Week 6 - People

Excessive exposure to noise causes loss of hearing.

The most damaging type affects the Inner Ear – the Cochlea which contains nerve endings that connect to the brain and provide our sense of ‘hearing’.

• Temporary Hearing Loss – (Temporary Threshold Shift) - Ok if you allow 48 hours for recovery
• Permanent Hearing Loss – (Permanent Threshold Shift) from exposure every day. Eg bar staff, construction staff. This loss is permanent.

All hearing losses are added to the continuous hearing loss that accumulates with age – from the time of birth!

Noise factors to measure

1. Energy level - The hearing system reacts to the Sound Pressure Level (SPL) usually measured in decibels (dB)

2. Frequency structure

Some frequencies are more annoying or harmful than others

Eg: high whining frequencies

3. Time Duration

Short periods of noise are less likely to annoy than prolonged exposure

Sound Levels

Decibel (dB) scale used to –

•   give a manageable scale of numbers
•   match the non-linear response of human hearing

The decibel is a logarithmic ratio of two quantities

- Usually measured in terms of pressure