Control of Environmental Noise and Sound Nature

Study Notes

Noise is defined as unwanted or undesirable sound, lacking agreeable quality.
Noise problems are categorized into community noise (annoyance from indoor environments, primarily vehicular traffic) and intense noise (workplaces, factories; potentially causing permanent physical damage).
Prolonged exposure to excessive noise can cause adverse physiological effects like hypertension, annoyance, sleep disruption, and hearing loss (deafness).
Sound level (L) is measured as L = 10 log10 (Q/Q0) in Bels, where Q = sound pressure/power/intensity and Q0 = reference standard.
For practical use, Bels are divided into decibels (dB), making L = 10 log10(Q/Q0) (dB).
A safe noise level in a city is considered 45 dB by the WHO (World Health Organization).
65 dB is a tolerable noise level according to international standards.

Sound is a sensation caused by vibrations in a medium (air, liquid) that transmit as longitudinal waves (compressions/rarefactions of molecules).
The source of sound is often vibrating solids.
The human ear can perceive frequencies from approximately 29 to 16000 Hz (hertz).
The lowest intensity (threshold of audibility) is 10⁻¹² W/m².
The highest intensity (threshold of pain) is 1 W/m².
Exceeding 1 W/m² intensity can cause pain and damage to the human ear.

Noise effects vary based on the noise level, exposure time, and general health conditions.
At 65 dB, noise may create annoyance, leading to mental/physical fatigue.
Extended exposure to 90 dB noise can cause permanent hearing loss.
Temporary impairment of aural acuity can result from short-term 100 dB exposure; prolonged exposure can cause irreparable damage to the auditory organ.
120 dB or higher noise levels can cause pain and significant damage to human beings; a sudden 150 dB noise may lead to instant hearing loss.
Noise exposure can activate the sympathetic nervous system, similar to heat, cold, or pain. This can affect blood circulation, insulin levels, and potentially cause stomach ulcers, allergies, circulatory diseases, abortion, and congenital defects. Noise can also reduce the flow of gastric juice, modify acidity, and affect various other bodily functions.

Noise is a primary cause of sleep interruption, leading to short temper, fatigue, and general discomfort, even if the person does not fully wake up.

Efficiency decreases with increased noise levels.
96-87 dB noise reduction results in a 12% performance improvement.
Noise control, including soundproofing, and barriers improve work quality and reduce workplace accidents.

Noise has adverse physiological effects on animals.
Animals like deer, lions, rhinos, and migratory birds are especially susceptible.
Noise exposure may result in inactivity, reproductive issues (less breeding), and illness (illness, weakness).
Noise severely affects animals in forested areas.

High-intensity noise can damage buildings (cracks, loosened plaster).
Noise/vibration from machinery can result in foundation issues, cracks in walls, and structural damage to household items.

Noise control measures aim to reduce, not eliminate, noise.
Noise control at the source involves using silencers, better material usage, and reducing peak vibrations and flow velocities.
Noise control along the path includes barriers (solid fences/high earth walls) and increasing the distance between the source and receiver.
Planting trees is a sound management technique.
Additional actions at the receiving end include double-glazing windows, improved soundproofing, additional sound insulation, isolating operators from sources, reducing noise exposure time, and protective devices (earplugs, ear defenders, disposable earplugs).

Noise legislation, regulating equipment, using silence zones, limiting loudspeaker use, and public awareness campaigns can significantly reduce noise pollution.