So it seems the best way is to handle it as if its a normal character with a bit of RP flavor. Of course, if they are looking for someone who is say wearing a red cloak they would be of no help there.
As far as combat, I'd leave it alone. You have adapted to your blindness so well as to pick up on the sound of bolts or arrows cutting through the air in your direction. You can use ambient sound to pick up on the location of those around you and you are paying such close attention that you keep track of not only your own location but that of your allies as well, leading you to not accidentally target them.
The big issue I see is if they get deafness cast on them. Immediately cause them to become totally disoriented not knowing who is an ally or an enemy. Roll percentile dice and develop a table for whether they target what they think they are targeting or not, dropping the odds for every round that goes by.
I myself am blind and you would be surprised how easy it is to navigate by sound. Sit down some time, next to a speaker, listen to a continuous tone, then place a piece of cardboard between you and the speaker. Or have a person step between you and it, notice the difference. That difference, with time and experience can tell you a lot, distance, shape, density, whether its porous, like a bush or solid as a wall, It's direction of travel etc. At this point in my life I don't need a speaker to be playing a constant sound to discern what is around me. You find over time silence itself is a sort of sound. That said If I were deaf I would have no clue what is going on.
Btw, the actual sensation of echo location is oddly more of a tactile one rather than an auditory one. It feels like an odd sensation running from the side of your forehead near the hairline above your eyebrow to the collar bone. Maybe make a rule like: Your acute senses have been honed by your training to give you a sense of your surroundings, you can discern shapes, distance, direction, and size of objects within 60 feet and approximate weight of moving objects you can hear at any distance. You must be able to hear them to discern weight. While a totally still or silent object still changes the background sound of the environment itself giving you an idea of size, shape, distance and direction.
So for the effect of deafness I'd completely eliminate all of the above aside from anything that might reverberate through the ground even a vibration in the air. Silence really should eliminate ALL vibration, if you argue it does not, then they should still be able to navigate while under the influence of silence. I'd argue it does eliminate all vibration in its area of effect, actually making it actually worse for a blind PC to be under the effect of.