Noise Standard & Engineering Controls
Ultrasonic noise
- Frequencies higher than audible range - Ultrasonic cleaners
Infrasonic noise
- Intense low frequency noise - Air conditioning systems - Wind turbines
OSHA's recommendation for walk around noise survey
1) Tour the facility with somebody knowledgeable about operations 2) Note if it is necessary to speak loudly 3) Measure noise levels using SLM 4) Estimate worker exposure 5) Perform detailed noise monitoring if results suggest TWA > 80 dBA
The amount of noise exposure experienced by the worker
Definition of noise dose
4 dB
DoD exchange rate
Sound level meter
Documents noise levels from specific sources or machines
85 dBA or 90 dBA
Dosimeter criterion exposure level
3 dB or 5 dB
Dosimeter exchange rates
A or C
Dosimeter frequency weighting
Slow or fast
Dosimeter responses
Noise control engineers; workers; industrial hygienists; facilities managers; manufacturers
Examples of people responsible for a successful noise control program
An increase in dB exposure levels that requires the halving of exposure time or a decrease in dB exposure levels that allows doubling of the exposure time
Exchange rate
(# hrs of actual exposure/# hrs allowed by OSHA) * 100
Formula for noise dose
Type II SLM
General purpose measurements (accuracy of +/- 2 dB)
- Eliminate noise - Replace noise source with quieter equipment - Engineering controls - Administrative controls - Hearing protection devices
How do you reduce hazard from noise?
Engineering controls
Isolate people from the hazard
Type 0 SLM
Laboratory standard
1) Noise monitoring 2) Engineering and Administrative controls 3) HPDs 4) Employee Training 5) Monitor Hearing 6) Record Keeping 7) Evaluate Program
Mention OSHA's hearing conservation program elements
NIOSH: 3 dB DoD: 4 dB OSHA: 5 dB
Mention the exchange rates per agency
Area noise monitoring; personal noise monitoring
Mention the types of monitoring
3 dB
NIOSH exchange rate
A typical work setting
Noise sampling is representative of what?
Borderline hazards to susceptible ears
OSHA Hearing Conservation Amendment (1983) for TWA = 85 dBA
No significant risk to hearing
OSHA Hearing Conservation Amendment (1983) for TWA ≤ 85 dBA
Definite damage to all ears
OSHA Hearing Conservation Amendment (1983) for TWA ≥ 90 dBA
85 dBA
OSHA action level
5 dB
OSHA exchange rate
90 dBA
OSHA permisible level
Elimination
Physically remove the hazard
Type I SLM
Precision measurements in the field (accuracy of +/- 1 dB)
PPE
Protect the worker with Personal Protective Equipment
Ultrasonic cleaner
Provide an example of ultrasonic noise
Air conditioning noises and wind turbines
Provide examples of infrasonic noises
Substitution
Replace the hazard
Noise dose
The amount of noise exposure experienced by the worker
Meter can closely follow fluctuations in noise
Time constant SLM setting: Fast
Monitor transient sounds
Time constant SLM setting: Impulse/Peak
Easier averaging of fluctuations; smoother response
Time constant SLM setting: Slow
Fast; Slow; Impulse/Peak
Time constants of SLM
Area noise monitoring and personal noise monitoring
Types of noise sampling monitoring
Octave Band Analyzer
Typically integrated into Type 0 or Type I SLM
Most commonly used; mimics response of human ear
Weighting SLM setting: A
Use for impulse noise measurements
Weighting SLM setting: C
No weighting; used for octave band analysis
Weighting SLM setting: Z
100%
What % of noise dose is considered dangerous?
Based on data from lab and field studies; it looks to preserve hearing at 500, 1000, and 2000 Hz; cost of noise control; practical feasibility of implementation; OSHA standard was formulated to minimize, not eliminate the risk of hearing loss
What are factors in determining criterion level?
- Reports of diminished hearing following shift - Reports of tinnitus following shift - Reports that sounds are too loud - Difficulty with carrying out conversations - Noticeably loud emissions from equipment - Informal noise measures suggest potentially hazardous noise
What are indications of potentially hazardous noise
Time constant and weighting
What are the SLM settings?
Response, frequency weighting, exchange rate, criterion exposure level
What are the parameters for the dosimeter?
250 Hz & 1000 Hz
What are the test frequencies in the acoustic calibrator?
94 dB SPL and 114 dB SPL
What are the test levels in the acoustic calibrator?
