In Kotobee Author, you can add audio elements that can be played directly inside the page. In the case that the ebook is opened in a web browser, the browser's default audio player is used to play the audio file. The controls that appear (play, pause, stop, etc) are the ones which are equipped with the default browser.

To add an audio element

Click on the Audio tool in order to add an audio to your ebook.

One of the options of adding audio files is linking to a file already hosted online (the supported file format is MP3). This is highly advised in order to reduce the file size of the ebook. This is done easily by adding the audio file's URL to the applicable field.

The other option is to click the Add audio file button to add an MP3 file from your computer. 
In case you are integrating with an LMS, you can optionally assign this audio element to a defined objective. Objectives may be defined from the Book manager