Hello K.B,
I am sorry to hear your having problems with the sound you can file a service request here
https://khanacademy.zendesk.com/hc/en-us/requests/new?ticket_form_id=260948

Also the following article will explain on the information we need personally in bug reports
https://khanacademy.zendesk.com/hc/en-us/articles/202834460-What-information-do-I-include-to-submit-an-effective-bug-report-

From my own personal experiences I can say the Khan Academy Support Team is quite helpful so directly filing a service request will be the best option.

Please though know should you have any further questions in future please don't hesitate to ask I will be happy to help!

I,too, don't have sound with the ipad app