Controls: Options >> Sound Level Meter
Macro: SPLdlg

The Sound Level Meter is a dialog that can be invoked from the Options Menu or toggled open or closed directly via CTRL+L.

The meter allows selection of standard or custom weighting curves and response times, as well as two different continuous peak hold modes and adjustable number of decimal places.

• Channel (L.In, R.In, L.Out, R.Out)
• Weighting Curve
• Response Time
  • Select (Fast, Slow, Quasi, PPM, Custom)
  • Name Edit
  • Attack
  • Decay
• Peak / PeakTC Hold
• Peak Reset
• Decimal Places

In order to use the Sound Level Meter to measure SPL, your system must first be calibrated. Auto-Calibration allows Daqarta to keep track of relative sensitivity when you change Input levels, and Full-Scale Range calibration gives an absolute voltage sensitivity for each Input line.

In addition, you must use a calibrated microphone. The sensitivity of the unit is specified in the Units/Volt setting under the User Line Dialog for the Input line you are using, and Units Name must be set to 'Pa' (Pascals).

Normally, the frequency response of the microphone is specified via a CAL file which includes Units/Volt and Units Name.

The SPL button next to the Units Name must be active, which requires Y-log Spectrum or Sgram mode.

When you activate the Sound Level Meter dialog, Daqarta automatically sets Y-log Spectrum mode and toggles User Units on, as needed. That process does not attempt to set a specific Input line, load a CAL file, or enable that line to use SPL. However, all of these states are retained across sessions, so you only need to set things up for SPL measurements once, and they will be correct as long as you don't change them.

If you later toggle any of these settings off while the Sound Level Meter is open, its display will change to show 'No Spect', 'No Ylog', 'SPL Off', or 'Uncal' until you restore the required mode.

In general, you should avoid the sound card's microphone input line, since internal Mic preamps are typically noisy and have poor frequency response. Instead, use a separate microphone preamp to drive the card's Line In connections.

Note that although the Voltmeter dB option can also read SPL, it does not include frequency response information from the CAL file, nor from weighting curves. It also uses only a simple single time constant scheme that is not automatically adjusted for true time in msec like the Response calculation of the Sound Level Meter. You may nevertheless find the Voltmeter useful as a second SPL channel in certain cases where you can compensate for these differences.

Besides measurements on live signals, you can also apply the Sound Level Meter to .DQA files created on a calibrated Daqarta system.

The Sound Level Meter dialog can be positioned by dragging its title bar in the usual Windows manner. The position and size will be maintained independently from other Daqarta dialogs, and will be saved across Daqarta sessions.

Unlike most Daqarta dialogs, the dialog size can be changed by dragging its borders. The numerical display font will be scaled proportional to the height of the dialog, allowing creation of extra-large displays for distant viewing. (On the initial use, you may need to adjust the size for your screen.)

Note: To copy the Sound Level Meter displayed value to the Windows Clipboard, left-click anywhere on the display. This captures a copy of the current value and pops up a message box allowing you to save it to the Clipboard.

Macro Notes:

SPLdlg=1 opens the Sound Level Meter dialog, SPLdlg=0 closes it, and SPLdlg=x toggles between open and closed.

• Back to Macro Load File
• Ahead to Sound Level Meter Channel (L.In, R.In, L.Out, R.Out)
• Daqarta Help Contents
• Daqarta Help Index
• Daqarta Downloads
• Daqarta Home Page
• Purchase Daqarta

Questions? Comments? Contact us!