Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
65 Cards in this Set
- Front
- Back
|
Sound
|
-Any pressure variation in air, water, or some other medium that the human ear can detect
-A longitudinal wave created by vibrating objects that spread from one location to another -Air molecules compress & expand to produce sound |
|
|
Noise
|
Unwanted sound
|
|
|
Velocity
|
The speed of sound; depends on density and temp
|
|
|
Wavelength
|
-Distance from one point of wave to the same point on the next wave
-Crest-to-crest or trough-to-trough -"The distance from one complete compression to another" |
|
|
Frequency
|
-How often a sound wave will repeat in a second
-Perceived as pitch |
|
|
Pure Tone
|
One single frequency
|
|
|
Complex Sound
|
Wide variety of different tones & amps mixed together
|
|
|
Octave Band
|
Range of frequences extending to exactly DOUBLE frequency
|
|
|
Units of Velocity
|
ft/sec
|
|
|
Units of wavelength
|
feet per cycle
|
|
|
Units of frequency
|
cycles per second (cps) or Hertz (Hz)
|
|
|
Sound Power
|
-Total amount of sound that a source produces
-Measured in Watts (W) -Never changes, no matter what the surroundings |
|
|
Sound Intensity
|
-Actual measured & reported sound characteristic
-The amount of sound power per unit area Units: W/m2 |
|
|
Sound Pressure
|
-Characteristic of Sound that is actually measured and reported when quantifying sound
-Difference between normal atmospheric pressure and actual pressure -units: N/m2 or Pascals (Pa) |
|
|
Sound Pressure Level
|
-What noise measurement instruments display in decibels (dB)
-Measured in N/m2 or Pa |
|
|
Decibel
|
-Unit of measurement of sound level
-Describes sound pressure level at a specified distance -dB |
|
|
Rule of Thumb for Quantifying Sound- Doubling Sound
|
Add 3dB to get new sound pressure level
|
|
|
Flat Response (dB flat)
|
-When no weighting is used
-Used for Octave Band analysis -Does not modify sound |
|
|
A Weighting
|
-Standard noise exposure
-Used by BE when assessing hazardous noise -Discriminates heavily against the lower frequencies -Can be automatically assumed to be used if no weighting is specified |
|
|
C Weighting
|
-Similar to flat response except at very low & very high levels
-Represents relative response of human hearing to high sound levels |
|
|
B Weighting
|
Type of weighting that is not normally used
|
|
|
Purpose of the HCP (Hearing Conservation Program)
|
To protect workers from harmful effects of hazardous noise
|
|
|
AFOSH Standard 48-20
|
Governs HCP and covers responsibilities, requirements, standards, protection, controls, & evals
|
|
|
29 CFR 1910.95
|
-Occupational Noise Exposure
-OSHA regulation |
|
|
Key Players in the HCP
|
-Aerospace Medical Squadron/Reserve Medical Unit Commander
-Wing & Base Ground Safety -Squadron Commanders & Workplace Supervisors -Public Health -Employees |
|
|
BE Role in HCP
|
*Conduct evaluations to identify workers potentially exposed to harmful noise levels:
-Perform surveys & dosimetry to quantify noise hazards -Complete OEHED data summary -Provide shop supervisors with results -Assess all controls & evaluate work areas -Approve HPDs -Assess engineering controls feasibility -Collect rosters of exposed personnel & share with PH -Conduct assessments |
|
|
Anatomy of the Ear
|
-External Ear Canal
-Semicircular canals -Auditory nerve -Eardrum -Middleear -Eustachian tube -Cochlea |
|
|
How sound is heard by the ear
|
1. Sound enters ear via external ear canal
2. Strikes eardrum 3. Vibration is passed to bones of middle ear 4. Vibration of bones stimulates cells & nerve endings in cochlea 5. Signal is sent along auditory nerve |
|
|
Auditory Effects of Noise Exposure
|
Hearing loss, Tinnitus, Acoustic Trauma
|
|
|
Hearing Loss
|
-Damage to the hair cells and degeneration of the nerve cells
-Can be temporary or permanent |
|
|
Tinnitus
|
A condition in which people perceive they hear sounds in one or both ears when there is actually no sound. It is usually temporary, but can become permanent.
|
|
|
Acoustic Trauma
|
Temporary or permanent hearing loss due to a sudden, extremely high intensity noise (i.e. explosion)
|
|
|
Non-Auditory Effects of Noise Exposure
|
Effects on job performance- decreased productivity, annoyance, interference, etc.
