Scratch input
In computing, scratch input is an acoustic-based method of Human-Computer Interaction that takes advantage of the characteristic sound produced when a fingernail or other object is dragged over a surface, such as a table or wall. The technique is not limited to fingers; a stick or writing implement can also be used. The sound is often inaudible to the naked ear. However, specialized microphones can digitize the sounds for interactive purposes. Scratch input was invented by Mann et al. in 2007, though the term was first used by Chris Harrison et al.
History
A natural interface for musical expression operating on scratch input principles was first published and presented in June 2007. Later that year, it was extended to an implementation on a smartphone and also a wearable computer system.In 2008, the Scratch Input project demonstrated a mobile device input system utilizing scratch input, simultaneously popularizing the term. This system captured audio transmitted through a surface on which a mobile phone was placed, enabling the entire surface to be used as an input device.