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Sound pressure level (SPL) - Given in decibels (dB), it is 20 times the logarithm to the base 10 of the ratio of a given sound pressure to the reference sound pressure, which is 20 micropascals (mPa) for airborne sound. The sound pressure is the root mean square value of the instantaneous sound pressure over a given time interval.

dB(A) – Unit of measurement for sound levels, “A” weighted to measure response the same as the human auditory system.

Exposure action value – Levels of noise exposure that must not be exceeded.

Hearing protection – personal protective equipment designed to reduce noise entering the ear.

Competent person – An individual appropriately trained to carry out suitable and sufficient noise risk assessments.

1/3-octave band - The interval between two frequencies whose ratio is 21/3:1. These frequencies define the edges of the band. Normally, the band is referred to by its band centre frequency, which is the geometric mean of the two edge frequencies. For upper sonic and ultrasonic frequencies the bands have been designated as the 10, 12.5, 16, 20, 25, 31.5, 40 and 50 kHz bands.

Ultrasonic - Utilizing, produced by, or relating to, ultrasonic waves or vibrations. For the purposes of this document, ultrasonic waves are acoustic waves having a frequency above 20 kHz.

Upper sonic - Utilizing, produced by or relating to upper sonic waves or vibrations. For the purposes of this document upper sonic waves are acoustic waves in the frequency range between 10 and 20 kHz.