Would we really consider that "standard" gear? It's not like he uses it enough for it to count for that. Also as good as DD's senses are, there's no possibility they're good enough where he could even hear it.
It may just be he can hear pretty much anything in a human range, but stuff like a bat signal or dog whistle is beyond him. There's a good chance it's not, but it was never pointed out so it's something to consider.