▎ 摘　　要

NOVELTY - The audio speaker has an electrically conductive membrane, such as graphene membrane (801), a substrate, a cavity (804), an electrically conductive trace, and a time varying voltage between electrically conductive membrane and electrically conductive trace. The time varying voltage moves the electrically conductive membrane in first direction to cause air to be moved from the substrate at first average velocity, and in second direction to cause air to be moved toward the substrate at second average velocity that is less than the first average velocity. USE - Audio speaker for use in liquid ultrasonic application, such as medical imaging. ADVANTAGE - The use of graphene membrane provides the ability to make very low and very high pitch sounds with the same and very compact speaker, provides the ability to make high volume sounds with a very small/light speaker chip, and provides a little graphene speaker that will cool itself with high velocity airflow. A graphene-drum pump system makes a speaker efficient, compact, and can produce sound over the full range of audio frequencies without a loss of sound quality. The audio speaker can draw/push air in/out the same vents, allowing everything to be on one side of the chip/wafer if desired, and the system does not require valves to work, which results in much lower complexity and cost. Contacting and wear of components are reduced and/or eliminated. There is no need to mount the device in a bulky enclosure, since the audio speaker sends audio waves out from one face of a chip. Reaction forces and unwanted vibration are canceled, if speaker assemblies are mounted on both sides of a chip. DETAILED DESCRIPTION - The cavity is bounded in part by the substrate, and has a volume that changes due to the movement of the electrically conductive membrane. The electrically conductive trace is located near the electrically conductive membrane. The electrically conductive trace comprises metal or silicon. INDEPENDENT CLAIMS are also included for: (1) a method to make layered device having enclosed void space; and (2) a method for producing audio signal from audio speaker. DESCRIPTION OF DRAWING(S) - The drawing shows a schematic diagram illustrating a graphene membrane transducer when the graphene membrane is being pulled toward the conductive trace due to electrostatic forces. Graphene membrane (801) Cavity (804) Vent hole (1201) Fluid flow (1302) Waves (1303)