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
Where is C-frequency weighting primarily used in?
for jet noise or relatively louder sounds
*Used to determine a time-integrated “peak” level with a time constant of no more than 0.05 ms
This weighting tries to approximate the frequency response of our hearing system
A-weighting
This weighting is used if the actual instantaneous pressure cannot be determined
C-weighting
This is intended to accurately estimate subjective evaluations of the same sound
Perceived Noise Level
*initially developed to rate jet aircraft noise
(See Typical Noise Levels of Some Point Sources)
(See Typical Noise Levels of Some Point Sources)
average noise level found in a study of noise in kindergartens
beyond 85 db (A)
*Most environmental spaces allow 85 db(A) for 8 hours
noise a conductor is being exposed to during a performance of swan lake
88 db (A)
exposure of noise level in truck drivers
89 db(A)
Staff in nightclubs
100 db(A)
noise on pig farms
115 db(A)
What are the objectives of noise measurements?
- Investigating complaints
- Assessing the number of persons exposed
- Compliance with regulations
- Land use planning and environmental impact assessments
- Evaluation of remedial measures
- Calibration and validation of predictions
- Research surveys
- Trend monitoring
Why is calibration and validation of predictions needed in noise measurements?
Characteristics of equipment can anticipate how much noise can be generated
What happens during land use planning and environmental impact assessments
- If observed area is industrial, residential, etc.
* EIA determines if it would be co-detrimental to the surrounding community
How are sound pressure levels provided?
instantantaneous sound pressures are integerated with some time constant
Most meters for measuring instruments include
fast-response
slow-response times
Fast-response time corresponds to a time constant of
- 125 seconds
* Intended to approximate the time constant of the human hearing system
This corresponds to a time constant of 1 second
Slow-response times
Why slow-response time?
An old concept intended to make it easier to obtain an approximate average value of fluctuating levels from simple meter readings
Parts of a sound level meter
- Microphone cover
- Buttons
- Scale
- Fast mode (used if the sound pressure level is relatively constant)
- Slow mode (used if it is fluctuating or unsteady)
- Peak mode is used for rare acoustic events
- Calibrator – specific to the instrument
Purpose of sound level meters?
To determine the effect of noise, measure at the site of exposure.
What is the hearing zone of a person?
a sphere with a foot radius with nose at the center
laboratory reference standard type of sound level meter
Type 0
Type of sound level meter primarily for field noise survey applications
Type 3
usual along with type 2
Type of sound level meter for laboratory use and for field use where the acoustical environment has to be closely specified and controlled
Type 1
Type of sound level meter for general field applications
Type 2
Where are noise measurement best taken in if not specified in local regulations?
close to the point of reception of the noise
If measurements are made close to the source, what must one do?
estimate the effect of sound propagation to the point of reception
T or F: The location should have a clear view of the source
True
[Sampling time]
Many environmental noises vary over time such as different times of the day or during different seasons
Ideally, the noise is measured throughout the exposure especially when variations of noise exposure occur (average)
Why are effects of noise pollution difficult to quanitfy?
variations in:
• Tolerance levels among different populace
• Types of noise
Effects of noise pollution may cause these
- Deafness
- Nervous breakdown
- Mental disorder
- Heart troubles
- High blood pressure
- Dizziness
- Insomnia
[Physiologic affects of noise]
Cardiovascular parameter
Alterations in the heart rate and blood
pressure
[Physiologic affects of noise] Metabolism parameter
Increased metabolic rate
[Physiologic affects of noise] Respiration parameter
Increased respiratory rate
[Physiologic affects of noise] Pupillary dilatation
Significant increase in pupillary size at sound levels beyond 55 dB
Pathologic auditory effects of noise
- Temporary or progressively permanent loss of hearing
* Transient/Temporary Threshold Shift (TTS)
It is the temporary hearing loss after exposure to high level of noise
(e.g. after concerts)
Transient/Temporary Threshold Shift
Pathologic NON-auditory effects of noise
- nervous pain and tinnitus
* sleeplessness: >30dB (A)
Pathologic NON-HEALTH effects of noise
- Communication interference: >35 dB(A) !!
- Annoyance and distraction: >55 dB(A) at daytime
- Annoyance
- Decreased working efficiency and work output
- Fatigue
Feeling of displeasure associated with any agent or condition, known or believed by an individual or group to adversely affect them.
