On Android devices, you have the option to disable the sounds that accompany alert notifications or disable alert notifications completely. 

Open the CleverLoop app, and go to Base Station setting page (by clicking the screwdriver and spanner icon in the top right corner of the screen).

You can now choose to enable 'Push Notifications' or 'Notification Sound'. Toggle the slider for each of these to the on / off setting that you want and you are done!