If you or your students do not like the feedback sounds in the player, you can turn them off using the icon in the top left corner of the player, which should look like one of these three icons:
The first means all sounds are on, the second turns off feedback sounds, the third turns off all sounds. Tap or click the icon to change between them; if you just want to turn feedback sounds off, change it to the second option.
The player does not support other feedback sounds at this time.