Definition of Noise

Noise:

• Noise is typically defined as any unwanted or disturbing sound that interferes with normal activities such as sleeping, conversation, or other routine activities.
• From a scientific perspective, noise is a type of sound characterized by its irregular waveform and lack of harmonic content compared to musical sounds.
• Noise can be subjective; what is considered noise to one person might not be to another. For example, loud music might be pleasant to some but disturbing to others.

Effects of Noise Pollution

Health Effects:

• Hearing Loss: Prolonged exposure to high noise levels can cause permanent hearing damage.
• Stress and Anxiety: Continuous exposure to noise can increase stress levels, leading to anxiety and related disorders.
• Cardiovascular Issues: Elevated noise levels can lead to high blood pressure, increased heart rate, and a higher risk of heart diseases.
• Sleep Disturbances: Noise can disrupt sleep patterns, leading to fatigue, decreased productivity, and overall poor health.
• Cognitive Effects: Particularly in children, noise pollution can affect learning and concentration, leading to decreased cognitive performance.

Environmental Effects:

• Wildlife Disruption: Many animals rely on sound for communication, navigation, and detecting predators. Noise pollution can interfere with these essential activities, affecting animal behavior and survival.
• Quality of Life: Excessive noise can reduce the quality of life by interfering with daily activities, reducing property values, and causing psychological stress.
• Communication Interference: Noise pollution can make verbal communication difficult, leading to misunderstandings and reduced social interaction.

Noise classification

Transport Noise:

• Road Traffic Noise: Includes sounds from cars, trucks, motorcycles, and buses. This is often the most pervasive type of noise in urban environments.
• Air Traffic Noise: Noise from airplanes during takeoff, landing, and while flying over populated areas.
• Rail Traffic Noise: Noise generated by trains, including engine noise, wheel-rail interaction, and signal horns.

Occupational Noise:

• Industrial Noise: Noise from machinery, tools, and industrial processes commonly found in factories and manufacturing plants.
• Construction Noise: Sounds from construction sites, including heavy machinery, demolition, and building activities.
• Office Noise: In some cases, office environments can have significant noise from equipment like printers, telephones, and HVAC systems.

Neighborhood Noise:

• Residential Noise: Includes loud music, television sounds, and household appliances like vacuum cleaners and washing machines.
• Social Noise: Noise from social gatherings, parties, and public events.
• Animal Noise: Sounds from pets such as barking dogs and other domestic animals.
• Miscellaneous Noise: Other types of noise that can be found in residential areas, such as lawn mowers, leaf blowers, and car alarms.

Noise Frequency, Pressure and Intensity

Noise Frequency:

• Definition: Frequency is the number of sound wave cycles that pass a fixed point per second. It is measured in Hertz (Hz).
• Perception: Frequency determines the pitch of the sound. Higher frequencies correspond to higher-pitched sounds, while lower frequencies correspond to lower-pitched sounds.
• Range: Humans can generally hear frequencies from 20 Hz to 20,000 Hz (20 kHz). Sounds below 20 Hz are called infrasound, and sounds above 20 kHz are called ultrasound.
• Examples:
  • A low-frequency noise could be a deep rumble from thunder or heavy machinery.
  • A high-frequency noise could be a whistle or the sound of a mosquito.

Noise Pressure

Noise Pressure (Sound Pressure):

• Definition: Sound pressure is the local pressure deviation from the ambient (average or equilibrium) atmospheric pressure caused by a sound wave. It is measured in Pascals (Pa).

• Perception: The amplitude of the sound pressure wave determines the loudness of the sound. Greater sound pressure corresponds to louder sounds.

• Measurement: Sound pressure level (SPL) is often measured in decibels (dB), which is a logarithmic scale. SPL is calculated using the formula:

• 

• Examples:

  • Normal conversation has a sound pressure level of around 60 db.
  • A rock concert might have levels around 110-120 db.

