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OKI Develops Compact Sound Source Separation (SSS) Microphone Module with Ambient Voice Suppressor (AVS) Technology

For clear communication in noisy environments

AVS embedded compact
sound source separation
microphone module

TOKYO, January 29, 2013 -- OKI (TOKYO:6703) has developed an ambient voice suppressor (AVS) technology that accurately extracts voice periods and suppresses noise, and a compact sound source separation (SSS) microphone module based on this technology. Achieving significant improvements in separating and extracting the speaker's voice from surrounding noise, the AVS technology makes possible stress-free communications via smartphones and other mobile devices in noisy environments, such as exhibition halls, inside vehicles, train stations, and so on.

Smartphones have grown increasingly popular in recent years and are often used in hands-free for teleconferencing or other purposes, as well as for ordinary phone calls. When a mobile phone is used for hands-free calls in noisy public locations, the phone's microphone might pick up surrounding voices and background noise, generating howling or degrading speech communication quality.

"To counter these problems, OKI has developed AVS technology based on many years of research on sound source separation.(*1)" says Takeshi Kamijoh, General Manager of Research and Development Center at OKI. "AVS technology uses multiple microphones to suppress surrounding voices and background noise. In the verification test using a newly-developed compact SSS microphone module in which AVS is embedded, we confirmed that the technology provides improved clarity in noisy environments (bus terminals and train platforms)."

OKI plans to promote the use of compact SSS microphone modules and sound source separation software featuring the AVS technology in information communication devices and continue to develop for further applications.

Some developments related to AVS were based on the joint development with Professor Tetsunori Kobayashi, Waseda University.

Overview of the AVS (Ambient Voice Suppressor) technology

AVS is OKI's proprietary technology that distinguishes a speaker's voice from surrounding voices and suppresses only the surrounding voices. AVS detects the direction from which input sounds arrive, suppressing signals coming from directions other than the front (e.g., the voice of someone next to the speaker and background noise).

Figure1: Overview of AVS technology

The AVS detects the sound arrival directions based on cross-correlation(*2) of directional signals generated by filtering along four axes. Cross-correlations are greater for input signals arriving from the front and lower in other cases. Therefor, when the cross-correlation is small, the AVS identifies the sound as unrelated to the speaker's voice and suppresses it. In this way, the AVS extracts vocal components arriving from the front.

The AVS function can accurately distinguish the speaker's voice from the voice of someone next to the speaker and extract the speaker's voice. We confirmed high detection accuracy of the target voice period in the performance test at a bus terminal (noise level: 60 to 70 dBA) and on a train platform (noise level: 60 to 85 dBA).

A compact SSS microphone module with AVS also provides a function that automatically corrects for differences in sensitivity among four microphones in the module, based on the AVS function that identifies the direction of signal arrival. This function prevents differences in microphone sensitivity from degrading audio quality, which result in more natural voice quality. In addition, the function ensures consistent sound quality and extraction performance, even if microphone characteristics change over time.

Features of the compact SSS microphone module incorporating AVS

  1. Improved voice call quality

    The technology improves the clarity of the speaker's voice by suppressing background noise and surrounding voices in noisy environments. Sound diffraction occurred by hands-free conversations under extremely noisy conditions often generates howling. The AVS suppresses diffracted sound components, which eliminate howling and ensure clear voice communication.

    The AVS technology can improve not only mobile devices like smartphones, but also various other products with voice communication functions such as intercoms and videoconferencing systems, etc. The compact SSS microphone module is also suitable for ATMs, ticket-vending machines, and other technology incorporating voice communication functions.

  2. Preventing speech recognition system(*3) from false recognition

    Many of today's smartphones and car-mounted navigation systems have voice search functions with speech recognition technologies. In noisy locations, these functions might erroneously respond to not the user-speaker's voice but others. Under these conditions, the compact SSS microphone module suppresses surrounding voices and prevents the speech recognition system from false recognition.

Figure2: Directional pattern


  • *1 :Sound source separation

    A technology that extracts just the target sound source from a mixed sound including multiple-source sounds and various background noises.

  • *2 :Cross-correlations

    Feature value to show similarity of multiple signals.

  • *3 :Speech recognition system (technology)

    A system/technology that analyzes human voice signals and converts spoken words into text

About OKI Electric Industry (OKI)

Founded in 1881, OKI Electric Industry is Japan's leading telecommunications manufacturer. Headquartered in Tokyo, Japan, OKI provides top-quality products, technologies, and solutions to customers through its info-telecom systems and printer operations. Its various business divisions function synergistically to bring to market exciting new products and technologies that meet a wide range of customer needs in various sectors. Visit OKI's global website at http://www.oki.com/.

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  • * Information in the press releases is current on the date of the press announcement, but is subject to change without prior notice.

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