▎ 摘　　要

NOVELTY - The apparatus (318) has first and second electrodes (319, 320) for applying voltage to reduced graphene oxide layers (322) to generate an electric field across a graphene oxide stack (321) in a sound output mode. The reduced graphene oxide layers are adapted to collect electrical charge induced in the reduced graphene oxide layers by vibration of a piezoelectric diaphragm (301) in response to a sound input wave in a sound input mode, where the collected electrical charge creates voltage between the first and second electrodes corresponding to the sound input wave. USE - Apparatus such as electronic device, portable electronic device, portable telecommunications device, mobile phone, personal digital assistant, tablet, phablet, desktop computer, laptop computer, server, smartphone, smartwatch, smart eyewear, wearable device, loudspeaker, microphone, ultrasonic device, sensor, range finder, identification tag, identification tag reader, imaging system, acoustic microscope, medical device, sonicator, transmitter and receiver (all claimed). ADVANTAGE - The apparatus can simply prevent dust particles from reaching components of a loudspeaker by a dust cap. The apparatus simplifies construction of piezoelectric speakers reduced cost and easy to manufacture. The apparatus achieves size reduction of loudspeakers and microphones without sacrificing audio performance. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following: (1) a method for using an apparatus (2) a method for making an apparatus (3) a computer program comprising a set of instructions for using an apparatus. DESCRIPTION OF DRAWING(S) - The drawing shows a cross sectional view of an apparatus. Piezoelectric diaphragm (301) Apparatus (318) Electrodes (319, 320) Graphene oxide stack (321) Reduced graphene oxide layers (322)