Physical and Psychological Health
Noise, vibration and radiation can quietly damage the body over years, while mental ill health, violence and substance misuse harm people through the mind and behaviour. This element explains how each hazard hurts, when to assess it, and the controls that work.
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5.1 Noise
The physical and psychological effects of exposure to noise
Loud noise can cause permanent hearing loss, and neither surgery nor a hearing aid can reverse it. The effects on the body can arise directly or indirectly from the exposure. Noise-induced hearing impairment can take several forms:
- a temporary change in hearing, with a feeling that the ears are blocked
- temporary hearing loss and auditory fatigue
- tinnitus, which is a hissing, ringing or buzzing in the ears or head
These short-term effects may fade within minutes or hours after leaving the noise. Repeated exposure to loud noise, however, can lead to permanent tinnitus, permanent hearing loss or both.
Prolonged loud noise can also trigger anxiety and stress, and the longer the exposure continues, the more sensitive a person becomes to stress. People in high noise may feel irritable, frustrated or angry, and the effect on mental health grows stronger when they feel unable to control the noise around them. Noise can also reduce the depth and quality of sleep, which in turn affects mood and the ability to concentrate.
The meaning of commonly used terms
These basic terms are used when noise exposure at work is measured and assessed.
Sound pressure. The average variation in atmospheric pressure caused by a sound. The term may be preceded by other words such as instantaneous, maximum or peak, as in peak sound pressure. The sound pressure level (SPL) is the pressure level of a sound, measured in decibels (dB).
Sound intensity. Also called acoustic intensity. It is the power carried by sound waves per unit of area, in a direction at right angles to that area. Its SI unit is the watt per square metre (W/m²).
Sound frequency. Sound waves travel to the ear by alternately compressing and stretching the medium, which is usually air. The number of complete waves produced in one second is the frequency. If five complete waves are produced in a second, the frequency is 5 hertz (Hz), or 5 cycles per second.
The decibel scale. The decibel is a logarithmic unit that expresses the ratio between two values of a physical quantity, often power or intensity. When one of the two values is a fixed reference, the decibel can express the absolute level of the quantity, as it does for sound pressure.
Noise is measured in decibels (dB). Two frequency weightings are in common use:
- A-weighting, written dB(A), is used to measure average noise levels. It follows the sensitivity of the human ear at low levels and predicts the risk of damage to the ear quite well, which makes it the most widely used scale. A sound level meter set to A-weighting filters out much of the low-frequency noise, much as the ear does.
- C-weighting, written dB(C), is used to measure peak, impact or explosive noises. It follows the sensitivity of the ear at very high noise levels. The C scale is fairly flat, so it includes much more of the low-frequency range than the A and B scales.
Summary notes for Element 5 · Cheat sheet · Glossary. A study aid, not published or endorsed by NEBOSH.