Most loudspeakers work using a diaphragm that creates pressure waves in air by mechanically vibrating. “For human audibility, an ideal speaker or earphone should generate a constant sound pressure level from 20 Hz to 20 kHz, i.e. it should have a flat frequency response,” say Qin Zhou and Alex Zettl who are both at the University of California, Berkeley.
Today, these guys unveil an earphone-sized speaker that more or less matches this requirement. What’s unusual about this speaker is that the diaphragm is made from a few layers of graphene, the carbon chicken-wire material that is revolutionizing everything from transistor design to particle physics experiments.