MIL-HDBK-1908B
Q
Lavg = log102 log10
T
1 2L(t)/Q dt
T
0
where: T = total time in hours t = varying time
L(t) = the time varying A-weighted sound pressure level
Q = exchange rate, usually 3, 4, 5, or 6 dB.
The Lavg value can be calculated from the following alternate expression when the sound level takes on a sequence of N constant levels, Li, each lasting for a time period of Ci hours:
where: D=
Lavg 85
Ci
Q
log10
8D
log10
2 T
i 1 Ti
Ti = Limiting exposure time at each A-weighted sound pressure level = Li = ith A-weighted sound pressure level.
The exchange rate must be specified when referring to Lavg.
Toggle switch gen/acq. A lever operated control with discrete positions.
8
2(Li-85)/Q
Total daily exposure (TDE) snv. The ratio of actual daily noise exposure to allowable daily noise exposure.
Touch pad uci. A control device that allows the user to control cursor movement in any direction by moving the finger across the top of a touch sensitive pad.
Touch screen uci. A control device that allows the user to communicate with the computer by touching the screen. Touch screens can be operated using two different strategies: (1) The first contact strategy actuates the point at which the operator makes contact with the display screen; (2) the "last contact" strategy actuates the point at which the operator withdraws his/her touch from the display screen.
Trackball uci. A control device with which the user can control cursor movement in any direction by rotating the ball. Trackballs are especially useful when it is desirable to move the cursor long distances quickly.
Transaction uci. An action by a user followed by a response from the computer. The term is used here to represent the smallest functional "molecule" of user-computer interaction.
Transient sounds snv. Sounds that occur during turn-on and turn-off of the equipment and infrequent sounds that are less than 15 seconds in duration. If sounds occur at intervals of 1/2 second or less, the sound is considered steady-state sound.
Transillumination gen. Light passing through a diffusing element to be viewed, e.g., the illumination produced by edge- or back-lit sources that make translucent console panels or indicators
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