Environmental Noise Control Quiz

Study Notes

Noise is defined as unwanted or undesirable sound.
Community noise involves noise levels inside dwellings, mainly from traffic.
Intense noise in workplaces (factories, etc.) can cause permanent physical damage.
Noise exposure leads to harmful physiological effects like hypertension, annoyance, sleep disturbance, and hearing loss.

Sound level (L) is measured in Bels (B) or decibels (dB)
L = log10(Q/Q0) (B), where Q is the measured sound pressure, sound power, or intensity, Q0 is the reference standard quantity
L = 10 log10(Q/Q0) (dB) is the more common expression, convenient for practical use
A safe noise level in a city is considered as 45 dB by WHO.
A noise level of 65 dB is considered tolerable according to international standards

Sound is the sensation caused by a vibrating medium on the ear.
Vibrations in solids, gases (air), and liquids generate sound waves.
Sound waves are longitudinal, consisting of successive compressions and rarefactions of molecules.

People can hear frequencies between roughly 20Hz to 20,000 Hz (subjective factors can apply)
The lowest intensity perceived as sound is 10^-12 W/m² (threshold of audibility)
An intensity of 1 W/m² is the threshold of pain, potentially damaging to the ear.

Noise effects vary with level, exposure time, and health conditions.
65 dB: annoyance, psychological effects
90 dB: potential for permanent hearing loss (repeated exposure)
100 dB: temporary impairment of hearing with short exposure; severe damage with repeated exposure
120 dB: pain, potential harm to many organs
150 dB: instant hearing loss
Noise exposure can activate the sympathetic nervous system, impacting blood circulation, the brain, and other organs.
It can affect hormone levels, reducing detoxifying functions in the liver, potentially causing stomach ulcers and allergies
Long-term exposure can lead to circulatory diseases, abortion, and congenital defects.

Noise can interrupt sleep, leading to short-temperedness, fatigue, and reduced efficiency the next day.

Noise decreases working efficiency.
Noise reduction methods like better soundproofing or barrier design can improve worker performance and safety (reduced accidents).

High noise levels can damage buildings (cracks, weakened foundations, loosened plaster).
Noise can also harm household items.

Noise cannot be entirely eliminated but can be reduced through different methods
Controlling the source of the noise via machinery modification
Preventing sound transmission through barriers or increasing distance between the source and receiver.
Using noise-absorbing materials.
Personal protective gear (earplugs, etc) and reduced usage times or locations of potentially harmful noise activities.