---
title: "Typical noise levels and effects of noise"
subject: "Environment and Pollution Control"
chapter: 6
key: "semester_7/environment_and_pollution_control:noise-levels-places-effects"
source: https://www.bctengineer.com/q/semester_7/environment_and_pollution_control/noise-levels-places-effects
site: BCT Engineering
---

# Typical noise levels and effects of noise

Environment and Pollution Control · Chapter 6: Noise pollution

- Asked in: year not given, 5 marks
- Video: [Effects of Noise Pollution - Faculty of Engineering & Technology](https://www.youtube.com/watch?v=jPwMD4PIh_Q) — SGT University
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/environment_and_pollution_control/noise-levels-places-effects
- Whole chapter: https://www.bctengineer.com/md/semester_7/environment_and_pollution_control/chapter-6

## Question

Give typical sound levels (in dB) at different places and activities. Explain the harmful effects of noise on human beings.

## Short answer

Typical levels range from 0 dB threshold of hearing, 20-30 rustling leaves, 55-65 conversation, 70-80 traffic, 85-95 factory, 110-120 aircraft, to 120-130 pain. Harmful effects include hearing damage, tinnitus, raised blood pressure, stress, annoyance, sleep disturbance, and speech interference.

## Answer

#### Typical noise levels
| Source / place | Level (dB) |
|---|---|
| Threshold of hearing | 0 |
| Rustling leaves, quiet bedroom | 20-30 |
| Library, quiet residential area at night | 30-40 |
| Normal conversation (1 m), office | 55-65 |
| Busy street traffic, restaurant | 70-80 |
| Heavy truck, factory, loud radio | 85-95 |
| Motorcycle, power tools, disco | 95-105 |
| Aircraft take-off at 100 m, thunder | 110-120 |
| Threshold of pain | 120-130 |
| Jet engine at close range, firecrackers | 140 |

Guideline values (WHO): about 55 dB(A) outdoors in the daytime in residential areas, 30 dB(A) bedroom at night. Industrial limit for an 8-hour exposure is typically 85-90 dB(A).

#### Effects of noise
1. **Hearing damage:** temporary threshold shift and permanent hearing loss from long exposure above 85 dB(A), or sudden very loud sound (acoustic trauma). Tinnitus (ringing in the ears).
2. **Physiological:** raised blood pressure and heart rate, stress hormone release, heart disease, headache, digestive disturbance.
3. **Psychological:** annoyance, irritability, anxiety, reduced concentration, fatigue.
4. **Sleep disturbance:** waking, poor sleep quality.
5. **Communication and performance:** speech interference, accidents, reduced work efficiency and learning in children.
6. **Other:** damage to buildings from vibration (e.g. sonic boom), and stress in animals.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Which ordering of typical sound levels is correct (lowest to highest)?
   A. Jet engine, busy street, library
   B. Library, normal conversation, busy street, aircraft take-off
   C. Busy street, library, conversation
   D. Aircraft take-off, conversation, library
   Answer: B. Library is 30-40 dB, conversation 55-65, busy street 70-80 and aircraft take-off 110-120 dB. (Key point: Typical levels)

2. Long exposure above roughly what level causes hearing damage?
   A. 40 dB(A)
   B. 55 dB(A)
   C. 85 dB(A)
   D. 20 dB(A)
   Answer: C. Temporary and permanent threshold shifts result from long exposure above about 85 dB(A); industrial 8-hour limits are 85-90 dB(A). (Key point: Hearing damage threshold)

3. Which is a physiological effect of noise besides hearing loss?
   A. Lower heart rate
   B. Raised blood pressure and heart rate with stress hormone release
   C. Improved digestion
   D. Improved sleep quality
   Answer: B. Noise raises blood pressure and heart rate, releases stress hormones and can cause heart disease and headache. (Key point: Non-auditory effects)

## Related in Environment and Pollution Control

- [Adding sound levels from several sources](https://www.bctengineer.com/question.md?key=semester_7%2Fenvironment_and_pollution_control%3Acombining-noise-levels-numerical) — Environment and Pollution Control, chapter 6
- [Nature of sound and the human ear](https://www.bctengineer.com/question.md?key=semester_7%2Fenvironment_and_pollution_control%3Asound-nature-human-ear) — Environment and Pollution Control, chapter 6
- [Sources and effects of SO2, NOx and CO](https://www.bctengineer.com/question.md?key=semester_7%2Fenvironment_and_pollution_control%3Agaseous-pollutants-so2-nox-co) — Environment and Pollution Control, chapter 1
- [Particulate pollutants: sources and effects](https://www.bctengineer.com/question.md?key=semester_7%2Fenvironment_and_pollution_control%3Aparticulate-pollutants-sources-effects) — Environment and Pollution Control, chapter 1
- [Water pollution: sources and effects](https://www.bctengineer.com/question.md?key=semester_7%2Fenvironment_and_pollution_control%3Awater-pollution-sources-effects) — Environment and Pollution Control, chapter 4

## Related in other subjects

- [CFCs in ozone depletion and harmful effects](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Acfc-ozone-harmful) — Engineering Chemistry, chapter 3
- [Sound absorption and noise control](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aabsorptive-materials-noise-control) — Building Technology, chapter 1
- [Water pollutants, harmful effects, control measures](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Awater-pollutants-effects-measures) — Engineering Chemistry, chapter 3
- [Typical voltage levels and why three-phase](https://www.bctengineer.com/question.md?key=semester_4%2Fpower_system_analysis_i%3Atypical-voltage-levels-three-phase) — Power System Analysis I, chapter 1