I've just finished working on a film where one of the actresses is deaf ( she's also a dancer), my one brother also suffers significant hearing loss and much to most people's surprise a lot of deaf people do not 'hear nothing'- it's not silence, they often can hear quite a bit of significant sound or noise. They can also always feel vibration hence my friend's ability to dance professionally and some can hear some music. I do think the mother in this case was being contentious for the sake of it, and on that basis I do hope common sense prevails as I think the promoters tried their best, however as a matter of course it would be nice if all major gigs did supply an interpreter and that his interpretation was beamed onto at least monitors in one area where deaf people could choose to buy tickets. that would make the whole gig accessible to people with sensory impairment and improve a lot of people's experiences.