Plugin¶

Setup¶

The Psophometer Plugin is included with every OXYGEN installation, starting with OXYGEN R3.5.1

Please note that a dedicated plugin license is required for the calculation option to be visible.

Usage¶

Select one or more channels as inputs for the Psophometer calculation.

Please note that input channels must have a sampling rate of 20 kHz or higher.

Fig. 1 Channel list with multiple selected channels¶

Then open the “Add Channel” dialog by pressing the plus button.

A dialog opens where the Psophometer frequency-weighting settings can be configured (see Fig. 3 ). The newly created Psophometer calculation group can be assigned a custom name.

Fig. 2 Add Channel dialog showing Psophometer options¶

Fig. 3 Channel list showing new Psophometer calculation group¶

The channel details view is used to modify each channel’s settings individually and for detailed preview.

Fig. 4 Channel details setup of calculation channel¶

Psophometer calculations are then available as math channels.

Fig. 5 Sidebar channel list showing the calculated Psophometer channels¶

Calculation¶

The calculation is based on an FFT analysis. Depending on the input sampling rate, the FFT block size is chosen to be 2ⁿ samples while the time window stays between 75 and 125 ms, to ensure compliance with the detector circuitry tests (see ITU-Recommendation O.41 (10/94) )

Table 2 Sampling rate and FFT block size¶
Sample rate	FFT block size
20 kHz	2048
50 kHz	4096
100 kHz	8192
200 kHz	16384

Weighting options¶

Different weighting options are available:

ITU-T O.41¶

Fig. 6 Telephone circuit Psophometer weighting coefficients and limits¶

C-Message¶

Flat¶

Unweighted¶

Comparison between Psophometer and C-Message Weighting¶

Fig. 10 Comparison between Psophometric and C-message weighting¶