Flexible, transparent single-layer graphene earphone

We demonstrate a novel flexible and transparent earphone based on single-layer graphene (SLG) for the first time. The SLG earphone operates in the frequency range of 20 Hz to 200 kHz and has a highest sound pressure level (SPL) of 70 dB with a 1 W input power. The SPL emitted from one to six layers of stacked SLG are compared. It is observed that the SPL decreases with an increasing number of stacked layers. The SLG earphone is packaged into a commercial earphone casing and can play music. Compared with a conventional earphone, the SLG earphone has a broader frequency response and a lower fluctuation. Testing results in both time- and frequency-domains show a frequency doubling effect, which indicates that the working principle is based on the electro-thermoacoustic (ETA) effect. As the SLG earphone operates in both the audible and ultrasonic frequency range, it can be used for a wide variety of applications, including for interspecies communication.