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Lesson 2: CAUSES OF HEARING DAMAGE
ARC 507: ENVIRONMENTAL CONTROL III
(ACOUSTICS AND NOISE CONTROL)
Department of architecture
Federal university of technology, akure
ARC 507: Environmental Control III (Acoustics and Noise Control)
Department of Architecture, Federal University of Technology, Akure, Nigeria
Contents
1. Introduction.
2. Noise Induced Hearing Damage.
Acoustic Trauma
Temporary Threshold Shift
Permanent Threshold Shift
Biologic Variability
Tinnitus
3. Other Causes of Hearing Loss
Ototoxic Agents
Diseases
Ageing
Socioacusis
ARC 507: Environmental Control III (Acoustics and Noise Control)
Department of Architecture, Federal University of Technology, Akure, Nigeria
SUMMARY
This topic explains the main adverse health
effects of noise: damage to the hearing
mechanism, known as noise– induced hearing
loss (NIHL); and tinnitus.
Also covered are other agents that can damage
hearing: ototoxic substances; diseases; and the
ageing process.
ARC 507: Environmental Control III (Acoustics and Noise Control)
Department of Architecture, Federal University of Technology, Akure, Nigeria
agents of hearing damage
Hearing damage may result from several agents –
both occupational and non – occupational:
• Noise – occupational (called occupational noiseinduced hearing loss).
•Noise–non – occupational (called Sociocusis)
• Ageing – (Presbyacusis).
• Diseases and infections (collectively called
Nosoacusis).
• Ototoxic hazardous substances in the work
place.
ARC 507: Environmental Control III (Acoustics and Noise Control)
Department of Architecture, Federal University of Technology, Akure, Nigeria
NOISE – INDUCED HEARING DAMAGE
Noise can affect hearing in four main ways:
• Acoustic trauma
•Temporary threshold shift (TTS)
• Permanent threshold shift (PTS)
• Tinnitus
ARC 507: Environmental Control III (Acoustics and Noise Control)
Department of Architecture, Federal University of Technology, Akure, Nigeria
NOISE – INDUCED HEARING DAMAGE
Acoustic Trauma
It is defined as damage to the ear resulting from a
single exposure or relatively few exposures to a very
intense level of sound (peak level greater than 140150 dB), usually impulsive in nature, e.g. explosions.
Acoustic trauma may cause:
• damage to the eardrum;
• damage to the ossicles; and
• mechanical damage to the hair cells.
ARC 507: Environmental Control III (Acoustics and Noise Control)
Department of Architecture, Federal University of Technology, Akure, Nigeria
NOISE – INDUCED HEARING DAMAGE
Temporary Threshold Shift (TTS)
It is defined as a temporary change in hearing level
that recovers between exposures, resulting from
sound levels over about 70 - 75dB(A).
ARC 507: Environmental Control III (Acoustics and Noise Control)
Department of Architecture, Federal University of Technology, Akure, Nigeria
NOISE – INDUCED HEARING DAMAGE
Growth and Recovery of TTS
ARC 507: Environmental Control III (Acoustics and Noise Control)
Department of Architecture, Federal University of Technology, Akure, Nigeria
NOISE – INDUCED HEARING DAMAGE
TTS for Different Noise level
ARC 507: Environmental Control III (Acoustics and Noise Control)
Department of Architecture, Federal University of Technology, Akure, Nigeria
NOISE – INDUCED HEARING DAMAGE
Permanent Threshold Shift (PTS)
This is permanent damage to the ear as a result of
continued or repeated exposure to excessive noise
over a period of time.
ARC 507: Environmental Control III (Acoustics and Noise Control)
Department of Architecture, Federal University of Technology, Akure, Nigeria
NOISE – INDUCED HEARING DAMAGE
Progression of NIPTS for 90 and 100db(A)
ARC 507: Environmental Control III (Acoustics and Noise Control)
Department of Architecture, Federal University of Technology, Akure, Nigeria
NOISE – INDUCED HEARING DAMAGE
Tinnitus
This is the term given to noises which are heard in
the ears’ or ‘in the head’ – ringing, buzzing, hissing,
whistling, pulsing or other sounds which do not
come from an external source
ARC 507: Environmental Control III (Acoustics and Noise Control)
Department of Architecture, Federal University of Technology, Akure, Nigeria
OTHER CAUSES OF HEARING LOSS
Ototoxic Agents
This means ‘toxic to the ear’.
Certain medications or chemical agents in the
workplace can damage the ear cells in the inner ear.
Over 200 agents have been reported as ototoxic.
These include:
• antibiotics such as streptomycin;
• quinine; and
• salicylates such as aspirin.
ARC 507: Environmental Control III (Acoustics and Noise Control)
Department of Architecture, Federal University of Technology, Akure, Nigeria
OTHER CAUSES OF HEARING LOSS
Ototoxic Agents continues...
Workplace ototoxic agents include:
• solvents such as benzene, toluene, butanol,
trichloroethylene; and
• arsenic, lead, cobalt, mercury, and lithium.
ARC 507: Environmental Control III (Acoustics and Noise Control)
Department of Architecture, Federal University of Technology, Akure, Nigeria
OTHER CAUSES OF HEARING LOSS
Diseases
Nosoacusis is defined as hearing damage resulting
from diseases and infections, ototoxic medications,
or trauma (blows) to the head.
Many systemic and hereditary diseases can cause
hearing loss. Among these are: rubella, meningitis,
diabetes, renal disease, rheumatoid arthritis and
Meniere's disease.
ARC 507: Environmental Control III (Acoustics and Noise Control)
Department of Architecture, Federal University of Technology, Akure, Nigeria
OTHER CAUSES OF HEARING LOSS
Ageing
Presbyacusis is defined as progressive loss in
sensitivity at the high frequencies occurring with
increasing age.
A series of changes occur in the auditory system as
humans age. These include:
• loss of hair cell.
• degeneration of the stria vascularis.
•loss of spiral ganglion cells in the auditory nerve.
• degenerative changes in the central auditory
nervous system.
ARC 507: Environmental Control III (Acoustics and Noise Control)
Department of Architecture, Federal University of Technology, Akure, Nigeria
OTHER CAUSES OF HEARING LOSS
Median audiogram for male
ARC 507: Environmental Control III (Acoustics and Noise Control)
Department of Architecture, Federal University of Technology, Akure, Nigeria
OTHER CAUSES OF HEARING LOSS
Median audiogram for female
ARC 507: Environmental Control III (Acoustics and Noise Control)
Department of Architecture, Federal University of Technology, Akure, Nigeria
OTHER CAUSES OF HEARING LOSS
Sociocusis
This is defined as noise – induced hearing loss
from non-occupational noise, for example, high
level music, recreational shooting, and other noisy
hobbies such as carpentry and drag racing.
ARC 507: Environmental Control III (Acoustics and Noise Control)
Department of Architecture, Federal University of Technology, Akure, Nigeria