I just saw your post and I will take a try at answering your question.
I am assuming you are hearing the hydraulics coming alive. Unlike the 757, the 767 's hydraulic systems are arranged differently. The right and left systems are driven by an engine driven pump and an electric pump that is a demand pump. In otherwords, the engine driven pump, which is high volume and high pressure, runs continuously with the engine. However, when a high load system is used then the electric demand pump starts up to assist and backup the engine pump. The brakes are on the right system so perhaps that is what you are hearing.
Same can be said with the center hydraulic system. The flaps are on the center system which, when activated, brings the center Air Driven Pump on line. That causes a lot of noise as well. Now for the spoilers, each panel is powered by one of the hydraulic systems. So, they are causing all demand pumps to activate as well.
Hope this helped.