Noise Intensity

Noise Intensity (Sound Intensity):

• Definition: Sound intensity is the sound power per unit area, which quantifies the energy of the sound wave. It is measured in watts per square meter (W/m²).
• Perception: Intensity is also related to loudness, but it is a measure of energy transfer rather than pressure.
• Measurement: Like sound pressure level, sound intensity level can also be expressed in decibels (dB), using the formula:

• Examples:
  • Whispering has a low intensity, around 10−1210^{-12}10−12 W/m².
  • A jet engine at close range can have an intensity of 10−210^{-2}10−2 W/m² or higher.

Summary of Differences

• Frequency is about the rate of sound wave cycles per second and determines the pitch of the sound.
• Pressure is about the force of the sound wave on a surface and determines the loudness of the sound.
• Intensity is about the energy transfer of the sound wave per unit area and also relates to the loudness of the sound.

Noise Threshold limit value, equivalent noise level

Noise Threshold Limit Value (TLV)

Noise Threshold Limit Value (TLV):

• Definition: The Noise Threshold Limit Value (TLV) represents the maximum permissible noise exposure level for a specified period, usually to protect workers' hearing and health. It is set by regulatory agencies such as the Occupational Safety and Health Administration (OSHA) or the Environmental Protection Agency (EPA).
• Measurement: TLVs are often measured in decibels (dB) over a standardized period, such as an 8-hour workday.
• Examples:
  • OSHA's permissible exposure limit (PEL) for workplace noise is 90 dB for an 8-hour day.
  • For every 5 dB increase in noise level, the allowable exposure time is halved. For instance, at 95 dB, the maximum exposure time is 4 hours.
• Purpose: The TLV is designed to prevent hearing loss and other health issues associated with prolonged exposure to high noise levels.

Equivalent Noise Level (Leq) (only study if you have time)

Equivalent Noise Level (Leq):

• Definition: The Equivalent Noise Level (Leq) is a single number that represents the constant noise level that would have the same acoustic energy as the varying noise levels measured over a specific period.

• Calculation: Leq is calculated using the formula:
  

• Examples:

  • If the noise levels fluctuate between 50 dB and 70 dB over an hour, the Leq might be around 65 dB, representing the average energy level of the noise.

• Usage: Leq is widely used in environmental noise assessments, urban planning, and noise control engineering because it provides a comprehensive measure of exposure over time.

Noise pollution control

Noise Pollution Control:

• Source Control:
  • Design and Engineering: Using quieter machinery and equipment, implementing better engine designs, and adding noise-reducing features.
  • Maintenance: Regular maintenance of machinery and vehicles to ensure they operate quietly.
• Path Control:
  • Barriers: Installing sound barriers such as walls, fences, or earthen berms to block or absorb noise.
  • Vegetation: Planting trees and shrubs can help to attenuate noise by providing a physical barrier.
  • Distance: Increasing the distance between the noise source and the receiver.
• Receiver Control:
  • Soundproofing: Installing double-glazed windows, insulation, and soundproofing materials in buildings to reduce noise penetration.
  • Personal Protective Equipment (PPE): Providing earplugs or earmuffs to workers in noisy environments.
• Administrative and Regulatory Measures:
  • Zoning Laws: Implementing zoning laws to separate industrial areas from residential areas.
  • Noise Ordinances: Establishing and enforcing noise limits for different areas and times of day.
  • Public Awareness Campaigns: Educating the public about the sources and effects of noise pollution and encouraging behaviors that reduce noise.
• Technological Innovations:
  • Active Noise Control: Using technology such as active noise-canceling headphones or devices that emit sound waves to cancel out noise.
  • Smart City Solutions: Incorporating noise monitoring and control into urban planning through smart city technologies.

Summary

• Noise Threshold Limit Value (TLV) is the maximum allowable noise level for a specific period to prevent health issues, particularly in occupational settings.
• Equivalent Noise Level (Leq) provides an average noise level over time, representing the varying noise levels' energy equivalent.
• Noise Pollution Control encompasses various strategies to reduce noise at the source, along its path, or at the receiver, including technological, administrative, and public awareness measures.