[JackG]

If you push the clutch in (or put it in neutral) and coast, then hit the brakes, does it still make the sound? Or does it just make the sound when you accelerate and slow down using the engine, in gear?

Accell/decell torque on the engine with a bad motor mount could make some noise. If the clutch in/neutral test stops the noise, it would seem to be motor/driveline related.

If it still happens with the clutch in while hitting the brakes, you're likely looking at something in the suspension.

Hope that helps.