Audio description icon in Material Design style

[OwenEdwards]

Although the existing audio description icon is the standard one (and the one I suggested!), it's in the same style as the more conventional CC button. There isn't a suitable audio description icon in the Material Design library, but I'm sure someone could make one. The obvious thing would be to just do the letters 'AD' like the 'CC' icon, but it would be very close to the 'HD' icon.

So I'm opening this issue for suggestions/ideas?