听力保护培训计划培训ppt课件.pptVIP

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 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 HEARING ORGAN 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. 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 ) Speech/communication ( 300 - 3000 Hz ) Noise spectrum ( Figure 1 ) The factors that influence the effect of noise on human …...... 4 factors influence the effect of noise to human. The frequency of noise : Higher frequency is more dangerous than lower frequency Noise intensity : Higher intensity is more destructive than the