Is this noise normal while braking?

Not so easy for me to listen to the imgur link, but is it a single run of a few seconds usually when you apply or release the brake, or is it cycling like that over and over while you sit there stopped with your foot held on the pedal?

 

Not necessarily a concern. I usually describe mine as running every 'few' uses of the brake, but how many is a 'few' can depend on a lot of things (how hard the brakes are applied, pad clearance or rotor runout in the front, adjustment of the rears, etc.), plus it is not super loud and I'm sure there are times it runs that I don't notice it ... maybe most of them.

... which means the more attention you pay to it, the more it can seem to run, which can be a kind of obsessive spiral.

You can find threads where it has developed an obvious problem, and will sit there continually cycling without additional use of the brakes. If it gets there, or you get warning lights and the beeeep, you'll know it's a problem then.

 

By the way, do you routinely use the parking brake when you park?

The way the rear brake adjusters work, there have to be applications of the parking brake, mixed in with applications of the regular brake. If that doesn't happen often enough, the rear brake shoe clearance will increase ... which uses more brake fluid every time you apply them ... which runs the pump more often.