Run MediaHuman Audio Converter application and press Add button on toolbar to add video file (MP4 video in our example). Or you can simply drag'n'drop some files or folders from the file manager on the main window.
Now you need to select MP3 as an output format. To do it press the corresponding button on the toolbar and select the format from the appeared dialog.
You can select among predefined MP3 settings or set up your own by choosing Custom menu item.
Now we are ready to start the conversion. Press the last button on the toolbar and wait until it is processing. If you've changed your mind press it again to stop the conversion.
It is done. You can locate the extracted audio file pressing the Locate button on the video item.