Noise and Vibration کلیه مطالب بهداشت حرفه ای در
Some Stats…. Approx. 30million people are exposed to hazardous noise through work (OSHA). Every year, nearly 10m people develop noise-induced hearing loss due to occupational exposures (NIOSH). Approx. 2m people are exposed to occupational vibration in the United States (NIOSH, 1998).
Sound is vibration. Can you see sound? How do we know it’s there?
Let’s feel it! Vocal chords Drum We can hear and feel vibration.
What is vibration? Vibration is something that moves back and forth very fast.
Tuning Fork In Water How do we know the tuning fork is vibrating? –Can we see it? –Can we hear it? What will happen when we put it in water? –Can we see it? –Can we hear it? –What happened?
Sound Moves in Waves. What does a wave look like on the ocean? Sound waves are similar. Side View: http://members.aol.com/nicholashl/waves/movingwaves.html http://members.aol.com/nicholashl/waves/movingwaves.html Top View: http://members.aol.com/nicholashl/waves/circularwaves.html http://members.aol.com/nicholashl/waves/circularwaves.html
Sound can be loud and soft. What’s the difference? Loud sound wave Soft sound wave They are taller. They are shorter.
Sound can move fast and slow. Fast sound waveSlow sound wave Sound is measured by vibrations per second. This is called frequency. It’s measurement tool is called Hertz. (HZ) Tuning Fork A : 440 HZ Middle C on the Keyboard: 261 HZ
So, fast and slow vibrations make different high and low sounds. We call that pitch. High pitch has fast vibration or high frequency. Low pitch has slow vibration or lower frequency.
Let’s check what you know! Sound is ________________. Sound moves in ____________. Sound can be ___________. Sound can be ____________. We measure loudness by ________. Highness and lowness of sound is ______________. The speed of the vibrations is called _______________. Waves Vibration Fast and slow Loud and soft Frequency Decibels Pitch
Sound can reflect. Hard surface http://members.aol.com/nicholashl/waves/reflection1.html
String Instruments Tighter the string – higher the sound. Looser the string – lower the sound. Shorter the string – higher the sound. Longer the string – lower the sound.
String instruments need a sound box or amplifier. These are usually made of wood. The amplifier needs a sound hole for the sound waves to escape.
Wind Instruments Shorter the pipe – higher the sound. Longer the pipe – lower the sound. Example: recorder, slide whistle, bottles Faster the air speed – higher the sound. Slower the air speed – lower the sound.
Horn is Born. Ancient horns were made from large shells. Then horns were made from metal and were long and straight. Man learned how to bend metal and curve the tubes He later put valves and keys on them to make more sound changes.
Percussion Instruments Bigger the instrument – lower the sound. Smaller the instrument – higher the sound. Tighter the membrane – higher the sound. Looser the membrane – lower the sound.
Health Effects of Noise Physiological Effects –Hearing Loss –Quickened Pulse –Increased BP –Constriction of Blood Vessels –Fatigue Psychological Effects –Stress –Performance Reduction –Annoyance and Adverse Social Behavior
Critical Noise Risk Factors Frequency Sound Pressure - Intensity Sound Power Time Distribution –Continuous Noise –Intermittent Noise –Impulse Noise
OSHA Standards - Noise 1.Monitor Noise Levels 2.Medical Surveillance 3.Noise Controls 4.Personal Protection 5.Education and Training
Methods of Noise Control 1.Plant Planning Checking noise specifications Designing Plant layout Using the right materials Isolating/shielding sound sources 2.Substitution Using quieter equipment Using quieter processes Using quieter materials
Vibration What is Vibration? Types of Vibration Exposures: –Hand-arm Vibration Exposure –Whole-boy Vibration Exposure
Sources of Vibration 1.Segmental (Hand – arm) Powered Hand Tools Leaning/touching Vibrating Surfaces 2.Whole Body Vehicles Vibrating Surfaces
Health Effects of Vibration Peripheral Neuropathies Sensory Deficits Vasoconstriction in Peripheral Limbs White Finger