Using ToDo in a Safari web browser can produce a continuous, loud, white noise (high pitched buzzing) sound which can be unpleasant, and almost painful with headphones.

Software versions: MacOS 10.12.6; Safari 10.1.2 (12603.3.8)

To reproduce:

Microsoft ToDo is open and logged in. It is then moved to a pinned Safari tab and is not the active tab in the browser.

Change audio inputs on the Mac, (i.e. by connecting to a bluetooth audio device, or by docking and undocking the Mac from a Monitor with integrated speakers).

This will then often result in the loud white noise sound.

The sound will stop when the ToDo browser tab is made active and then closed.

Additional Notes:

I don't believe that ToDo is supposed to be playing a sound at the time the noise triggers. For example - I don't believe that a reminder alarm or task completion sound should be attempting to play at the time the noise starts. There seems to be no correlation between these genuine sound events and the start of the noise.

It isn't reproducible 100% of the time (for example I can't force the issue to occur now as I'm writing this, but it is significantly unpleasant, and happens often enough (estimated once every 3 or 4 times I dock/undock or connect to bluetooth audio throughout my normal workday) that I consider this a major bug.

I can't rule out this potentially being a bug with Safari, but it has not occurred with any other web site. On every occasion the white noise starts, ToDo has been open in a browser tab (although not the active tab) and the noise has ceased when the ToDo browser tab is closed.

It doesn't appear to be a problem with my hardware. It has occurred on a MacBook Pro on its inbuilt speakers, and on a seperate iMac with bluetooth audio device.

Please feel free to contact me if I can assist with testing any particular scenarios to narrow down the reproduction of the issue.