9/29/09 Using ID Setting Files 7-39Intv Threshold - (LOG, SSA) Intv Threshold sets the threshold for computing the intervaltime weighted average (TWA). As per the requirements ofvarious regulatory agencies, only those sound levels whichare above a certain threshold level are used when computingthe TWA. Accordingly, this setting can take on any integralvalue within the following range:0 to 255 dBFor hearing conservation measurements, set the threshold to80dB. For most community noise measurements, set thethreshold to 0dB.Intv Exchange - (LOG, SSA) The Intv Exchange sets the exchange rate (sometimes calledthe “doubling rate”) that is used to calculate the intervalTWA. The exchange rate reflects the relationship betweenthe permitted exposure levels and the exposure duration.Selecting an exchange rate of 5dB, for example, means that5dB may be added to the permissible exposure level everytime the exposure duration is cut in half. This settingprovides the following four options:3dB - The 3dB (default) option is the most com-monly used and results in the L eq time weighted aver-age which is used in Europe and for measurementsthat comply with U.S. Environmental ProtectionAgency (EPA) regulations.4dB - The 4dB option results in the L DOD timeweighted average which is used for measurementsthat comply with U.S. Department of Defense (DOD)regulations.5dB - The 5dB option results in the L OSHA timeweighted average which is used for measurementsthat comply with U.S. Occupational Safety andHealth Administration (OSHA) regulations.6dB - The 6dB option results in the L Avg timeweighted average which is merely a convenient rep-resentation of the long-term average noise level asopposed to the RMS noise level.Intv Spectrum - (SSA only) The Intv Spectrum allows you the choice of storing spectraldata with the interval. It will always give you the Leq
