Wait but isn't this the purpose of the chirping sound when the crossing signal comes on? Far more effective and serves more than one person. However I realize it may not work on people who are both blind and deaf.
If there are two crossings next to each other where either can be on green while the other is red, the noise wont be there. It's to make sure that someone waiting at the red crossing does not hear the noise and cross. I think the article mentions that somewhere.
The intersection crossings in my hometown and in my current city all have noise. They just use different noises for the different directions. E.g., N-S crossings might chirp while E-W crossings might beep. (I don't remember exactly what the rule is, but I'm sure a blind person would.)
At my university, they'd make the chirping noise, but it'd also state which road has the walk sign. So it'd repeatedly say "Farm Lane Walk Sign" while the sign was on.
As per the article, those are not installed at every intersection. In my experience, they're rare outside of large cities.