National Semiconductor has introduced the PowerWise LMV1088 dual-input microphone array amplifier, the first in a line of audio products using analogue far-field noise suppression technology. The device is said to reduce background noise and improve voice communication clarity in applications such as mobile phones, two-way radios and powered headsets, while at the same time consuming one-tenth the power of comparable DSP or microprocessor-based software systems.
According to the company, the far-field noise suppression technology delivers better voice quality by eliminating the output frequency distortions and other audio artefacts common with DSP or microprocessor software-based systems that use sub-band frequency processing algorithms to implement noise suppression.
Unlike DSPs and processors, the LMV1088's continuous-time analogue processing provides instantaneous response to voice and background noise signals and allows noise suppression to be integrated in phone handsets or powered headsets without any need to develop and test voice-processing software.
The LMV1088 is designed for use with two microphones in an end-fire array configuration. The microphones can be arranged inline 1.5 to 2.5 cm apart or with or the equivalent acoustic path distance. The optimal distance for the person speaking into the handset or headset microphone is 2 to 10 cm.
Automatic calibration circuitry compensates for the gain and frequency response variation of the microphone, eliminating the need for matched microphones and enabling flexible placement of the microphones in the final product. The calibration data is stored in internal EEPROM.
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