Help with rear noise

[Guest intrigueing]

Ok the car is a friends 95 leg wagon auto - 150K on the clock. 10K ago we did the rear brakes (they were noise free for some time) - pads and rotors new - non-OEM. He now gets some mild sweaking from both sides - that does not concern me.

The car when going 55+ intermittantly gets a very loud chirping from the left rear whose frequency is tied to speed. With the window down it is like a bird jumped inside your head. The noise is usually brought on by hitting a small bump, and the noise immediately goes away when the brakes are applied. When the brakes are released immediately the noise comes back. The e-brake has no impact on the noise. Any ideas? Brakes / wheel bearing / rear diff? Why would this be so intermittant?

[Guest ferret]

This is one place on my 90 Legacy LS I learned to use Subaru ONLY pads/anti-rattle backing plates. The replacement pads are 'squirming'. Thats why it goes away when applying the brake pedal, but not the emergency brake. The E brake uses the small brake shoes inside the rotor hub. Some may say I'm nuts for using the Subaru Pads, but since my 1st rear disk replacement and noise, the Subaru pads have at least been quiet.

P.S. Rear bearings make a loud ROLLING sound like a steel caster rolling across a concrete floor.

My $.02