文档介绍:Hearing Conservation Training program
Dr Mohamad Sabri Mohd Shaffi
Principle of sound and hearing mechanism.
Effect of noise on human
Law related to Hearing Protection
Audiometric Test
Hearing Protective Devices
CONTENTS
sound
The changes of pressure in a specific medium which is detected by the ears
Sound waves cannot pass through vacuum.
Definition
HERTZ ( Hz ) = unit for frequency Bass : 500 Hz Treble : 3000 Hz Human hearing Frequency : 20-16000Hz Human speech / communication : 300 - 3000 Hz
DECIBEL ( dBA ) = measurement of intensity 0 dBA : lowest intensity heard 140 dBA : Threshold of pain
Principle of Sound
The sound energy is produce by vibration of the medium
Moves through a medium and can be heard
The speed and distance depend on the density of medium
Sound cannot pass through vacuum
Various speed through a medium : a. Air - 340 meter per second. b. Water - 1500 meter per second. c. Metal - 5000 meter per second.
THE UNWANTED SOUND
NOISE
AN & MECHANISM
Structure of the ear : a. Outer ear b. Middle ear c. Inner ear
Parts of the ear: Outer ear : Pinna, Auditory canal Middle ear : Ossicle bone Eustachian tube Inner ear : Oval window, semicircular canal, cochlea & auditory nerves.
STRUCTURE OF THE EAR
THE EFFECT OF NOISE……...
Classification of sound according to the frequency :- i. Infrasonic ( 0 - 20 Hz ) ii. Human ability to hear ( 20 - 16000 Hz ) iii. Ultrasonic ( more than 16000 Hz )
munication ( 300 - 3000 Hz )
Noise spectrum ( Figure 1 )
The factors that influence the effect of noise on human …......