Noise measurements provide false sense of security

The so-called A weighted noise measurement in dB has been the official standard for measuring noise in the workplace since the 1950s. But these measurements underestimate the power of certain types of noise which may cause hearing loss, according to researchers from Ã…lborg University in Denmark.

Short noise peaks from rattling bottles, compressed air blasts, and metal on metal noises are among the types of noises that the researchers found the standard noise measuring method unfit to record.

New method needed
The common noise measuring method has three shortcomings:

• Treble noises are recorded at the same levels as base and middle tones, yet treble noises are more damaging to people's hearing.
• Brief noise peaks are systematically adjusted to lower values even though noise peaks can be extremely damaging to people's hearing.
• Noise emanating from a front angle is given the same value as noise from other directions, even though the ear is more sensitive to such noise.

The current method of noise level recording was designed to provide indications of how the noise is perceived rather than how damaging it is to the ears. Because of this, the researchers recommend that new and improved methods for measuring noise in the workplace should be developed.

Source: Hørelsen, Landsforeningen for bedre hørelse, nr. 10, December 2005