Impulse noise: Comparison of dose calculated by 5-dB rule and 3-dB rule

In the past several years, there have been many proposals concerning incorporation of impulse noise into total worker exposure. This is a problem of particular concern in the United States as a consequence of the 5-dB trading rule mandated by regulation. The alternative approaches to integrating impulse noise are to use a direct integration with a 5-dB trading rule, to use a 3-dB rule SLOW integration according to ISO 1999 and the proposed ANSI standard for high level signals above 120 dBA or to use a 5-dB SLOW integration as performed by the ANSI Standard (S1.25) personal noise dosimeter. Simulation of each of these approaches with industrial noise data was performed. The effect of integrating high level transients with a 3-dB rule (p2) integration compared with a 5-dB rule (p1.2) integration is that the calculated dose is 3 to 15 times greater than the 5-dB rule dose. We would infer from this that substantially greater numbers of workers would be protected (or more sites would be in noncompliance) by using a 3-dB rule for impulse noise. Because of this, it is critical that a rigorous scientific basis be established for impulse noise dose prior to defining procedures for such dose determination.