When I press my brakes on my "Toyota EchO' there is an unsual sound coming from the wheels?

have the front end steering joints and suspension checked by an accredited front end specialist. Check the wheel bearings and cv joints for serviceability. Although you say it is only occasionally it is a critical issue as on any occasion it may place you or others in harms way.

CV shaft

You have to remove your wheel, suspension arm and track rod from the hub then remove wheel hub. You then remove the bearing from it and fit a new one, sounds easy? It isn't. Unless you have the correct tools and equipment I advise you get a mechanic to fix this one or you could mess up the new bearing.
Tools needed: Various spanners and sockets, hammers, ball joint splitter, hydraulic press and various drifts, Puller and maybe a grinder.

you have to remove brake pads, rotors, struts, tie rod end and lower ball joint. whole unit comes out then. the bearing has to be pressed out and new one pressed back in good luck

Thats the wheel cylinder. When you press down on the brake pedal it is forced out spreading the shoes to push againt your drum and stop the vehicle

Slowly apply the park brake while driving in a safe area. If the noise is present the rears are the area of concern as these are the only brakes applied. If the only time the noise is present the brake pedal is depressed, the front brakes need attention.

worn brake shoes or discs easy and cheap fix just bring to garage will fix no problem

take off the tire remove the brake drum let go the four bolts on the inside part behind backing plate should be able to tap the whole unit out without taking off the brake pads

get it inspected, You may just have one sticking caliper that need replacement. the brake pads will be pretty worn on that wheel so you may needs pads also.

Apparently most dealers will tell you that this sound is from rust building up on the brake rotors because you missed your regular maintenance.