Units 6 And 2 Flashcards
(39 cards)
What is 0 DB and 130 commonly known in thresholds
Why can’t noise sources be added together ?
0 db threshold of noise
130 db is threshold of pain
Because intensity levels are given on a logarithmic scale. and it measures pressure. You can’t simply add the figures together as 90db + 90db 180
Would cause instant deafness. You calculate an a combined dose if the sources are the same by adding three 90 + 90 = 93db which equates to the doubling of the sound.
Explain
Noise
Amplitude
Frequency
Noise is any unwanted sound
Amplitude is the intensity of the sound measures in DB
Frequency is the pitch measured in Hz
What is the A weighted scale?
A A weighted scale electronically assimilates sound pressure and mimics the human ears response across frequencies. This measurement of DB is a good indicates of the physical damage caused to hearing.
Describe how the ear converts sound to the brain
The ear transmits nerve impulses to the brain by detecting mechanical vibrations through the outer, middle and inner ear
Explain how the damaging effects of noise are related to the dose the ear recieves
The dose received the ear depends the level of noise and the duration of exposure. Short exposure to high levels is comparable to long exposure of low noise. Same damage is caused.
What is sensorineural and conductive hearing loss and what is the practitioner concerned with ?
Sensorium when the hairs in the cochlea are damaged, mainly to excessive occupational noise.
Conductive breakdown of the conductive mechanism of the ear, acute trauma explosion or gun shot
Explain threshold shift
A threshold shift is a reduction in a persons ability to hear, they need more sound intensity to stimulate the ear. Temp or permanent
Factors affecting audiometry
Technical limitations how accurately can the hearing be detected ?
Learning effect
Headphone fit
What is the hse 5 step to noise risk assessment ? L108
Is the a risk due to noise
Use noise data and manufacturers guidelines
Decide who can be harmed and how
Consider all workers not just the operators
Evaluate the risks and decide/ implement controls Average noise exposure levels Times of day Tasks Patterns of work Duration of exposure
Record your findings
Ra and action plan
Review your findings
Changes, no longer valid or date
What considerations need to be considered when panning a noise survey
Who
Is affected
All that are exposed to the lower action value
Where
Every location a person walks through or spends time in
How
Take a measurement at the position occupied by the operators head
For how long
Measurements need to be sufficient to account for variations in the day.
Group sampling
Several workers in the same area
Mobile workers
Very short duration
Gunfire
Second more detailed survey
If the upper action value is exceeded in a location
4 measuring devices for noise
Basic sound level meter
For a short spot check (does not conform with cnar regs)
Islm integrated sound level meter Complies with cnar class 2 instrument Measures a and c weighting
Personal dosimeters
Worn by the person, small and records time and intensity of exposure
What are the lower and upper action noise level values for noise and what must be done at each level
The lower exposure and upper exposure action values are A weighted measures
80 db lower (A) 135 (C) peak sound pressure levels
At this level or up to the upper
IITs on risks of noise
Ear protection available bit not enforced
Health surveillance
85 upper (A) and 137 (C)
Ear defenders are last resort, noise must be reduced alarp
Designate hearing zones
Ensure hearing protection is worn and provided
Health surveillance
What is the Hierarchy of noise control ?
RAC.
Reduce noise at source
Change the source, relocate the source, re design the source, maintenance
Reduce sfarp below upper and ideally below lower value
Attenuate noise transmission Reduce transmission before it reaches the worker Isolate source - anti vibration mounts Acoustic barriers Acoustic enclosures
Control noise exposure at receiver Acoustic havens Hearing zones Passive and active hearing pro Limit exposure time HS audiometry
What are the three noise pathways ?
What are the three ways of reducing noise ?
Directly
Direct from the source to the person
Reflected
Some is reflected off surfaces
Transmitted
Some is transmitted through materials
Noise reduction at source
Attenuation in transmission
Control at the reciver
What are different types of ear protection ?
Ear plugs
Ear defenders
Noise cancelling headphones
What is meant by vibration dose
The amount of damage done by vibration is dependant upon the dose of vibration energy received.
A given dose of vibration energy will cause an equivalent degree of harm. The dose is determine by:-
Magnitude of vibration (rms) acceleration
Duration of exposure
Give the range of effects vibration can have on the body.
When a person grips a particular object that vibrates, that vibration is transmitted through the hand and into the body. This is commonly known as HAVs. It effects the nerves, the muscles and the circulation.
Whole body vibration:- can be felt when the body is supported on a vibrating surface eg transport effects are principally back pain.
Describe the condition of vibration induced white finger
Early stages vibration causes numbness and slight tingling in the fingers. With further exposure the tips of one or more fingers suffer blanching, and this will continue to the base of the finger with further exposure. After about an hour the fingers become flushed and is accompanied by considerable pain.
There is reduced sensitivity to temperature, pressure, pain and less manipulative ability.
List workers associated with HAV
Percussive metal work tools
Rotary tools and grinders
Percussive hammers and drills
Chainsaws
Which workers may be effected by WBV
Drivers of heavy vehicles/ operators heavy machines, FLT’s, aircraft. People operating vehicles over rough terrain.
What is CVAR 2005 definition of HAV
And whole body vibration
Mechanical vibration transmitted into the hands and arms during a work activity
Mechanical vibration transmitted into the body, when seated or standing, through the supporting surface during work activities
Briefly explain
Amplitude
Frequency
Acceleration
Vibration magnitude
Vibration Direction
Amp
The distance i metres from the point of rest to the point of maximum displacement in either direction
Frequency
Cycles per second in Hz
Acceleration
The rate of change of velocity of a vibrating object (m/s 2) measuring vibration magnitude
Vibration magnitude
Vibration magnitude is expressed in terms of acceleration.
Vibration direction
With complex vibrating objects there may be displacement in all three dimension xyz
Adding these dimensions together contribute to the overall vibration recieved by hand and body
What is the daily dose received by a worker expressed as
The dose is determined the magnitude of vibration and the duration of exposure.
The eight hour energy equivalent vibration magnitude or A (8)
CVR equations in regs
HSE calculator
Hse ready reckoner
What is the five step approach to vibration risk assessment
Look to see wether vibration exposure might be a problem that needs to be managed and identify likely havs and WBV exposure
Identify all workers at risk
Evaluate the risks and decide on controls to comply with the regs
Record your findings
Review your findings
