Voice Quality Enhancement (VQE) software is a necessary component in the design of Large Room Conference Speakerphones.  One core piece to VQE in this application is multi-mic signal processing, such as acoustic beamforming.  The local users of the speakerphone are located in the far-field, ranging from 1 to several meters away from the device.  This distance decreases the signal to noise ratio and direct path to reverberation ratio of the desired signal.  Microphone array acoustic beamforming spatially filters sound in the direction of the active talker, reducing the perceived distance the user is from the device.

There are several ways to construct a beamforming algorithm, but the most common for this type of application is to pre-design a set of beamformer filters.  These beams provide the required angular coverage of the device.  Then a beam selection algorithm determines the beams that have active speech content and includes them in the output stream.

Another core piece of the VQE software is Acoustic Echo Cancellation (AEC).  AEC is required to remove the acoustic coupling between the loudspeaker and microphones.  The echo tail length can range from 128ms to 512ms depending on the design of the room.  The size of the room increases the required tail length over typical office spaces.  Glass walls and windows also significantly increase the RT60 time.

Since there is a wide range of distances from which the device can be used, the audio levels of the talkers will also have a wide dynamic range.  Automatic Gain Control (AGC) should be applied to the transmit signal path to normalize the audio signal to a target SPL.

voice quality enhancement conference speakerphone block diagram

The combination of these individual components into a Voice Quality Enhancement package creates a solution that provides superior audio quality for Conference Speakerphones.  Please contact us to learn more.