👂Acoustics Unit 13 – Environmental Noise and Noise Control

What's Environmental Noise?

• Refers to unwanted or harmful outdoor sound created by human activities (transportation, industrial equipment, construction)
• Can negatively impact human health and well-being, as well as disrupt ecosystems and wildlife
• Characterized by its intensity (measured in decibels), frequency (low to high pitch), duration, and time of occurrence
• Differs from occupational noise exposure, which occurs in workplace settings
• Urban areas tend to have higher levels of environmental noise compared to rural areas
  • Due to higher population density and concentration of noise-generating activities (traffic, construction)
• Transient noise events (aircraft flyovers, train horns) can be particularly disruptive, even if they are relatively short in duration
• Low-frequency noise can travel farther and penetrate buildings more easily than high-frequency noise

Sources of Noise Pollution

• Transportation is a major contributor, including road traffic (cars, trucks, motorcycles), aircraft, and trains
• Industrial activities such as manufacturing plants, power generation facilities, and oil and gas operations
• Construction and demolition work, especially in urban areas
  • Use of heavy machinery (jackhammers, pile drivers)
  • Concentrated in specific areas and can be prolonged
• Recreational activities and events (concerts, sports stadiums, fireworks displays)
• Domestic sources (lawn mowers, leaf blowers, air conditioners, barking dogs)
• Natural sources can also contribute to environmental noise (thunder, ocean waves, animal vocalizations)
  • Generally not considered pollution unless they are unusually loud or persistent

Measuring Noise Levels

• Sound pressure level (SPL) is the most common measure, expressed in decibels (dB)
  • Logarithmic scale, with each 10 dB increase perceived as a doubling of loudness
• A-weighted decibels (dBA) are often used to account for human hearing sensitivity at different frequencies
• Equivalent continuous sound level (Leq) represents the average noise level over a given time period
• Day-night sound level (Ldn or DNL) adds a 10 dB penalty to nighttime noise levels to account for increased sensitivity
• Noise dosimeters can be worn by individuals to measure personal exposure over time
• Sound level meters are used for spot measurements and monitoring
  • Type 1 (precision) and Type 2 (general purpose) meters have different accuracy levels
• Noise mapping techniques use GIS and modeling software to visualize noise levels across a geographic area

Health Effects of Noise Exposure

• Hearing loss and tinnitus are the most direct effects, especially with prolonged exposure to high noise levels
• Sleep disturbance can lead to fatigue, decreased cognitive performance, and metabolic changes
• Cardiovascular effects include increased blood pressure, heart rate, and risk of hypertension and heart disease
• Mental health impacts such as stress, anxiety, and depression
• Cognitive impairment, particularly in children exposed to chronic noise
  • Difficulty concentrating, decreased memory and learning ability
• Annoyance and reduced quality of life, even at moderate noise levels
• Some evidence suggests links to birth outcomes (low birth weight, preterm birth) and diabetes risk
• Vulnerable populations (children, elderly, shift workers) may be at higher risk for adverse effects

Noise Control Strategies

• Source control: reducing noise at its origin through quieter equipment, maintenance, and operational changes
• Path control: blocking or absorbing sound along its path from source to receiver
  • Noise barriers (walls, berms) along highways or around industrial sites
  • Sound-absorbing materials (acoustic panels, vegetation) to reduce reflections
• Receiver control: protecting individuals through building design, insulation, and personal hearing protection
• Land use planning to separate noise-sensitive areas (residential, schools) from major noise sources
• Traffic management (speed limits, truck routes, low-noise pavement) to reduce transportation noise
• Operational restrictions (night-time construction bans, aircraft flight paths) to limit noise during sensitive hours
• Public education and outreach to promote awareness and change individual behaviors

Regulations and Standards

• Noise control laws and ordinances set by local, state/provincial, and national governments
  • May specify maximum allowable noise levels, restricted hours, or required mitigation measures
• World Health Organization (WHO) guidelines for community noise and environmental noise
  • Recommend limits to prevent adverse health effects (e.g., 45 dB Leq indoors at night)
• US Environmental Protection Agency (EPA) noise emission standards for products and equipment
• Federal Aviation Administration (FAA) and International Civil Aviation Organization (ICAO) aircraft noise certification standards
• Occupational safety and health regulations for workplace noise exposure (OSHA, NIOSH)
• International Organization for Standardization (ISO) standards for measuring and assessing environmental noise
• Green building rating systems (LEED, BREEAM) include credits for acoustic performance and noise control

Case Studies in Noise Management

• London Heathrow Airport: implemented noise abatement procedures, insulation grants for nearby homes, and night flight restrictions
• New York City: updated noise code with stricter limits on construction, air conditioning units, and music venues
• Paris: launched "Piezo" noise radar system to automatically ticket vehicles exceeding noise limits
• Dutch "Whisper Asphalt": special porous pavement designed to reduce tire-road noise by up to 6 dB
• Schiphol Airport in Amsterdam: uses ground noise control system to optimize aircraft movements and minimize community impact
• Hush City app: crowdsourced noise mapping and quiet area identification in urban environments
• Noise barriers along major highways in Japan, Hong Kong, and Australia
  • Some incorporate photovoltaic panels or vegetation for added environmental benefits

Future Challenges and Innovations

• Increasing urbanization and population growth will likely exacerbate noise pollution issues
• Climate change adaptation measures (air conditioning, ventilation) may introduce new noise sources
• Electric vehicles (EVs) are quieter but may pose safety risks for pedestrians who rely on auditory cues
  • Development of artificial vehicle sounds and warning systems
• Advancements in materials science for more effective and sustainable noise barriers and absorbers
• Integration of noise monitoring with smart city technologies and Internet of Things (IoT) devices
• Personalized noise exposure monitoring and real-time alerts through wearables and mobile apps
• Virtual and augmented reality (VR/AR) tools for visualizing and communicating noise impacts to stakeholders
• Nature-based solutions and urban green infrastructure to mitigate noise while providing other ecosystem services