Investigation on the noise emission mechanism of PC keyboards

The noise emitted from information technology (IT) machines is one of the main annoying sound sources in office environments. Although recent research has aimed at reducing the noise emitted by personal computers (PCs) no major effort has been invested with the study of the characteristic and reduction of the noise emitted by PC keyboards. This paper studies the noise emitted by PC keyboards in order to give indications and provide strategies in order to reduce such noise. The main objectives of the research are: 1) suggesting an experimental repeatable way to measure the noise emitted from a keyboard; 2) characterising keyboard noise; 3) identifying possible sources of noise in order to understand the ways of possible intervention. A test rig has been built in order to generate repeatable tapping of the keys which resembles human tapping. Force, acceleration of the key and noise have been recorded and analysed. Noise emitted by different keys and different keyboards have been also compared. The designed test rig has proved to be a reliable tool to measure and study the noise emitted by IT keyboards. The spectral investigation showed that the maximum noise contribution is due to the impact of the key with the base of the keyboard, and to the free oscillation when the key is released. It is also shown that the keyboard structure contributes to the noise radiation.