Noise Cancellation Technology

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UmeVoice, Inc.Vikas RangarajanSr. Software
Engineer

• Noise Cancellation Technology
• for delivering clear audio

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Introduction

• Speech recognition in mission-critical
  application environments Wall Street trading
  floor BUY 10000 IBM at 93-1/4
• Problem of successful speech recognition in
  highly noisy environments
• Searched the world for best noise-cancelling
  solution
• Serendipitously led us to the development of our
  own noise-cancelling technology to effectively
  provide clear audio while eliminating 100dB of
  background noise
• Use of this technology to develop products for
  clear communication and accurate speech
  recognition.
• theBoom

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Why Audio Clarity is Crucial

• High signal-to-noise ratio amplitude of desired
  signal (speech) is much higher than the noise
• Flat frequency response the speech signal is
  passed through with minimal change to the
  frequency spectrum
• Face to face human communication is more tolerant
  to noise mixed with speech
• For long-distance human communication, audio
  clarity is more important
• Imperative for speech recognition

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Importance of clear audio for VoIP

• Increasing mobile usage of VoIP applications
• Noisy environments are typical (airports,
  conferences, cafes)
• A clear speech signal enables applications to use
  Variable Bit-Rate (VBR) and Average Bit-Rate
  (ABR) more effectively
• Elimination of background noise improves VAD
  (Voice Activity Detection)
• Improved bandwidth utilization by effective
  silence detection using techniques like
  Discontinuous Transmission (DTX)

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The passive approach and its benefits

• Prevention of noise from entering an audio signal
  without using a feedback mechanism
• Based on acoustic principles or physical
  properties of sound waves
• Real-time information about the noise or the
  desired sound signal is not used by the mechanism
  performing the noise-cancellation. This
  eliminates the need both for a processor and
  therefore a power supply.

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Electronic noise cancellation

• Digital Filters Signal enhancement using digital
  signal processing
• Active Noise Reduction Noise is reduced by
  generating a cancelling anti-noise signal which
  is equal to, but 180 degrees out of phase with
  the noise.
• Techniques are all frequency dependant, which
  impacts frequency response negatively since there
  is inherent overlap in frequencies between
  desired speech and undesired background noise.
  Sometimes speech signals are incorrectly
  recognized as noise and vice versa.
• Additional constraints Need processor and power
  supply

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Noise rejection
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Average Noise Rejection
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Summary

• Noise cancelling technology adaptable to
  different form factors of handsets and headsets
  (theBoom, theBoom Quiet)
• Noise cancellation technology being used in US
  Military, Dept. of Homeland Security and Car
  Racing (UmeCobra)
• Noise-Robust speech recognition applications used
  on trading floors
• Development of desktop and handheld applications
  with noise-robust speech recognition capabilities
  with the help of noise-cancellation technology

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Vision of the Future
The freedom to communicate wherever you are and
the ability to whisper and be heard. www.umevoice
.com