the effective A-weighted noise level is: ENL = dBA - (derated NRR -7)
In the design of a noise reducing enclosure, all of the following characteristics are desired except:
Acoustical absorbing material outside the enclosure
The rule of thumb for predicting combined decibel readings from two separately measured noise sources, where the two sources differ by 3 decibels is which of the following?
Add 2；The rule of thumb for combining decibels where the two sources differ from 2-4 decibels is to add 2 to the higher decibel level.0 - 1 is add 3 to the higher2 - 4 is add 25 - 9 is add 110 or higher is add zero
In choosing a noise control barrier, which represents the best choice of design?
Air tight enclosure
When do employees have to be notified of potential exposure to noise?
Any exposure equal to or greater than 85 dBA/8 hours
What is the audible range for an average young person with unimpaired hearing?
Between 16 - 20,000 Hz
How are the frequency bands on an octave band analyzer expressed?
Center frequencies
Assume that you are using an octave band meter and measuring in the 2000 Hz band. What are the upper and lower cutoff frequencies for this band?
Center frequency * 根号(2) = upper cutoff2000 * 1.414 = 2828 HzCenter frequency/ 根号(2) = lower cutoff2000/1.414 = 1414 Hz
The part of the ear which contains the hair like cells that detect sounds is the:
Cochlea.
The correct term for hearing loss that can be induced by occupational exposure to noise is which of the following?
Conductive
Which of the following best describes the type of health hazard produced by noise?
Damage to the hair cells of inner ear
Vibration exposure is monitored by measuring all of the following except:
Decibels ;Vibration is most commonly reported in acceleration units in meters per second squared; frequency in Hz; and duration in hours/day. Because accelerometers measure in only one axis, the direction of the acceleration component is also monitored.
The noise reduction which may be attained with the installation of barriers is dependent on all of the factors listed below except:
Doubling rate
What is the most expedient method of protecting a worker from noise?
Ear protection
One of the problems with the old method of using cotton earplugs was the cerumen. Cerumen is also detrimental to some of the modern earplugs. What is cerumen?
Earwax
Two types of condenser microphones are commonly available. One is the air-dielectric condenser microphone. The other is the:
Electret.
Which of the following is true about the OSHA standard for a work area that has a noise level above 90 dB?
Employer must supply a few types of hearing protectors.
In worker's compensation cases involving hearing loss, the term low fence is often heard. Low fence varies by state. What is the meaning of this term?
Hearing threshold level at which impairment begins
If a man were exposed to 75 dB for years, what would his audiogram probably show at age 55?
Increasing losses with higher frequency
If a noise source is near the intersection of a wall and floor of a room so that 1/4 spherical radiation of the noise occurs, then Q =?
Q is a measure of the directivity of the sound.In a free field:Q = 1For hemispherical radiation:Q = 2For 1/4 spherical radiation:Q = 4
Numbness of the fingers is associated with:
Raynaud's Syndrome.
An employee works inside an enclosure placed around a noise source. Why is the sound pressure level experienced by the worker greater, than without the enclosure?
Reverberation
If an audiometric booth meets all but the 500 Hz criteria, what could this be attributed to?
Room noise
The Noise Insulation Factor (NIF) is used to estimate the relative noise insulation capability of a room. The unit for total room absorption (A) is the:
Sabin；The sabin is the unit for total room absorption. The formula for calculating the Noise Insulation Factor is:NIF = 10log (A/T) dBWhere:A = Total room absorptionT = Transmittance
Hearing loss attributed to listening to rock music loud traffic noise,I-Pods, fireworks on New Years Eve, etc is called: A.Psychogenic.
Sociocusis.
Which instrument is recommended by ANSI (or NIOSH) for checking audiometric booths?
Sound level meters with octave band filter sets
The ability to localize the direction from which sound waves are emanating is called:
Stereophony
If a worker has accumulated a noise dose of 91% (as calculated under OSHA's hearing conservation standard) then the equivalent TWA in dBA is equal to:
TWA = 16.61(log dose%/100) + 90Substituting we get:TWA = 16.61 (log 91/100) + 90TWA = 16.61 (-0.4096) + 90TWA = -0.6553 + 90= 89.3
A temporary depression of the hearing is called a:
Temporary Threshold Shift (TTS).
A sound level measurement of 100 dB is taken three feet from the source. What will the sound level be 12 feet from the source?
The formula for calculating sound level, based upon distance, is based on the inverse square law.LP2 = LP11 - 20 log r2/r1Where:LP2 = the sound level at distance r2LP1 = the measured sound at distance r1In this case:LP2=100 - 20 log 12/3 = 88 dB. A rule of thumb for calculating this is that each doubling of distance from the source results in -6 dB.
What is the threshold level for noise dosimeters?
The level at which the dosimeter can integrate noise into a measured exposure
At what frequency do the A, B, and C scales equal each other?
The response curves for the three scales listed all cross at 1000 Hz.
Sound pressure level is dependent on distance from the noise source. Sound power level Is not dependent on distance from the source.
The sound power level of a source is independent of the environment. However, the sound pressure level at some distance (r) from the source is dependent on that distance and the sound-absorbing characteristics of the environment. Sound power level is not dependent on the location of the device.
Ceramic microphones have good frequency response and are not affected significantly by changes in atmospheric humidity and temperature. They do have one of the following limitations:
Upper frequency limit is not as high as other types.
When does the employer need to administer an effective hearing conservation program according to OSHA regulations?
When the 8hr. TWA exceeds 85dB on the A scale
If an octave band spectrum increases 3dB per octave, what type of noise is probably present?
White noise
Conductive hearing loss, in contrast to sensorineural hearing loss, is least likely due to an interference with the conduction of sound in the:
cochlea.
As an IH you may need to appraise a noise hazard. You must consider that:
damage can occur slowly and without pain being noticed.
The least likely description of transmission loss (TL) is:
energy lost to the surroundings.
If sound pressure levels are measured using the A, B and C weighting scales and the differences are negligible, then the predominant frequencies of the sound are:
greater than 1000 Hz.
Raynaud's Syndrome is caused by:
hand-arm vibration.
Piezoelectric microphones have good frequency response and require no external voltage or current. One drawback to using piezoelectric microphones is that they are susceptible to high temperatures and:
humidity and aging.
When incurring a Temporary Threshold Shift (TTS) due to a noisy workplace, most of the TTS occurs:
in the first few hours of exposure.
Early hearing loss caused by noise:
is not generally noticeable to the person.
