Audacity is a GUI based tool. It is an open-source audio editor and recording application software.
Audacity is available for Windows, macOS & Linux. You can download Audacity from its official site, or in Ubuntu, you can download it from the Ubuntu store.
Audacity can be used from the command line or by directly clicking the icon in applications.
$ audacity <file_name>
Audacity displays the audio files in a wave form. You change the waveform into spectrogram by changing the layer into spectrogram. You can do it by clicking the arrow next to the track name to switch from waveform to spectrogram.
Spectrogram is a visual based view of representing the signal strength, or “loudness”, of a signal over time at various frequencies present in a particular waveform.
There are so many effects like changing speed, pitch, tempo etc. By clicking the effects option in the menu bar, you can see many options, and users can apply the effect only in the selected area or the entire track.
In CTFs we come across quite a few audio challenges. Mostly, these challenges are mainly about changing the layer to spectrogram or they embedding some data in morse format.
Morse Code means converting the text into Dot-Dash format. You can use this link for decoding that morse code. If you hear the audio has beeps, it is confirmed that, the audio file contains a morsecode you can directly upload that in this link and get the message you wanted. In CTFs we get challenges which have the morse code or we see that morse code after changing the layer to spectrogram.
An example for changing the layer to spectrogram,
An example for changing the layer and getting the morse code, You can see some extra data above the separation of two tracks, that is nothing but morse. Big lines represent Dash and Small lines represent Dot, the space between them separates each letter. If you want a clear idea of each and every letter you can separate it with / or |.
The morse code for alphabets and number is as follows,
For more information about morse code and usage of Audacity,