Sound

UPSC GS3 — Infrasound in Science and Security:

• Animal early warning: Elephants communicate using infrasound calls (14-35 Hz) audible to other elephants up to 10 km away. Elephants, dogs, and some other animals can detect infrasound from approaching earthquakes before seismic instruments register them — basis of animal-based early warning research.
• CTBTO (Comprehensive Nuclear-Test-Ban Treaty Organization): The CTBTO's International Monitoring System (IMS) includes 60 infrasound monitoring stations globally. Nuclear explosions, large volcanic eruptions, and meteor airbursts produce characteristic infrasound signatures. CTBTO detected the 2013 Chelyabinsk meteor (Russia) via infrasound. India's signing/ratification status of CTBT is a recurring UPSC topic: India has not ratified the CTBT (Comprehensive Nuclear-Test-Ban Treaty) — one of 8 Annex 2 states whose ratification is required for it to enter into force (along with USA, China, Pakistan, etc.).
• Tsunami early warning: Tsunamis generate infrasound and low-frequency seismic waves — detectable before the wave arrives at shore; basis of INCOIS (Indian National Centre for Ocean Information Services) tsunami early warning system.

UPSC GS3 — Ultrasound Technology: Medical Sonography: Ultrasound (2-18 MHz range) penetrates soft tissues and reflects off boundaries between different tissue densities, creating real-time images. It is safe (no ionizing radiation — unlike X-rays or CT scans), portable, and relatively inexpensive. Applications:

• Pregnancy monitoring (fetal development, fetal sex — but sex determination banned under PC&PNDT Act 1994)
• Organ examination (liver, kidney, gallbladder stones)
• Echocardiography (heart ultrasound)
• Doppler ultrasound (blood flow measurement)

SONAR (Sound Navigation And Ranging): Active SONAR: Emits ultrasound pulses; measures time for echo to return → calculates distance. Applications:

• Submarine detection: Navy uses hull-mounted and towed array SONAR; sonobuoys dropped from aircraft; India's P-8I Poseidon maritime patrol aircraft use SONAR to detect Pakistani and Chinese submarines
• Ocean floor mapping: Multibeam SONAR maps bathymetry — India's NIOT and NCPOR (National Centre for Polar and Ocean Research) use this for deep-sea mineral surveys
• Fish finder: Commercial fishing vessels use SONAR to locate fish shoals — important for India's blue economy (marine fisheries GDP ~₹1.8 lakh crore)

Passive SONAR: Listens for sounds emitted by submarines/ships without emitting; harder to detect but lower range. India's Andaman and Nicobar Islands host passive underwater acoustic monitoring assets.

Industrial Non-Destructive Testing (NDT): Ultrasound detects internal cracks in metal structures (railway tracks, aircraft components, pressure vessels, pipelines) without cutting them — critical for infrastructure safety. Indian Railways conducts ultrasonic flaw detection on rails using USFD (Ultrasonic Flaw Detection) trolleys.

UPSC GS3 — Noise Pollution Regulation: Noise Pollution (Regulation and Control) Rules, 2000 (under EPA 1986):

• CPCB standards (see table above)
• States can declare "Silence Zones" around hospitals, educational institutions, courts, religious places
• Firecrackers: Only between 6 PM – 10 PM on permitted occasions
• State Pollution Control Boards (SPCBs) enforce noise standards

Supreme Court on Firecrackers (2018 — Arjun Gopal v. Union of India): SC directed that only "green crackers" with reduced sound emission and chemical content be permitted near Diwali in NCR. CSIR-NEERI (National Environmental Engineering Research Institute) developed three certified green cracker formulations: SWAS (Safe Water Releaser -- emits steam/water vapour), STAR (Safe Thermite Cracker -- reduced KNO3 and sulphur), and SAFAL (Safe Minimal Aluminium Firework). Verified reductions: 30-40% lower PM2.5/PM10 vs traditional crackers; noise reduced by up to 125 dB vs conventional fireworks. [Additional] October 2025 update: SC (Chief Justice BR Gavai) partially relaxed the blanket ban, permitting certified green cracker sale offline at designated locations in Delhi-NCR for Diwali 2025 (Oct 18-20), use allowed 8 PM-10 PM on Diwali days. Implementation challenges persist: counterfeiting of NEERI certification marks, limited manufacturing capacity, cost (~2x conventional), and smuggling of conventional crackers into the NCR.

