Concept about Noise – This book covers the entire syllabus of “Community Health Nursing” prescribed by the Universities of Bangladesh- for Basic and diploma nursing students. We tried to accommodate latest information and topics.
This book is examination friendly setup according to the teachers’ lectures and examination’s questions. At the end of the book previous university questions are given. We hope in touch with the book students’ knowledge will be upgraded and flourished. The unique way of presentation may make your reading of the book a pleasurable experience.
Concept about Noise
Definition
Noise is defined as sound without agreeable musical quality, or as an unwanted or undesired sound.
Sources of noise
The sources of noise are many and varied. These are –
- Domestic: Transistor, Radios, TV etc.
- Automobiles and railways.
- Factories and industries.
- Aircraft.
- Public places like market, fairs, playground etc.
- Construction equipment.
- Animals.
Properties of noise
It has two important properties-
1. Loudness or intensity. It depends upon the amplitude of the vibrations which initiated the noise.
- a. The loudness of noise is measured in decibels (dB). When it is said that sound is 70 dB, it means that it is 70 dB more intense than the smallest distinguishable noise or the “reference” sound pressure, which is understood to be 0.0002 microbar or dynes/cm2
- b. Normal conversation produces a noise a noise of 60-65 dB; whispering, 20-30 dB: heavy street traffic, 60-80 dB; and boiler factories, about 120 dB.
- e. A daily exposure up to 85 dB is about the limit people can tolerate without damage to their hearing.
2. Frequency. It is denoted by Hertz (Hz). 1 Hz is equal to one wave per second.
- a. The human ear can hear frequencies from about 20 to 20,000 Hz
- b. The range of vibrations below 20 Hz are infra-audible; and those above 20,000 Hz ultra- sonic.
Effects of noise
1. Auditory effects:
a. Auditory fatigue, may be associated with whistling and buzzing in the ears. It appears in the 90 dB region and greatest at 4000 Hz.
b. Deafness or hearing loss, may be temporary or permanent.
- Most temporary hearing loss occurs in frequency range between 4000 to 6000 Hz.
- Repeated or continuous exposure to noise around 100 dli may result in a permanent hearing loss. When this occurs as a result of occupation in industries, it is called “occupational hearing loss”.
- Exposure to noise above 160 dB may rupture the tympanic membrane and cause permanent loss of hearing.
2. Non-auditory effects:
a. Interference with speech: The frequencies causing most disturbance to speech communication lie in the range of 300-500 Hz. Such frequencies are commonly present in noise produced by road (motor vehicles) and air (air crafts) traffic. [For good speech intelligibility, the speech, sound level must exceed the SIL (Speech Interference Level) by approximately 12 dB.]
b. Annoyance: primarily a psychological response.
c. Diminished efficiency: inability to concentrate. Reduction in noise has been found to increase work output.
3. Physiological effects:
- Rise in blood pressure
- An increase in heart rate and breathing
- Rise in intracranial pressure
- An increase in sweating
4. Other effects:
- General symptoms such as giddiness, nausea, fatigue.
- Interferes with sleep
- Cause narrowing of pupil
- Cause visual disturbance
- Affects night vision.
Methods of noise control
A. Noise control at source: This is the most effective and can be achieved by –
- Designed acoustic control in new equipment. Mechanical redesigning of machines now in use.
- Isolation of noisy machines in a comer of the factory. Application of mufflers and other sound reducing materials.
- Reduction in the amount of noise transmitted through the air or building structure.
B. Control of transmission of noise: This may be achieved by –
- Building enclosures, and
- Covering the room walls with sound absorbing materials.
C. Protection of exposed persons:
- Regular rotation of workers from noisy areas to comparatively quiet posts in factories.
- Use of ear plugs, ear muffs.
- Periodical audiogram check-up.
D. Legislation
- Declaration of noise free area, e.g. hospitals, schools, colleges.
- Compensation of workers if they have suffered a loss of ability to understand speech due to excess noise.
E. Public education
- Without people’s participation noise abatement programme cannot be succeeded.
- Public education through all available media is needed.
- It is to be high-lighted that noise abatement is important as a community hazard.
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