http://matthewdavis.co/spellingtest/ Audio appears in the inspect element but does not play. Approximately 1/3rd of the audio is affected. Working on Firefox, Chrome, and Edge.
Can you please add some more information about the system you're using to reproduce this bug? What version of Safari + WebKit (found in the Safari -> About Safari) menu. What version of the OS are you running? Etc.
mac safari 10.1.1, safari for iOS 10.3.2
seems like it's all working on safari technology preview 33 for mac