To turn off Growl Notifications altogether, navigate to Account Settings under your profile icon in the bottom left corner. Disabling Growls will turn off the sounds that go with it.

As an additional workaround that does not require disabling any settings, you can use the Chrome browser, right-click on any open Helpshift tabs, and select ‘Mute tab.’

To learn more about Growl Notifications, see What are Growl Notifications, and when do they appear?