Occupational Health & Safety Management
HRM 3400 – Winter 2012 – Anna Blake
Lecture 3 – Physical Agents – Jan 23
- The basis of operations and existence depends on the principles of physics.
- Types of energy defined by distance, mass, and/or time.
- Most health effects are chronic in nature; resulting damage can take years to
Types of Physical Agents
o Ambient – ‘all around us’.
o WSIB statistics regarding hearing loss.
1 million in compensation cost between 1995 and 2004.
o Defined as ‘unwanted sound’
Sound is defined as ‘the auditory sensation evoked by the
oscillations in pressure in a medium with elasticity and viscosity.’
o Travels through air in a wave pattern called a sine wave.
Wavelength – the distance that one complete sine wave cycle will
Number of time/second that a complete sine wave is repeated.
Expressed in units of Hertz (Hz) or cycles/sec.
The lower the sound (pitch) the lower the frequency.
Range that the human ear can hear is 20 to 20,000 Hz.
o The oscillating motion of a particle or body moving about a reference
position. Wave form similar to ‘sound wave’.
- Thermal stress (heat and cold)
o Involves cold and hot temperature extremes.
o Results in the body not being in homeostasis.
o Homeostasis = balance of heat generation.
- Radiation (ionizing and non-ionizing)
Human Hearing Response
- Threshold of hearing
o Envelop or range of sound that the human ear can perceive or hear.
- Measurement of noise uses the decibel (dB) (logarithmic scale).
o A unit of measure of sound pressure level that is equal to 20 times the
logarithm to the base 10 of the ratio of the pressure of sound, divided by
the reference pressure of 20 micropascals.
- Represented as a response curve A-weighted curve (dBA). - dBA
o Means a measure of sound level in decibels using a reference sound
pressure of 20 micropascals when measured on the A-weighting network
of a sound level meter.
- Three characteristics
Most sounds are made up of different frequencies.
Sound of one frequency = pure tone.
o Duration (length of exposure)
Continuous, impulse (impact)
o Loudness (amplitude)
Anatomy of the Ear
- The inner ear is contained in the bony, or osseous, labyrinth within the temporal
bone. The stirrup is in contact with the round window. The osseous labyrinth is
filled with perilymph (liquid).
- Each of the receptor organs of the inner ear are supplied nerve fibers of the
eighth (acoustic) nerve.
Noise Exposure Limits in Ontario
- Changes came into effect July 1, 2007.
- Section 139 of the Industrial Establishment regulation is changed to include:
o Equivalent sound pressure level of 85dBA.
o Equivalent sound pressure level
The steady sound level in dBA which, if present in a workplace for 8
hours in a day, would contain the same total energy as that
generated by the actual and varying sound levels to which a worker
is exposed in his or her total workday.
Workplace Noise Measurement
- Octave band
o The interval between two sounds eight full tones apart.
o The higher tone has double the number of vibrations/second and double
o Octave band analyzer used to characterize workplace noise in order to
determine control measures.
Permits analysis of sound at specific frequencies.
- Part of a hearing conversation program.
- Audiometer – an instrument used to determine the sensitivity of a person’s
hearing or degree of hearing loss.
- Pre-employment baseline.
o Usually within 6 months of hire.
- Annual - Follow-up
Causes of Hearing Loss
- Chemical exposure.
- Noise induced hearing loss.
o Workplace exposure.
o Non-work related.
- Birth defect.
Types of Hearing Loss
- Noise can affect humans in three ways.
Loss of hearing
• Conductive (bone conduction)
o Caused by trauma, infection, or hereditary.
o Higher frequency affected first.
• Cardiovascular (vasoconstriction), neurological (headaches),
endocrine changes (changes in hormonal secretions),
disturbances in equilibrium.
- The record of a given individual’s hearing sensitivity. An audiogram shows
hearing threshold level measured in decibels as a function of frequency
measured in hertz.
o Noise baffles – sound absorbing material.
o Placing vibrating pads under machinery.
o Providing barriers (separate room).
o Hearing protectors (PPE).
- Note changes to industrial regs s.139
o Protective measures shall include the provision and use of engineering
controls, work practices and personal protective equipment.
o PPE allowed only if other controls not obtainable or practical. Ten Decision Factors of Hearing Protectors
- Ease of donning
- Effective attenuation (NRR)
- Useful life
Causes of Vibration
- Dynamic effect of machine tolerances, clearances, rolling, rubbing contact.
- Out of balance conditions.
- Can be accidental or intentional.
Health Effects – Vibration