The 2 most common rear "suspension" noises are unlubricated sway bar bushings and the emergency brake cable. There are rubber bushings around the brake cable with fins on them. Put lubrication between these bushings and the bottom of the car and see if it makes a difference. You can also get under the car and just yank on the cable to see if it makes a noise (it flexes a good bit when you are driving). Other than that,I don't know what to tell you. I'm getting an awful noise just like the one you are describing and I just replaced my suspension. I'm going to try to fix it when I get back home where I have a garage, but so far I've had no luck
