Smart Microphone for howling prevention: A context-aware audio device

Advancements in sensing and embedded computation are enabling the development of new context-oriented product designs. Computational devices that are aware of their context can respond appropriately given less direct user input, helping users focus on what they are doing rather than how they are doing it. Following a brief introduction, we review some prior context-aware devices with applications in audio. Then, we introduce the Smart Microphone, which reduces its gain if it detects that it is placed too closely to a loudspeaker in an acoustic feedback loop. The gain reduction stabilizes the feedback loop, preventing unpleasant acoustic howling and squealing sounds from occurring. The Smart Microphone employs an ultrasonic sensing technique to estimate the distance between the microphone and the loudspeaker. The microphone and loudspeaker transducers themselves can be inaudibly employed in the ultrasonic band to perform the sensing, without interrupting any audible program material. Measurements performed in a real room validate the ultrasonic sensing technique.