Detection and suppression of keyboard transient noise in audio streams with auxiliary keybed microphone

In this paper a problem in transient noise suppression for audio streams in laptop and netbook devices is addressed. One or more microphones record voice signals which are corrupted with ambient noise and also transient noise from keyboard and mouse clicks. In the current work, a synchronous reference microphone is embedded in the keyboard which allows for measurement of the key click noise, substantially unaffected by the voice signal and ambient noise. An algorithm is here presented for incorporation of the keybed microphone as a reference signal in a signal restoration process for the voice part. The problem is substantially complicated by the presence of nonlinear vibarations (we postulate) in the hinge and casework of the laptop, which renders a simple linear suppressor ineffective in some cases. Moreover, the transfer functions between key clicks and voice microphone depend strongly upon which key is being clicked. A very low-latency solution is proposed in which short-time transform data is processed sequentially in short frames and a robust statistical model is formulated and estimated using Bayesian inference procedures. Results with real recordings show a significant reduction of typing artefacts at the expense of small amounts of voice distortion.