TF mode

The TF mode allows you to perform the time-frequency analysis on your signals, chosing the location, the frequency band and the time window to analyze.

The time-frequency analysis allows to study the time series as two-dimensional objects, joining the time and the frequency domain rather than analyze them separately.

In particular, this analysis may be useful to determine if there are changes in the frequency domain of the signal during the time, because the analysis computed in the Spectrum-mode is easily interpretable only for signals which are stationary during the analyzed time window (classical Fourier analysis assumes that signals are infinite in time or periodic), while they may change substantially during this time segment.

Here, it is possible to choose between the logaritmic and the linear frequency scale.

These representations are equivalent, and the related analysis give the same information, even if in general:

• The logaritmic scale allows to easier analyze the lower frequencies
• The linear scale allows to easier analyze the higher frequencies

By using the related function (through the time_frequency_analysis.m file), it is also possible to change the number of wavelet cycles to use in order mediate between the temporal and the spectral precision.

In particular, increasing the number of cycles means a better spectral precision, but a worst temporal precision, so Athena uses as tradeoff a variable number of cycles, of which it is possible to select the minimum (3 by default) and the maximum (10 by default).

This mode also allows to use some speech commands by pressing the spacebar (you can find the list of commands in the speech command page of the wiki).

Now, you can start to anayze your signals, or return to the initial interface in order to select other modes.

Furthermore, if you need help in any step, you can push on the logo figure, which will open the documentation of the toolbox through a web browser.