AP® Environmental Science review sheet from Aim for Five (aimforfive.com/enviro/units/7/7-8)
Unit 7 · Topic 7.8
7.8 Noise Pollution
Noise pollution is sound loud or constant enough to harm people or wildlife. Traffic, construction, airports, industry and ships are the main sources; noise can damage hearing, cause stress and sleep loss, and interfere with how animals communicate, hunt, mate and migrate.
Key terms
- noise pollution
- decibel (dB)
- physiological stress
- wildlife communication
Measuring sound: the decibel scale
Sound intensity is measured in decibels (dB). Like pH, the decibel scale is logarithmic. An increase of 10 dB means the sound carries 10 times as much energy (intensity), and people hear it as roughly twice as loud. An increase of 20 dB is 100 times the intensity.
Long or repeated exposure to sound above about 85 dB can permanently damage hearing by destroying the tiny hair cells in the inner ear, which don't grow back. Very loud sounds, around 120 dB and up, can cause pain and immediate damage.
| Sound | Approximate level |
|---|---|
| Whisper | 30 dB |
| Normal conversation | 60 dB |
| Busy city traffic | 80–85 dB |
| Lawn mower or motorcycle | 90–95 dB |
| Rock concert, siren up close | 110–120 dB |
| Jet engine at close range | 140 dB |
Where noise pollution comes from
- Transportation: road traffic, trains and aircraft are the most widespread sources, and they affect the most people.
- Construction and industry: jackhammers, pile drivers, heavy machinery and factory equipment.
- Urban life: sirens, loudspeakers, nightlife and air-conditioning units in crowded cities (topic 5.10).
- Energy and resource extraction: drilling rigs, mining blasts and compressor stations.
- The ocean: shipping traffic, seismic airgun surveys for oil and gas, sonar and offshore construction.
Effects on people
- Hearing loss and ringing in the ears (tinnitus) from loud or long exposure.
- Physiological stress: noise raises stress hormones, heart rate and blood pressure, and long-term exposure is linked to heart disease.
- Sleep disruption, which affects health, mood and learning.
- Reduced concentration; studies have linked aircraft noise near schools to lower reading performance.
Effects on wildlife
Many animals depend on sound to find mates, warn of predators, locate prey and keep groups together. Noise masks those signals. Some city birds sing louder or at a higher pitch to be heard over traffic, and some species avoid noisy roadsides altogether, shrinking their usable habitat.
Sound travels far and fast in water, so the ocean is especially affected. Ship engines, oil and gas exploration using seismic airguns, offshore construction and military sonar make the ocean much noisier than it used to be. Whales and dolphins use sound to communicate and navigate, and noise can mask their calls, change their migration routes and stress them. Intense military sonar has been linked to strandings of some whale species.
Reducing noise
Solutions include noise barriers (walls) along highways, quieter engines, tires and road surfaces, zoning that keeps homes away from airports and industry, flight-path and curfew rules at airports, ear protection for workers, and slower speeds or quieter propeller designs for ships in sensitive whale areas.
Worked examples
Try each one yourself first, then open the solution.
- Example 1
Comparing sound intensities
A construction site produces 90 dB at the property line. A quiet suburban street is 70 dB. How many times more intense is the construction noise?
Show the solutionHide the solution
- Step 1: Find the difference: 90 − 70 = 20 dB.
- Step 2: Every 10 dB is a factor of 10 in intensity. 20 dB is two steps of 10: 10 × 10 = 100.
- Step 3: Formula version: intensity ratio = 10 raised to the power (difference ÷ 10). Here that is 10 to the power 2, or 10² = 100.
Answer: 100 times more intense (and it sounds roughly four times as loud).
- Example 2Calculator allowed
Trap: reading dB as linear
A student says a 100 dB concert is 'only about 18% louder' than 85 dB city traffic, because 100 is 18% more than 85. What is wrong?
Show the solutionHide the solution
- Step 1: Decibels are logarithmic, so you compare differences, not ratios of the dB numbers.
- Step 2: Difference = 100 − 85 = 15 dB.
- Step 3: Intensity ratio = 10 raised to the power (15 ÷ 10) = 10¹·⁵ ≈ 31.6.
- Step 4: So the concert carries about 32 times the sound energy of the traffic.
Answer: The concert is about 32 times more intense, not 18% more.
Common mistakes
- Treating decibels as linear. Every 10 dB increase is a tenfold increase in intensity.
- Listing only human hearing loss as an effect. Exam answers often want wildlife effects, like masked communication or disrupted migration.
- Forgetting the ocean. Ship and sonar noise in water is a major source of noise pollution for marine mammals.
On the exam
- Questions often ask for an effect of noise pollution on wildlife. Be specific: 'masks whale calls, making it harder to find mates or navigate.'
- Be ready to compare two decibel values using powers of 10, just as you do with pH.
Connected topics
Videos
Check yourself
4 questions on 7.8 Noise Pollution. Pick an answer to see if you got it, and why.
Shipping traffic has greatly increased low-frequency noise in the ocean. Which effect on whales is most likely?
Workers at a construction site are exposed every day to jackhammers producing about 100 decibels. Which is the most likely long-term effect if they do not wear hearing protection?
| Site | Average background noise (dB) | Minimum frequency of song (kHz) |
|---|---|---|
| Forest | 42 | 2.4 |
| Suburb | 55 | 2.9 |
| City center | 68 | 3.4 |
Hypothetical data from recordings of one songbird species
Which conclusion is best supported by the data?
Which experiment would best test whether noise itself causes the change in song pitch?
0 of 4 answered