All About Noise (Basic Facts You Need Know)
All About Noise (Basic Facts You Need Know)
Noise is defined as wrong sound in wrong place and at wrong times. Noise is created when an object vibrates.
Introduction
- Noise is defined as wrong sound in wrong place and at wrong times.
- Noise is created when an object vibrates
- Air is compressed and expanded forming waves
- These varying pressure waves travel outward from source in all directions
- Noise waves have frequency and amplitude
- Excessive noise can be damaging
Sources of Noise
- Automobiles
- Factories
- Industries
- Radio and television
- Air crafts
Properties of Noise
Noise has following two important properties.
a) Loudness
b) Frequency
a) Loudness
- It depends upon the amplitude of vibrations which initiate the noise. It is measured in decibels (dB). When we say that sound is 60 dB, it means that it is 60 dB more intense than the smallest distinguishable noise.
- Whispering—-20-30dB
- Normal conversation—–60-65dB
- Heavy traffic——-60-80dB
- Threshold of pain——-140dB
b) Frequency
- The frequency is denoted by Hertz (HZ).
- One (HZ) is equal to one wave per second.
- The human ear can hear frequencies from 20-20,000Hz. But this range is reduced with age and other subjective factors.
- Infra audible sound—–below 20 Hz
- Ultrasonic sound———–above 20 Hz.
Acceptable Noise Levels
1. Residential
- Living room – 40 dB
- Bed room – 25 dB
2. Industrial
- Laboratory – 40 to 50 dB
- Workshop – 40 to 60 dB
3. Commercial
- Office – 35 to 45 dB
- Restaurant – 40 to 60 dB
- Conference – 40 to 45 dB
4. Educational
- Class room – 30 to 40 dB
- Library – 35 to 40 dB
5. Hospital
- Wards – 20 to 35 dB
Effects of Noise
- Auditory effects
- Non-auditory effects
1. Auditory Effects
a) Auditory fatigue
b) Deafness
a) Auditory Fatigue
Auditory fat appears in the 90 dB region and is greatest at 4000 Hz. It may be associated with tinnitus and buzzing.
b) Deafness
Most lethal pathological effect of noise is deafness and hearing loss. It may be temporary as well as it may be permanent. Temporary deafness occurs with the frequency range 4000-6000 Hz region, while permanent deafness occurs after repeated exposure to the high frequency noise around 100 dB. Exposure to the noise above 160 dB may cause rupture of tympanic membrane.
2. Non-auditory Effects
- Interference with speech, frequency lays between300-500Hz range. Noise interferes with communication and may cause disruption of speech or lecture.
- Annoyance: Annoyance is a psychological response to the noise. Neurotic people are more prone to noise than the normal people.
- Efficiency: Efficiency of the work decreases due to loss of attention. Reduction in noise causes increase in output of work.
- Psychological Changes.
- Rise in blood pressure.
- Rise in intracranial pressure.
- Rise in heart rate.
- Increased sweating.
- Visual disturbances
- Disturbed sleep
- Giddiness, nausea
- Fatigue
Noise Control
- Careful planning of the cities.
- Control at sources.
- Control of Transmission.
- Protection of exposed persons.
- Legislations.
- Education.
- There should be division of city into zones and separate areas for industries, wide road and green belts.
- Control at source:
- Should be controlled at source of its pollution. This can be achieved by segregating noisy machines, application of noisy mufflers, etc.
- Control of transmission
- Building enclosures and covering room walls with absorbing material achieve this. Building should be sound proof where necessary.
- Protection of exposed persons.
- Exposed persons must use earplugs. They must be regularly checked and rotated from noisy places to quiet places.
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