Noise Pollution Flashcards
These are longitudinal waes undergoing successions of compressions and rarefactions (expansions) occurring due to vibrations in a medium (solid, liquid, gas) where the vibrating source is located
Acoustic waves
Acoustic waves falling within the range capable of exciting the sense of hearing
Sound waves
Unwanted sound or sound that is loud, unpleasant, or unexpcted; disagreeable or undesirable sound
Noise
What are the types of noise?
Steady Noise
Non-steady noise
Impulsive or impact noise
Type of noise with negligibly small fluctuations of sound pressure level within the period of observation
Steady noise
Noise which consists of one or more bursts of sound energy, each of a duration less than about one second
Impulsive/Impact noise
occur in rare acoustic events
type of noise where pressure levels shift significantly during the period of observation
Non-steady noise
Sources of noise and examples
Domestic (Movement of utensils, Cutting and peeling of fruits)
Natural (Shores, Birds, Wind movement)
Commercial (Vendors, automobiles, machinery)
Industrial (Generator sets, Motor, Boilers)
How are sound waves characterized?
Amplitude of pressure changes (Pa)
Wavelength
Frequency (Hz)
Period
It is the measurement of degree of change of atmospheric pressure
Amplitude of pressure changes (Pa)
T or F: Sound waves with lower amplitude will produce greater changes in atmospheric pressure
False, greater amplitude
**Silence will produce the lowest amplitude
Distance travelled by the pressure wave during one cycle
Wavelength
T or F: Human beings generally have the ability to hear sounds in the frequency range of 30 to 30000 Hz.
False, 20 to 20,000 Hz
*Human hearing is more sensitive to frequencies in the range of 500 to 6000 Hz and less sensitive in both the lower and higher frequencies.
It is the number of pressure variation cycles in the medium per unit time (i.e.: The number of cycles per second)
Frequency
It is the time taken for one cycle of a wave to pass a fixed point
Period
Basic measure of vibrations in the air which make up sound
Sound pressure
Sound pressure is expressed in terms of what?
datum pressure
*corresponding to the sound pressure level, Lp or SPL
What is the lowest sound pressure which the young normal ear can detect?
SPL
What is the minimum acoustic pressure audible to the young human ear in good health?
approximately 20 x 10-6 Pa
Why is sound pressure measured in a logarithmic scale in decibels?
range of the audible sound pressure is very wide
T or F: Most environmental sounds are made up of complex mix of many frequencies with this variety challenging our hearing systems
True
What have been used to determine the relative strengths of frequency components making up a particular environmental noise?
Various types of filters or frequency weighing
It is the most common sound weighing wherein weights lower frequencies as less important than mid- and high range frequencies
A-weighting
This sound weighting is also known as linear frequency weighting
C-Frequency weighting