When it comes to free cross-platform audio editors, Audacity is usually then one that is being mentioned or recommended. While the editor deserves to be mentioned first, thanks to its immense feature set and functionality, it may be overkill for a lot of users who just want to edit audio files quickly.
Ocenaudio may be an alternative for those users. It is also free and cross-platform but not as complex as Audacity is in many regards.
You can load one or multiple audio files via drag and drop or the file menu into the application. As far as audio format support is concerned, it seems to support all major and many lesser used audio formats which means that you should not run into any issues loading your files into the program unless they are stored in an obscure format.
Ocenaudio displays the waveform of the selected file in the interface afterwards. You can select part of the audio with the mouse, and if you hold down the Ctrl-key, make additional selections.
This multi-selection feature can be quite handy to preview and edit different parts of an audio file at once. You can also zoom in and out if you move the mouse over the editing area.
You can edit selected parts of the audio file directly, for instance by selecting Del on the keyboard which cuts it. This can be useful if you are editing a podcast or interview and want to cut out the silent parts of it.
As far as editing is concerned, Ocenaudio makes available quite a few options in this regard. Besides deleting parts of the audio easily, you can use copy and paste operations, undo changes, or manipulate the selection, for instance by inverting it.
Dozens of effects are made available by the application. From normalizing the audio file over filters to delays. These filters can be applied in real-time to the audio file to preview them right away.
The view menu of the editor displays several interesting options to add different view modes or change the current one. You can add a spectral view mode for instance or display both modes at the same time, display a full-size level meter instead of the small one that is displayed by default, or hide various interface elements such as the file sidebar.
Extra features such as the removal of all metadata, audio recording, the creation of iPhone ringtones, or the creation of audio screenshots complement the program nicely.
Processed files can saved in the original format or one of the other supported formats. If you do not make any changes to the audio file, you can use the program to convert formats as well.
Ocenaudio's biggest advantage over Audacity is that it is easier to use. While Audacity professionals may disagree with that, most users who never touched an audio editor in their life will probably fare better with Ocenaudio because of that.