Graphene in loudspeakers and earphones

Loudspeakers and earphones are used with portable devices such as smart phones, laptops, notebooks and tablets. Inside a speaker a flexible material such as paper or plastic forming a thin diaphragm vibrates and amplifies these vibrations, pumping sound waves into the surrounding air and towards the ears producing different sounds depending on their frequency.
Sound device
The quality of a loudspeaker depends on how flat its frequency response is – that is, on the ability of the design to deliver a constant sound pressure level from 20 Hz to 20 kHz in the audible range. Presently they employ conventional type of speakers which have limitations in their operation in respect of size, frequency response and power consumption.
Graphene loudspeaker
Researchers at the University of California at Berkeley have made a graphene loudspeaker that, while of no specific design, is already as good as, or even better than, certain commercial speakers and earphones.
graphene loudspeaker have ultralow mass, has a fairly flat frequency response in the human audible region and very strong so that it can be used to make very large, extremely thin film membranes that efficiently generate sound. This also means that the speaker does not need to be artificially damped (unlike commercial devices) to prevent unwanted frequency responses, but is simply damped by surrounding air. Such device can operate at just a few nano-amps and so uses much less power than conventional speakers.
Working
The researchers claim that they made loudspeaker from a 30 nm thick, 7 mm wide sheet of graphene grown by chemical vapour deposition process. The diaphragm is sandwiched between two actuating perforated silicon electrodes coated with silicon dioxide to prevent the graphene from accidentally shorting to the electrodes at very large drive amplitudes. When power is applied to the electrodes, an electrostatic force is created that makes the graphene sheet vibrate, creating sound. By changing the level of power applied, different sounds can be produced. These sounds can easily be heard by the human ear and also have high fidelity.
The Berkeley researchers claim that the technique adopted for fabricating the speaker is very straightforward and could easily be scaled up to produce even larger area diaphragms and thus bigger speakers.

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