Voice Interface Market

Voice is becoming the killer application. Whether it is in the PC, in the Smartphone, or in your car, voice related functions will become a part of everyday life, and in turn fuel the growth in these consumer markets. Thanks to wireless technology such as Bluetooth, connecting a mobile phone to a car’s hands-free kit is now seamless. The advent of VoIP and various IM programs provides a low-cost alternative to enable communication via the internet. For these applications, capturing a clear and noise-free signal is vital to providing a high-quality user experience. As such, the voice interface becomes critical.

Array Microphone

Under less than ideal conditions, even the best microphone, whether embedded in a car’s visor or in a laptop, does a poor job of capturing sound. An array microphone can do a better job of isolating a sound source and suppressing ambient noise and reverberation. Leveraging the information gathered by the multiple microphones about the voice and surrounding environment, an array microphone can process the signals in such a way that effectively forms a beam to pick up the wanted signal within the beam, and cancel out noise outside the beam.

However, the broadside array microphone is still impractical and limited in two ways:

• Requires at least 30mm between each microphone, putting placement and space constraints on the end solution.
• Can only cancel noise on a horizontal plane. This makes it difficult to accurately isolate the sound source, while allowing noise to leak into the beam. Noise can leak in from above and below the pie-shaped beam.

Small Array Microphone

A new array microphone technology, small array microphone (SAM), is the big leap in voice interface technology. Requiring only 5mm between microphones, SAM can be deployed in practically any situation or application. SAM uses a fundamentally different algorithm than the traditional array microphone to process the voice, effectively forming a 3-D cone shaped beam. As such, any noise outside the beam, whether above or below, will be cancelled out, without any leakage.

SAM technology leverages the strength of both small array adaptive beamforming, noise cancellation and none-linear frequency-domain filtering technologies, as illustrated in Figure 2. The front-end beamforming create two beams: the main beam focuses on the voice, and the reference beam senses the noise only. The reference signal is first used to adaptively cancel the linearly correlated noise in the main beam. The noise post-filter further suppresses the remaining noise. In this way, SAM can achieve higher noise suppression.

SAM Key Features

• Small array size. This makes it especially suitable for mobile communication applications.
• Narrow beam width, and therefore is capable to achieve high SNR enhancement.
• Strong echo rejection when the speaker is placed at the different direction of the voice. This makes it possible to achieve much high echo cancellation performance.
• Suppressing both stationary ambient noise such as car engine and road noise, and non-stationary noise such as radio or other people voices.
• Flexible configuration with one or multiple microphones for different applications.
• Good voice quality and small processing delay, making it suitable for wireless phone and speech recognition application.

For more information on how SAM compares to broadside array microphones, and how users will benefit in specific applications, please visit the pages below:

1. SAM vs. Broadside Array Microphone
2. SAM in Automotive Hands-free Applications
3. SAM in PC/VoIP Applications
4. SAM in Handheld Applications