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Sound Level Meter Response Time
This button shows the name of the time response characteristic. The default names are Fast, Slow, Quasi-Pk, PPM, and Custom. Clicking on the button opens the SPL Response TCs dialog to allow a different response to be selected from among those already defined, or to define a new response and name as desired.
The response time is analogous to the damping of a conventional mechanical meter movement. It is usually desirable to slow the response of the display in order to obtain an average value when the signal is rapidly changing.
Usually when both Attack and Decay are used, Attack is set much shorter in order to respond to sudden changes. But since the human ear is less sensitive to very brief sounds, Attack is typically set to a non-zero value to deliberately reduce the response to such sounds. (Daqarta uses an Attack value of zero to disable the Response function, so the meter responds immediately to all changes.)
Note: The response time is independent of the meter display update rate, which is approximately 10 times per second. A small asterisk is shown to the left of the response time button on alternating meter updates. This assures you that the meter is in fact updating, even if the reading is unchanged due to a very stable signal.
For file data you can set a low Read Step Size in the DDisk Controls dialog and toggle Trigger off to get a "slow motion" playback of the file that still retains the specified response time dynamics. If you don't have a .DQA file recorded on a calibrated system, you can use a .WAV or other uncalibrated file by opening the User Line dialog and loading a calibration file, or by setting Units Name to "Pa" and setting the proper dB:Units/Volt, then toggling SPL on.
SPLresp=1 opens the SPL Response TCs dialog, SPLresp=0 closes it, and SPLresp=x toggles between open and closed.
Note that you do not need to open the dialog to change its controls directly via macro commands.
See also Sound Level Meter
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