the more i browse this site...the more sh*t i come across from people who are just talking bullshit and obviously dont know about cars.....you guys provide opinions as if you are the best expert out there.....
who ever thinks that NEVER EVER spray anything on your discs obviously dont know what they are talking about....
i will still try to help as i have done my brake service many times...
the sound you hear is due to a rough contact b/w your pad and your rotor or brake disc. it can be due to several reasons...dust or worn out pads or rust deposits on either on any moving brake components.
im sure you can get a brake cleaner...just spray it all over the brake assembly....the disc, caliper and around...let it drip all the gunk and dirt.....once that is done....open the caliper bolt (its on the other side of the caliper)...swing open the pad holder up and take the pad out...check its condition for wear.
If you dont feel comfortable doing this urself...take it to a professional and tell the guy to clean the whole assembly and deglaze the pads.....
For all who said...NEVER EVER....do this....here is what i am talking about.