On UK TV the majority, but by no means all adverts are subtitled (so long as you have them turned on in the first place). Online, I see very few subtitled. However I came across a campaign from Nike promoting the use of a twitter hashtag #MAKEITCOUNT that has subtitled it’s advert online for the deaf and hard of hearing. The difference is they have subtitled the graphics and not the audio (which is music lyrics) which is traditionally what subtitles are used for:
The subtitles have also been used in the more conventional way to translate into other languages, but again it is the graphics that are translated and not the music audio:
What I found interesting is that Nike have also chosen to match the graphics style of text on screen and replicate as best as they can with the subtitles too. Here is an illustration:
This includes adding the “@twitterhandle” names of the athletes appearing in the advert in the twitter handle style. This is included both in same language subtitles and the translation subtitles:
See for yourself by watching the subtitled Nike #MAKEITCOUNT advert here:
Do you like this? Or would you rather see the audio subtitled? I suppose it illustrates that for Nike the key messages they want the viewer to understand are in the graphics and not the audio in the first place. And if it is not, they really should be subtitling the music audio!