Spectrum mode
The spectrum mode allows you to watch your signals' power spectra, easily switching between them.
Thanks to an intractive interface, you can select the location to show, watch different epochs and verify any variation during the time, change the corresponding time window and focus on any frequency band.
First of all, in the following interface you have to select the directory which contains all your signals.
Here you can insert the name of the directory (with its path) in the text box, or search it on your computer through the button next to it.
Note that if you have switched between study modalities, for example if you computed a guided study or if you used it before in the same session, you will find the previously setted data directory in the text box, so you can change or use it again.
Now you can push the Next > button and go to watch your signals.
In the following interface you can watch the first of the signals' power spectrum related to the data files contained in your data directory.
Here, you can see the power spectrum, initially of the first location, plotted in a semilogaritmic plane, where the x axis represents the frequency values (in Hz), while the y axis represents the power values (in dB, equal to ten times the logarithm to base 10 of the power value, so 10*log(P)).
Let's learn how this interface works
To switch between signals' spectrum you can use the < Previous button to show the previous case, or the Next > button to show the following one.
Otherwise, it is possible to select a specific time series, through the 👤 button on the toolbar.
To manually translate forward and back the time series, you can use the arrows buttons.
Here, you can go a second or an epoch forward or backwards with the internal buttons or to the external ones, respectively.
In this case an epoch is intended as the same amount of time as the one showed by the interface.
You can also continuously and automatically go forward and backwards in time by pushing the arrows button in the toolbar of this interface.
Through the toolbar you can also show a chosen istant of time, go to the end of the signal or to its beginning, and whatch the related power spectrum.
You can choose the amount of time used as time window, which will correspond to an epoch when you forward and backwards in it, as well as the showed location.
You can always change the minimum frequency and the maximum frequency which have to be shown, and change them whenever you want.
Normally, Athena is able to read the necessary information, such as sampling frequency and locations relative to each record, automatically from the file of each signal.
If some of them are not inside the data file, you can always set them through the respective buttons in the toolbar.
In particular, for the locations list an external file will be required, while for the sampling frequency just enter its value.
Finally, if you need some information can always use the help button, which will open this wiki in a web browser.
The power spectra are computed through the Welch's power because of its advantaged with respect the FFT (Fast Fourier Transform).
Essentially, this method slices the original signal in several windows, which can be overlapped or non-overlapped, and averages the spectra of these.
This Welch's method is able to smooth over non-systematic noise, so it shows more robustness to noise than the FFT, and it is also less sensitive to some non-stationarities, even if it has a reduced spectral precision.
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).
Some shortcuts are also provided by this interface, listed in the related page of the wiki.
When you have finished analyzing visually the power spectra, you can immediately start to perform a study with the pipeline offered by Athena, or perhaps continue the visual analysis in the frequency domain.
So go back to the initial interface and start your study right away!