Health Impacts of Noise:

• Hearing impairment: Exposure to >85 dB for 8+ hours/day causes permanent hearing loss (NIHL — Noise Induced Hearing Loss); WHO estimates 1.1 billion young people at risk globally from recreational noise
• Cardiovascular effects: Chronic noise → stress hormone release (cortisol, adrenaline) → hypertension, increased heart disease risk; WHO evidence review (2011) linked night noise >40 dB to cardiovascular disease
• Sleep disturbance: Cognitive impairment, reduced productivity
• Academic performance: Schools near airports or highways show lower student test scores (international studies; DPCC data for Delhi schools near roads)

Green Belts as Noise Barriers: A dense row of trees (mixed species, multiple layers) can reduce noise by approximately 6–10 dB per 30-metre width. Delhi's green belt along Ring Road and NH48 serve dual purpose — noise attenuation and air pollution buffering. CPCB recommends green buffer zones around industrial areas.

[Additional] Underwater/Ocean Noise Pollution -- GS3 (Environment / Blue Economy / International Bodies):

Sources of anthropogenic underwater noise:

• Commercial shipping: The world's ~90,000 commercial vessels generate continuous broadband low-frequency noise from propellers and engines; shipping traffic has doubled in recent decades; dominant source of chronic ocean noise globally
• Seismic airguns: Used for offshore oil and gas exploration -- emit intense sound pulses (up to 260 dB, fired every 10-15 seconds for hours/days); effective range for seafloor mapping: hundreds of kilometres; but kills zooplankton within ~1.2 km radius per shot and damages internal organs of giant squid and fish
• Military SONAR (active high-intensity): Mid-frequency active sonar used for submarine detection; linked to cetacean mass strandings -- acoustic trauma disrupts dive physiology of beaked whales
• Offshore construction: Pile-driving for wind turbines, oil platforms -- intense impulsive noise

Impact on marine life:

• Communication masking: Blue whales, humpback whales, and dolphins communicate over hundreds/thousands of km using sound; anthropogenic noise overlaps their frequency ranges, drowning out calls and disrupting social bonds, mating, feeding coordination, and navigation
• Behavioral disruption: Forced changes in migration routes, habitat abandonment, reduced foraging efficiency
• Physiological harm: Chronic stress hormones, hearing threshold shift (temporary/permanent), in extreme cases acute barotrauma
• Frequency shift: Some dolphin species have shifted their vocalization frequencies upward over decades to avoid masking by shipping noise -- an evolutionary-scale adaptation under anthropogenic pressure

Global governance:

• IMO Guidelines for the Reduction of Underwater Noise from Commercial Shipping (2014): Adopted by the International Maritime Organization; emphasis on quieter ship design (propeller design, hull form, engine mounting isolation) -- voluntary guidelines only, not binding regulation
• [Additional] UNOC 2025 -- High Ambition Coalition for a Quiet Ocean: At the Third UN Ocean Conference (UNOC 3, Nice, France, June 2025), 37 countries led by Panama and Canada launched the first high-level political coalition to address ocean noise: commitments include pushing for binding IMO noise standards for ships, incorporating acoustic criteria into Marine Protected Areas (MPAs), and expanding the IMO GloNoise Partnership monitoring tools
• International Whaling Commission (IWC) and IUCN formally recognise anthropogenic sound as a priority threat to cetaceans

India-specific gap:

• India has comprehensive surface noise regulation (Noise Pollution Rules 2000, CPCB standards, EPA 1986) but no dedicated underwater noise regulation as of 2025
• India's Blue Economy Framework 2023 covers fisheries, shipping, and tourism but does not mention underwater noise standards
• India has not confirmed joining the UNOC 2025 Quiet Ocean Coalition

UPSC GS3 angle: This is a textbook "policy lacuna" question -- contrast India's robust terrestrial noise regulation with its absence of marine noise governance. Also connects to Blue Economy (Rs 1.8 lakh crore marine fisheries + shipping), biodiversity (cetaceans protected under Schedule I WPA 1972), and international treaty law (IMO, CBD, CITES).