Calibrate Exported Samples

Introduction

Starting with Raven Pro 1.6.1 the formula for calculating power density and the default power density scale changed compared to Raven Pro 1.5. However, when the user exports samples from a spectrogram, selection spectrum, or spectrogram slice view, the exported values use the the Raven Pro 1.5 power density calculation and scale.

The protocol below shows how to calibrate exported samples from a spectrogram slice view. The same principles apply to spectrogram and spectrogram slice views.

How to Calibrate Exported Samples in the Selection Spectrum View

The attached Excel worksheet demonstrates how to calibrate on exported selection spectrum such that the exported values are equal to those displayed in the selection spectrum view in Raven Pro 1.6. This demonstration assumes that the “Match Raven 1.5 POWER measurements” preference is not enabled.

2000Hz.Selection Spectrum

To re-create this demo worksheet:

1. Open “2000Hz.aif” in the Examples folder.
2. Open a new selection spectrum view.
3. Commit a selection in the waveform view that extends from the beginning to the end of the sound file.
4. Click on the left end of the selection spectrum view to activate it. There should be a blue vertical bar on the left end of the selection spectrum view.
5. Select “Export ‘Sound 1’ Selection Spectrum 1 Samples” from the File menu.
6. Calibrate Raven, noting the Calibration Constant. You will need this later.
7. Open the exported selection spectrum view and save it in xlsx format.
8. Add the following parameters to the top of the worksheet.
   1. Calibration Constant from step 6.
   2. Reference Pressure for recordings in air, 0.00002 Pa.
   3. DFT Size, 512 samples. DFT Size is one of the spectrogram parameters, and 512 samples is the default in Raven.  See Appendix B in the Raven Pro User’s Manual.
   4. Sample Rate, 22050 Hz. This is a part of your sound file format, which Raven displays in the Information side bar.
   5. Grid Spacing, Sample Rate / DFT Size. See Appendix B in the Raven Pro User’s Manual.
9. Add a column converting uncalibrated decibel PSD to uncalibrated PSD on a linear scale, for example, “=10^(A9/20)”.
10. Add a column multiplying linear PSD by the calibration constant, for example, “=$A$2*B9”.
11. Convert PSD (Pa/Hz) to PSD (db/Hz re: 20 µPa), for example, “=20*LOG10(C9/$A$3)-10*LOG10($A$4)”.