Changes to Power and Power Density Measurements in Raven Pro 1.6

In Raven Pro versions up until Raven Pro 1.6, Raven Pro reported the power spectral density in units of power in decibels. Starting with Raven Pro 1.6, we have switched to reporting the power spectral density (PSD) in units of dB/Hz. This is a more customary unit for power density, since it facilitates the comparison of values across spectrogram parameters. In Raven Pro 1.6 power spectral density (dB/Hz) is equal to the Raven Pro 1.5 value (dB) minus10 times the base 10 logarithm of the DFT size used to generate the spectrogram. This means that reported power density will change when you change the DFT Size. The names of power density measurements have changed to emphasize that the calculation has changed, and to emphasize that these measurements are power density measurements, not power measurements.

Another change with Raven Pro 1.6.1 is the default power reference. Raven Pro 1.5 used an arbitrary value of “1” as reference, while Raven Pro 1.6.1 uses decibels relative to full scale (dB FS), a scale in which zero is defined as the highest sound amplitude that can be recorded with your recording system in its current configuration. As a result, most dB FS measurements are negative. The dB FS is unit is familiar to sound recordists, and its use reminds the user that reported power and power density values are uncalibrated.

The user can change the formula and scale of power and power density values several ways:

• Enable the preference named “Match Raven 1.5 POWER measurements”.
• Disable the preference named “Report POWER measurements and axes in dB re full scale”.
• Calibrate the signal.

The “Preferences” and “Calibrate” dialogs can be opened from the Edit menu.

Note that in Raven Pro 1.6 exported spectrogram and spectrum samples, as described on pages 178 – 179 in the Raven Pro User’s Manual, are calculated using the Raven Pro 1.5 formula for power density.

More details about power and power density measurements can be found in New Measurements.