Discover the new maintenance brush

As and from 1st May 2012, all Original White hearing protections will be supplied with a maintenance brush in addition to instructions for use.

It allows removal of:

• ear wax accumulating inside the protection drilling using the "Extract" part
• external contamination using the "Brush" part

Download the instructions for use (PDF - 2.8 Mo)

Definition of noise

Understanding noise to combat it more effectively

Defining noise objectively:

Noise is a physical phenomenon of mechanical origin involving a (very slight) variation in pressure, vibratory velocity or density of the fluid, which spreads while gradually changing the state of each element of the medium in question, thereby giving rise to a sound wave. The spreading of the circles in water following disruption of the surface provides a good illustration of this phenomenon.

Defining noise subjectively:

Noise is a sensation aroused by a sound wave, which is perceived by the ear and is subsequently transmitted to the brain where it is decoded.

Noise level

The level is the first element that characterises noise. It corresponds to the sound volume and is physically measured in decibels (dB) using a sound level meter. In order to take account of the level actually perceived by the ear, a physiological decibel is used: the decibel A, dB(A). The audibility threshold is set at 0 dB(A) and that of pain at 120 dB(A). It must be realised that:

• the noise level decreases with distance. Hence, the noise level measured at 100 dB(A) at 1 m decreases to 94 dB(A) at 2 m and 88 dB(A) at 4 m.
• when several sound sources are present, the level does not follow a mathematical progression equal to the number of sources, but progresses by increments of 3 dB(A).
  Example:
  1 pneumatic drill = 90 dB(A)
  2 pneumatic drills = 93 dB(A)
  4 pneumatic drills = 96 dB(A)
• if the level of one sound very greatly exceeds that of another, the latter cannot be heard. A portion of the acoustic information is lost or misinterpreted, thereby resulting in risks of accidents.

Noise frequency

Frequency is the second element that characterises noise. It corresponds to the number of oscillations per second and is measured in Hertz (Hz).

• the greater the rapidity of the variations, the greater the frequencies and the higher the pitch of the sound.
• if the variations are slow: the frequencies are low and the sound is more low-pitched in this case.

The human ear is capable of hearing a range of sound frequencies:

• from very low (20 Hz)
• to very high (20 000 Hz)

The frequencies that our ear cannot hear are:

• infrasounds (frequencies of less than 20 Hertz)
• ultrasounds (frequencies exceeding 20 000 Hertz).

Duration of noise:

The duration of a noise is a crucial element for its perception and the discomfort or pleasure that it causes, without forgetting its level which may vary over time. A single measurement is not enough in order to assess the level of a noise. The LEQ measures the discomfort caused by a noise and quantifies the noise dose received over a given time (mean intensity).

Awareness-raising among your employees

Backed by 10 years of experience, COTRAL Laboratory offers training programmes hosted by a prevention technician in order to explain to your employees:

• what noise is
• how its impact can be reduced by means of customised hearing protections

Contact-us to determine the offer that suits you.