dB Relative / User Units

Macro: Atn_dB

This control is only enabled when Use dB is active, which requires that your sound card be calibrated. It is located at the bottom of the Attenuator Options dialog.

By default this button is set to 'dB Relative'. The Generator dB controls are then relative to the maximum sound card output, so 0 dB is loudest and all softer outputs are progressively more negative from there.

But you can perform an absolute range calibration so that Daqarta knows the actual output voltage. If you then enter a Units/Volt factor in the relevant User Line dialog or load a Spkr.CAL file (or .FRD) in that dialog, Daqarata can convert the output voltage to absolute units like SPL. The Y axis and cursors will automatically show those units whenever User Units is active. If you also want the Generator controls to use those units, set this button to 'dB User Units'.

Note that absolute sound measurements are specific to your whole system setup; if you want the calibration to remain valid, you must not change anything other than the volume. In particular, you must not change the signal waveform or frequency, any external amplifier settings, or the distance or angles between the speaker and ear or unit under test.

Macro Notes:

Atn_dB=Usr or Atn_dB=1 sets dB User Units, Atn_dB=Rel or Atn_dB=0 sets dB Relative, and Atn_dB=x toggles between the two.

Note that this command is enabled only when Use dB is active. Otherwise, the macro may abort with an error message. To be safe, give UseCal=dB before Atn_dB.

See also Generator Attenuator Options Dialog.