Some firms have a policy of making sure that everyone with an officially recognised disability gets an interview.
I won't go as far as to say it will never be an issue, and there will be some jobs won't be ideal for you. But I'd also say that it doesn't really matter since most employers are worse than most banks about this sort of thing, so if you were comparing it with other types of employment, to me it would be a no brainer.
However, there's a lots of legal crap out there, that although for "your benefit" I think makes your job hunting harder. Both personal discomfort and fear of you suing them will make employers reluctant to ask questions like "can you use a phone ?"
So being the sort of person I am, I'll ask it for them.
Can you use a phone ?
What tech can you use to make a phone usable ?
Do you need to be in lipreading range / line of sight when talking ?
Does your existing hearing aid have the ability to interconnect with the banks voice tech ?
VOIP. Bluetooth, etc.
How well does your hearing aid cope with environments that are both acoustically and electronically noisy ?
Can you use a cell phone ?
Are you undergoing any medical treatment for it ?
How well do you speak ?
What other disabilities do you have ?
There's other stuff, but I'm guessing you've lived your life enough to think them up yourself.
The reason you need to answer these questions is to take the initiative in the interview process. If you can truthfully say "my earpiece can work in a screaming football crowd", and work through how it's not going to be a big issue for them, you will help a lot.
Be clear here how it works. After interview the managers will get together and perhaps ask "can he work with traders, with the ear thing ?", and what you don't want is for that question to go unanswered when you aren't there to answer it.
Or they may not explicitly say anything, but form their own conclusions, again not good.
A second and perhaps more important issue is initiative.
Bankers want people who push hard, think ahead, and who can deal with shit when it happens.
So by demonstrating that you've thought through all the hassles your hearing gives you, and found solutions to them, they will rate your character more highly, which is a real win.
..and some will just pretend to interview because HR made them, we can't fix that, but we can make a good case to the others who I believe to be the majority.
There is a lot of tech out there that can work for you, and compared to your cost of employment it's pathetically cheap. Find the right person in IT, and they will see getting you kitted out as a personal challenge.
One of the (few) joys of being a senior partner at a headhunting firm is that I get to decide what our policies are, and we've always tried to give an extra push to those who need to push harder, so if you have specific questions you don't want to talk about on a public forum,
I'm Dominic # PaulDominic.com