PHYSICS · Stage 9 · Chapter 13: Sound Waves
Physics 13.3 Hearing, decibels, and risk — Decibel Scale and Noise-Induced Hearing Loss
5 min read 6 parts Lesson 3 of 5
Lesson summary
Physics 13.3 Hearing, decibels, and risk — Decibel Scale and Noise-Induced Hearing Loss — Alhussan International Academy — Physics (Stages 7–9) notes: Name the unit of sound intensity and describe the risks of loud sounds and how to reduce them.Intensity — The loudness of a sound…
- Not like a ruler
- Loudest possible
- Sudden loud sounds
- Long exposure
- Reducing risk
- Decibel meters
Part 1 of 6The decibel scale
- Intensity — The loudness of a sound is measured with a sound-level meter on the decibel (dB) scale.
- Noise = sounds that we do not want to hear.
- Not like a ruler — Every increase of 10 dB increases the intensity 10 times.
- A 40 dB sound has 10 times the intensity of a 30 dB sound.
- A 50 dB sound has 100 times the intensity of a 30 dB sound.
- Loudest possible — The loudest possible continuous sound is 194 dB; explosions and earthquakes can be louder but do not last.
Part 2 of 6Typical sound levels
| Sound | Approximate level |
|---|---|
| Threshold of hearing | 0 dB |
| Quiet whisper | 30 dB |
| Normal conversation | 60 dB |
| Busy road | 80 dB |
| Chainsaw, can damage hearing after about 8 hours a day | 90 dB |
| Rock concert, loud headphones | 100 to 110 dB |
| Vuvuzela, painful | 120 dB |
| Jet engine nearby | 140 dB |
Part 3 of 6Hearing damage
- Sudden loud soundsThey can burst the eardrum.
- Long exposureIt damages the tiny hair cells in the inner ear, which do not grow back, causing permanent noise-induced hearing loss.
- TimeThe risk depends on both the loudness in decibels and the length of time of exposure.
Part 4 of 6Understanding risk
- Risk — It combines the probability that something bad happens with the consequence if it did.
- Examples — An aeroplane crash has serious consequences but a very low probability.
- Listening to loud music may not seem risky, but the probability of hearing damage rises the longer you listen.
- Reducing risk — A risk can be reduced by lowering the probability or the consequences.
Part 5 of 6Reducing the risk from noise
- ShieldingPut something between the sound source and your ears, such as ear defenders.
- DistanceMove away from the source of the sound.
- TimeReduce the time spent near the source.
- Decibel metersPeople can use them to monitor sound levels.
- HeadphonesLower the volume, take breaks and use noise-cancelling headphones so the volume does not need to be raised.
Part 6 of 6Protecting hearing at work
- Ear defenders — They reduce the intensity of sound reaching the ear.
- Construction workers using drills, airport ground crew, factory workers and musicians should wear them.
- Other risks — Tiredness from long periods of driving also raises the probability of accidents.
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