Noise Flashcards
What is noise?
Undesirable or unwanted sound
Subjective
What is noise propagation?
Generated at a source and spreads spherically away from that source
Diminished with distance and loses engery
What occurs as “sounds waves” when objects are encountered?
Bending and diffraction
How is sound measured logarithmically?
bel (B)
What is the more commonly used subunit for sound?
Decibel (dB)
1/10 bel
The power of a sound wave is proportional to the…..
Square of the pressure
Combinations of sounds may make ____ in the decibels.
Little
At what level would a person receive painless damage?
85-125 dB
At what level would a person start to feel pain?
Over 125 dB
Frequency
Vibrating object moves molecules back and forth causing sound waves to move outward
What is the range of normal hearing?
20 Hz to 20 kHz
Steady frequencies
Pure tones
Tuning forks and electronic oscillators Uncommon
Intensity
Directly proportional to sound pressure
Pascals (Pa) and micropascals (uPa)
What is the normal range for intensity?
20 uPa to 20 Pa
What is the A scale?
Sound measurement as an approximation of the sensitivity of the human ear
2 sounds with the pressure lvl may have different A levels
Steady noises
Continuous, intermittent, impulse
What are the effects of noise to the outer ear?
Minimal direct effects, possible physical damage to pinna or ear with small effects
Restriction of ear canal with cerumen causing mild to moderate hearing loss
What are the effects of noise to the middle ear?
Effects due to the acoustic reflex of involuntary contractions in the ossicular chain due to high-intensity sound
Overtime stiffening of the chain impairing low frequency sounds
What can occur if there is fluid in the middle ear and what else could cause this?
May produce mild to moderately severe hearing loss
Perforated ear drum
Fixed or disconnected ossicles
What are the effects of noise to the inner ear ?
Sensorineural
Exposure to loud noise may produce temporary threshold shifts (may become permanent)
Intense bursts may cause permanent damage immediately
Describe the cochlea.
Hair cells that change mechanical fluid vibrations into nerve impulses
Base: high frequencies
Apex: low frequencies
Inner hair: all sounds
Presbycusis
Slow loss of hearing due to age
What are some causes of age-related hearing loss?
Familial, repeated exposure to loud noises, smoking, medical conditions or medications
What are the symptoms of age-related hearing loss?
Sounds may seem overly loud
Difficulty hearing things in noisy areas
HIgh pitches sounds like s or th may be hard to distinguish
Men’s voices easier to hear, some people sound slurred
Tinnitus
What are some steps to help age-related hearings loss?
No cure
Hearing aids
Telephone amplifiers and other assertive devices
Sign language or speech reading
Describe a cochlear implant.
Must have a functioning auditory nerve
Restores a sense of hearing, not actual ability to hear
Makes sounds louder
Should be considered in those with relatively short-term total hearing loss
What are some other effects of noise?
Reduced ability to communicate, in BP, changes in hormone production, sleep disturbances, behavioral changes, dec task performance
What are some way transport sources help control “environmental” noises of cars?
Noise barriers around road, sleep limits, highway surface texture, vehicle limits, tire design
What are some way transport sources help control “environmental” noises of aircrafts?
Engine design, sound attenuation packages, alteration of flight path direction and timing
Occupational noise has more…
Specific data and methods of control
What are the OSHA standards?
85 dB = 8 hr time weighted average (TWA)
Each 4 dB rise dec time exposed by half;
85 db = 8 hrs
89 db = 4 hrs
What scale does OSHA use for noise monitoring?
A scale
When should a person wear hearing protectors?
Over 85 dB or impulse noise over 140 dB
Double protection needed at 108 dB
