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Q factor

TWA Equal noise exposure combinations
dB(A) Q = 3 Q = 4 Q = 5
100 48 min 1.41 hr 2 hr
99      
98 1 hr 2 hr  
97      
96 2 hr    
95     4 hr
94   4 hr  
93 4 hr    
92      
91      
90 8 hr 8 hr 8 hr

The number of decibels considered to double (or half) the risk of hearing damage in the workplace. A Q factor of 3 dB represents the equal energy principle and is based on the measured Leq value. A Q factor of 3 is recommended by certain US bodies such as NIOSH and the ACGIH and is mandated in European style noise regulations. A Q factor of 4 dB is mandated in certain US Department of Defense noise exposure regulations. The US OSHA regulations require a Q factor (or doubling rate) of 5 dB such that a noise is considered to be twice as risky (for the same exposure time) if it increases by 5 dB. The table above shows equal noise exposures for the main Q factor and noise level combinations.

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