National Semiconductor Corp. has unwrapped the first in a line of audio products incorporating far-field noise suppression technology. This unique technology delivers more natural-sounding voice quality by eliminating the output frequency distortions and other audio artifacts common with digital signal processor (DSP) or microprocessor software-based systems that use sub-band frequency processing algorithms to implement noise suppression, according to National Semiconductor.

The PowerWise LMV1088 dual-input microphone array amplifier, which uses National’s far-field noise suppression technology, reduces background noise and improves voice communication clarity in mobile phones, two-way radios and powered headsets. Part of National’s PowerWise energy-efficient family, the device consumes one-tenth the power (1 mA) of comparable DSP or microprocessor software-based systems, setting a new standard for low power consumption, said the supplier.

The LMV1088 dramatically improves the talker’s voice-signal-to-background-noise ratio in the communications system while retaining natural speech quality. The improvement directly translates to clearer voice signals on the receiving end of the communications link and an increase in customer satisfaction. Additionally, the voice-signal-to-background-noise improvement allows increased accuracy by voice recognition systems since the background noise is not a significant part of the signal to discriminate against, stated National Semiconductor.

The LMV1088 is a dual-input microphone array amplifier offered in a miniature 3.5 mm by 3.5 mm, 36-bump micro SMD package. The amplifier draws only 1 mA of supply current. It has a power supply rejection ratio (PSRR) of 85 dB at 1 kHz, with a typical signal-to-noise ratio (SNR) of 60 dB and less than 1% total harmonic distortion plus noise (A-weighted THD+N). It is designed for use with two microphones in an end-fire array configuration. The microphones can be spaced in a line 1.5 cm to 2.5 cm apart from each other, or the equivalent acoustic path distance. The optimal distance for the person speaking into the handset or headset microphone is 2 cm to 10 cm.

The amplifier’s automatic calibration circuitry compensates for the microphones gain and frequency response variations, eliminating the need to use expensive matched microphone sets, while allowing flexible placement of the microphones in the final product. The calibration data is stored in the LMV1088’s internal EEPROM memory. The calibration sequence chooses the optimized coefficients for the two microphones’ spacing and acoustical environment. The LMV1088 features four I2C compatible, selectable operating modes: default noise reduction, microphone 1 pass through, microphone 2 pass through or microphone 1 & 2 sum.

Available now, the LMV1088 is priced at $9.95 each in 1,000-unit quantities.

• www.national.com/pf/LM/LMV1088.html

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