What are the (3) 'exchange rate values' corresponding to the doubling of sound pressure levels when two machines have a sound level of 85 dB(A)?

• A. DoD: +3 dB; OSHA: +5 dB; ACGIH: +3 dB
• B. DoD: +5 dB; OSHA: +3 dB; ACGIH: +3 dB
• C. DoD: +3 dB; OSHA: +3 dB; ACGIH: +5 dB
• D. DoD: +3 dB; OSHA: +5 dB; ACGIH: +3 dB

Answer: (D)

The concept at play is how exposure time is adjusted when noise levels change, which is captured by the exchange rate. When two identical noise sources are present, the overall sound level increases by about 3 dB (two equal sources double the sound energy, and a 3 dB rise corresponds to a doubling of energy). So two machines at 85 dB(A) would mix to about 88 dB(A).

Different agencies specify different steps (exchange rates) for adjusting permissible exposure time as the level rises. DoD and ACGIH use a 3 dB exchange rate, meaning every 3 dB increase halves the allowable exposure time. OSHA uses a 5 dB exchange rate, so a 5 dB increase halves the allowable exposure time; smaller increases like 3 dB do not trigger a halving under OSHA.

Therefore, for this scenario, the exchange rate values are: DoD +3 dB, OSHA +5 dB, and ACGIH +3 dB.