In Sketchup for iPad you can watch small videos to see how to use each tool. When you do that, and the subsequently minimise sketchup the audio of that video starts playing, and repeating itself ad infinitum. The only way out appears to kill the sketchup app.
I see that the issue has been worked on. I don’t know when a fix will appear in an app update.
One thing to notice, if you return to SketchUp and start the same video going again, closing the video and leaving SketchUp in the foreground seems to stop the sound from repeating.