Individual noise exposure levels
What can you estimate with area noise monitoring?
Temporal pattern, level of noise, frequency content of the noise, duration of exposure
What do we analyze when measuring noise?
Permisible exposure limit (PEL)
What does criterion level equal to?
The different noise levels and durations and then it averages together the level and duration of a workday to five a single number rating
What does the TWA take into consideration and what does it do with it?
Use SLM, several measurements are taken at different locations, and document measurements on a floorpan
What equipment do you use for area noise monitoring, where do you take the measurement, and how do you document it?
Use sound level meter
What equipment do you use for area noise monitoring?
Use dosimeter
What equipment do you use for personal noise monitoring?
Noise level (dBA) and time
What factors does the criterion level rely on?
They are more conservative
What happens with lower exchange rates?
85 dBA for 8 hours
What is NOISH's criterion level?
90 dBA for 8 hours
What is OSHA's criterion level?
140 dBA
What is OSHA's limit for impulse noise?
Intense low frequency noise
What is an infrasonic noise?
Frequencies higher than audible range
What is an ultrasonic noise?
Data from laboratory and field study
What is criterion level based on?
Exposure level which requires HPDs, monitoring of hearing, and investigation of feasible controls; constant sound level in dB that will result in 100% noise dose
What is criterion level?
Check calibration of SLM and dosimeter
What is the acoustic calibrator used for?
Employees with the same noise dose have the same risk of developing the noise induced permanent threshold shift (NIPTS) ignoring individual susceptibility
What is the clinical significance for noise dose?
Preserving hearing at 500, 1000, and 2000 Hz
What is the goal of criterion level?
Measure noise levels in different frequency bands
What is the goal of the octave band analyzer?
1) Elimination 2) Substitution 3) Engineering controls 4) Administrative controls 5) PPE
What is the order of the hierarchy of controls form most effective to least effective?
- Determine if noise levels are hazardous - Identify specific hazardous areas - Identify specific at-risk workers - Determine if a hearing conservation program is needed - Monitor changes
What is the purpose of conducting noise measurements?
Evaluate area noise levels
What is the purpose of the SLM?
Continuously monitor, integrate, and record the noise to calculate the dose
What is the purpose of the dosimeter?
The noise source
What is the target of engineering controls?
Calculation of the overall noise level
What is the time weighted average (TWA)?
An initial, "informal" survey used to observe work processes and machines to identify if formal noise monitoring is necessary
What is the walk around noise survey?
Noises with high variation
What noises are particularly dangerous?
Slow for time constant and A for weighting
What settings are most commonly used in the SLM?
Perform multiple measurements
What should you do if noise exposures vary throughout the day or production during a noise sampling?
Calibrate your equipment and document it and instruct your workers
What should you do prior to noise measurements?
Short duration, high level noise
What type of noise can cause greater variability in hearing loss?
Any modification or replacement of equipment to reduce noise levels by changing the noise transmission path
What will engineering controls do to the noise source?
When noise exposure varies
When is TWA beneficial to use?
When noise levels are relatively constant and when workers do not change location frequently
When is area noise monitoring beneficial?
Before and after noise measurement
When is calibration checked?
When noise levels fluctuate over time and when worker moves to several locations
When is personal noise monitoring beneficial?
- At the time of implementation of noisy operations - When new employees are hired - Within 3 months of any alterations that affect noise levels - When threshold shift are apparent in workers - At least once every 2 years where noise exceeds 95 dBA - At least once every 5 years where noise is less than 65 dBA
When to perform noise measurements?
Employer responsible for administering and continuing an effective conservation program
Who is responsible for a successful noise control program?
To establish a monitoring protocol for the workplace
Why do you need to take a noise sampling?
The cost will vary and purchasing new production equip is typically cheaper than retrofitting existing equip with noise controls
Why is economic feasibility of engineering controls an important factor in deciding whether to implement specific controls?
This may impact the type of recommended hearing protection and the type of noise control that is implemented
Why is it important to understand frequency characteristics of noise?
Administrative controls
Change the way people work
Dosimeter
Allows measurement of personal noise dose/exposure for a worker
- Inform about equipment, procedures, purpose - Workers should perform their tasks in a typical manner - Do not make unusual noises - Do not remove dosimeter - Avoid bumping or dropping dosimeter
Before noise measurement, what do you have to instruct the workers on?