Annoyance
Three major categories of occupational noise control
source, path and receiver
Three parameters to consider when we want to reduce exposure
frequency, intensity and duration
[Occupation noise control]
Usual practices would reduce what
intensity through encolsing and isolation machines
[Occupation noise control]
Practices in reducing frequency and durations includes
shift work or job rotations
General source of noise control
- Maintenance
- Substitution of Materials
- Substitution of Equipment
- Specification of a Quiet Equipment
- Substitution of Parts of Equipment
- Change of Work Methods
- Substitution of Processes
- Substitution of mechanical power generation and transmission equipment
- Replacement of worn moving parts
- Minimizing the number of noisy machines running at any one time
Control of Noise propagation
- Use of barriers, partial enclosures or full enclosure of the entire item of equipment
- Use of local enclosures for noisy components on a machine
- Use of reactive or dissipative mufflers
- Use of lined ducts or lined plenum chambers for air handling systems
- Reverberation control
Difference between reactive and dissipative mufflers
- Reactive mufflers: for low frequency or small exhausts
* Dissipative mufflers: for high frequency or large exhausts
It is the addition of sound absorbing material to reverberant spaces to reduce reflected noise fields
Reverberation control
Receiver control involves
- use of PPE (headsets, ear muffs or ear plugs)
- establishment of a sound reducing enclosure
- Administrative interventions - shift work
- Training and Education (most important)
Effectiveness of PPE depends on
noise reduction rating
T or F: earmuffs are not recommended when the user has ear infection
false, recommended
Environmental Noise, Residential Noise, or Domestic Noise
Community noise control
*all sources except industrial workplace
Main sources of community noise control
• Road, rail, and air traffic
• Industries
• Construction and Public Work and the neighborhood
• Indoor noise sources
(Ventilation systems, Home appliances, Office Machines, Neighbors)
Three major categories of community noise control
Legal, engineering, education and training
Legal measures involved in community noise control
- Control of noise emissions (emission standards)
- Control of Noise Transmission (regulations on sound obstructive
measures) - Noise-mapping and zoning around roads, airports and industries
(Initiation of monitoring and modelling programs) - Control of Noise Immissions
- Speed limits in residential areas and hospitals
- Enforcement regulations on low noise implementation plan
- Minimum requirements for acoustical properties of buildings (Construction codes for sound insulation of building parts)
Control of Noise immissions involve
- Introduction of additional noise apart from the existing background noise; “injection of noise”
- Limits for exposure levels such as national emmission standards
- Noise Monitoring and Modelling
- Regulations for complex noise situation
- Regulations for recreational hospital
These are regulations that show the limitations of community noise and to establish ambient noise quality standards areas within any city, region, or center of urban living shall be classified as follows
Ambient Quality And Emissions Standard For Noise
A section or contiguous area which required quietness, such as areas within 100 meters from school sites, nursery schools, hospitals and special homes for the aged
Class AA
*limitations become more lenient (A > D)
A section or contiguous area which is primarily used for residential purposes
Class A
A section or contiguous area which is zoned or used as a heavy industrial area
Class B
*includes small heavy industrial areas
A section which is primarily reserved, zoned or used as a heavy industrial area
Class D
*includes larger heavy industrial areas
A section primarily zoned or used as a light industrial area
Class C
(see Environmental Quality Standards for Noise in General Areas)
(see Environmental Quality Standards for Noise in General Areas)
Engineering measures for noise control
- Emission Reduction by Source Modification
- New Engine Technology
- Transmission Reduction
- Orientation of Buildings
- Traffic Management
- Passive Protection
- Implementation of Land Use Planning
[Engineering measures for noise control]
• Low-noise road surfaces
• Changes in engine properties
Emission Reduction by Source Modification
[Engineering measures for noise control]
• Road vehicles, aircraft, construction machines
New Engine Technology
[Engineering measures for noise control]
• Use of ear plugs, ear muffs
• Insulation of dwellings and façade design
Passive protection
[Engineering measures for noise control]
• Speed limits
• Guidance of traffic flows by electronic means
Traffic Management
[Engineering measures for noise control]
What are involved in orientation of buildings?
- Design and structuring of buildings
- Using buildings for screening purposes
- Orienting buildings to reduce reflecting noise
[Engineering measures for noise control]
How is transmission reduced?
• Enclosures around machinery; noise screens
[Engineering measures for noise control]
What are involved in Implementation of land use planning
- Minimum distance between industrial and residential areas, and busy roads
- Location of tranquility areas
Education and Training involves
- Raising Public Awareness
(Informing the public on the health impacts of noise, enforcement action taken, noise levels, complaints) - Monitoring and Modelling Soundscapes
(Publication of results) - Sufficient Number of Noise Experts
- Initiation of Research and Development
- Initiation of Behavioral Changes
• Speed reduction when driving
• Use of horns
• Use of loud speakers for advertisements
