Harmfulness of noise

The harmfulness of noise is related to a number of parameters. In its report “Health impacts of noise: Overview, noise-health indicators” (2004), the AFSSE points out the effects of the characteristics of the noise source, the context and individual factors that can interact.

- The quality of the noise: high-pitched noises (high frequencies) are, for the same intensity, more harmful than low-pitched noises.

- The purity of the noise: a pure sound of high intensity is more traumatising for the inner ear than a wide-spectrum noise. But bear in mind that pure sounds are not frequent in an industrial context or in the environment.

- The intensity of the noise: the risk of temporary or permanent hearing loss grows with the intensity. There is a limit below which no mechanical fatigue appears.
In these conditions, the ear can bear an almost infinite number of sounds. For example, lengthy exposures to noise levels below 70-80 dB do not cause any lesions. On the contrary, a very intense sound provokes an unpleasant, even painful sensation; 120 dB is the threshold of pain. Beyond 120 dB, the ear drums can suffer significant lesions, as well as the hair cells in the inner ear. The hair breaks with impulse noises over 130 dB(C).

- The emergence and the rhythm of the noise: a sudden and unpredictable impulse noise is more harmful than a continuous noise of the same energy.

- The duration of exposure: for the same sound atmosphere, the longer the duration of exposure is, the more significant the lesions of the inner ear will be. Successive professional and extra-professional (nightclubs, concerts, MP3 players...) exposures increase the duration of exposure, and consequently the risk of ear lesions.

- Individual vulnerability: age, history of ENT infections, history of head trauma, metabolic troubles or high blood pressure can increase the harmful effects of noise.

- Combination with other risk exposures: exposure to noise combined with vibrations and ototoxic chemical agents or drugs can increase the risk of acoustic trauma.