Data AcQuisition And Real-Time Analysis
Scope - Spectrum - Spectrogram - Signal Generator
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Science with your Sound Card!

Sound Card Sound Level Meter Screen Image

[Daqarta Sound Level Meter (45K image)]

The Sound Level Meter is shown positioned near the top of the main Daqarta window. Like the Voltmeter and Frequency Counter, it can be positioned anywhere on the screen, and the size of the display font changes when you resize the meter by dragging its borders. You can fill the screen for a really big readout that can be seen from across the room.

The meter is using A-weighting, selected from the Curves dialog at the right. The dialog was invoked by hitting the Weighting button on the meter, which is always labeled with the current weighting curve, or "Flat" if there is no weighting.

The Response Time button is labeled with the current response, which here is "Fast". Hitting the button invokes the dialog shown below the meter, which allows selection of preset responses, or editing them to create new ones. With only an Attack value (as in the Fast response shown here), it behaves as a simple time constant. Setting Decay as well produces a quasi-peak response.

Next to the "Flat" button on the meter are the Peak and PeakTC buttons. The meter continuously monitors peak values, with and without response time constants, since the last Reset. These buttons only select the display mode; you can toggle them on or off to see peaks or current SPL with no effect on the held values.

The Places control allows selection of 0 to 5 decimal places for the reported SPL, currently set to 1.

Note that 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 frequency response and sensitivity are specified via a CAL file, which is loaded into the User Line Dialog for the input line you are using.



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