Effects on community relations- changes in property values, etc. |
|
|
Potential Hazardous Noise
|
Exposure to steady-state noise having an 8-hour TWA noise level greater than or equal to 85 dBA or exposure to impulse/impact noise levels greater than 140 dB peak SPL, regardless of duration
|
|
|
Potentially Hazardous Noise Area
|
Any area where personnel could be exposed to steady-state noise having an 8-hour TWA noise level greater than or equal to 85 dBA or exposure to impulse/impact noise levels greater than 140 dB peak SPL, regardless of duration
|
|
|
Community Noise
|
Consideration must be given to factors that interfere with human activities, including type of activity & attitudes
|
|
|
Criterion Level
|
-The sound level allowed for an 8-hour exposure used as the basis of a noise standard
-85 dB(A) for the USAF |
|
|
Exchange Rate (Doubling Rate)
|
The trade-off relationship between an increase (or decrease) in sound level & the corresponding change in allowed exposure duration
-For each doubling time, allowed noise level decreases by 3dB 1 hr=94 dBA 2 hr=91 dBA 4 hr=88dBA 8 hr=85 dBA 16 hr=82 dBA |
|
|
Hearing Noise Exposure Limits
|
85 dBA for 480 minutes (8 hrs)
94 dBA for 60 minutes (1 hr) 99 dBA for 19 minutes >115 dBA: NO unprotected exposure |
|
|
Whole Body Effects on Noise Exposure Limits
|
No octave or 1/3 octave band level may excees 145 dB for frequences from 1Hz-40kHz AND overall sound pressure level must be below 150 dB
|
|
|
Pregnant Workers Noise Exposure Limits
|
Use job rotation (do not work shifts in which hazardous noise is present) and avoid working where PPE is required
|
|
|
Job Performance Noise Exposure Limit: Quality person-to-person Normal Conversation Tone
|
70-80 dB(A)
|
|
|
Job Performance Noise Exposure Limit: Office Setting
|
above 65 dB(A); noisy, telephone use may be difficult
|
|
|
Job Performance Noise Exposure Limit: Group meeting/Study/Resting
|
34-45 dBA
|
|
|
Music Exposure Criteria for Employees and Customers
|
Employees: AFOSH limits apply
Customers: Should not exceed an equivalent continuous level of 94dBA for any continuous 2 hr period |
|
|
Factors to consider when evaluating Noise Sources/Areas
|
-Inventory noise producting equipment
-Complaints/Surveillance Data -Determine worker position & actions -List details describing the machinery or processes affecting the noise |
|
|
3 Survey Methods Used to Identify Hazardous Noise Sources & Areas
|
Noise Source Survey, Worker Exposure Survey, Hazardous Noise Area Survey
|
|
|
Noise Source Survey
|
-AFOSH Std 48-20, para 3.6.3.1
-Used to classify whether a particular noise source output exceeds the criterion level of 85 dB(A) & could present a potential exposure hazard to workers |
|
|
Worker Exposure Suvey
|
AFOSH Std 48-20 para 3.6.3.2
-Where the potential to exceed the limits in para 3.1 exists, worker exposures shall be evaluated by direct measurements with noise dosimeters, directly or indirectly with noise |
|
|
Hazardous Noise Survey
|
-AFOSH Std 48-20, para 3.6.3.3
-Used to define work areas where noise exposures are assumed hazardous based on routine operations |
|
|
Job Performance Noise Exposure Limit: Quality person-to-person Raised Conversation Tone
|
80-90dB(A)
|
|
|
Rule of Thumb for Quantifying Sound: Doubling the Distance
|
Double the distance from the source, and subtract 6dB from the pressure level (when halving the distance, add 6dB to pressure level)
|
|
|
Job Performance Noise Exposure Limit: Workplace
|
Above 90 dB(A); person-to-person communication difficult
|
|
|
Ways in Which Noise Travels
|
Direct and Reflected
|
|
|
Direct Path
|
Sound travels directly to ear from source to receiver; can be omnidirectional, in all directions, or path of least resistance
|
|
|
Reflected Path
|
Sound waves rebound from sources ("echo")
|
|
|
Engineering COntrols for Hazardous Noise at Source
|
Process Substitution, Product Substitution, Machine Treatments
|
|
|
Methods of Machine Treatments
|
3 methods:
-Reduce the Driving Force (1st and most direct method) ex: lubrication, replacing worn parts, reducing speed, cushioning, etc. -Isolate Responding Surface ex: machine guards/casings, etc. -Reduce Surface Response ex: increasing mass of surface |
|
|
Engineering Controls Controls for Hazardous Noise at Path
|
-Shields & Barriers
-Enclosures (partial or total: total is less noise, but can cause overheating of machinery) -Room Treatments: placing acoustically absorbent materials to walls |
|
|
Admin Controls for Hazardous Noise as applied to Path & Receiver
|
-Job Rotation
-Changes in Production Schedule -Preventative Maintenance -Time Limitations: decrease duration of exposure -Labeling -Training -"Buy-Quiet Program": purchasing quieter equipment, can be considered Engineering Controls |
|
|
Labeling Requirements for Hazardous Noise Areas
|
-areas at or above 85dBA need: CAUTION: HAZARDOUS NOISE: HEARING PROTECTION REQUIRED
-BE will specify exact wording for any extra verbage for signs |
|
|
Labeling Requirements for Hazardous Noise Equipments
|
Each tool producing greater than or equal to 85 dBA will have labels on them (Exception: when an entire area is hazardous & equipment is stationary)
|
|
|
Range of Frequencies Most People can Hear
|
20-20,000 Hz
|
|
|
High Frequency Noise
|
>500 Hz
|
|
|
Low Frequency Noise
|
<500 Hz
|
