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Only SmartAVC™ offers all of these advanced features:

  • Controls volume without sacrificing clarity
  • ‘Knows’ which noises interfere with speech intelligibility – and which don’t
  • Adjusts volume when needed, and only when needed, to maintain intelligibility
  • Smoothes volume fluctuations
  • Eliminates static-like bursts caused by noise spikes


SmartAVC™ compensates only for noise that interferes with speech, not total noise. Every 25 milliseconds, about the blink of an eye, SmartAVC™ measures the noise spectrum and calculates a preferred speech-interference noise level (PSIL), which is a direct measure of how much the ambient noise interferes with intelligibility of speech. Then, based on the changing PSIL, SmartAVC™ determines whether the speech-interference component of the noise is a transient spike that can be ignored, or a persistent noise requiring volume adjustment.

SmartAVC™ analyzes noise in both the frequency domain and the time domain. Nearly all the information content of speech is carried in the frequency band from 200 Hz to 6 kHz. SmartAVC™ ignores the high-frequency and low-frequency content of noise that does not interfere with intelligibility, and weights the speech-interference noise by frequency in accordance with how much it degrades intelligibility. Even noise at a frequency that interferes with speech may not degrade intelligibility, however, if it is brief. Intelligibility of full sentences is virtually unchanged by noise impulses less than about a quarter to a half second, no matter how loud they may be, because such short impulses mask no more than one or two syllables. SmartAVC™ smoothly adjusts to rapid noise changes and ignores transient noise spikes.


Devices that transmit, such as mobile phones or Bluetooth-enabled headsets, are already equipped with microphones. The existing microphones can be used to characterize the noise environment for SmartAVC™, so that no hardware changes to the system are needed. In such systems, SmartAVC™ can be implemented by changes at the chipset level or to the DSP alone, and at negligible delta cost. This implementation of SmartAVC™ requires no changes at all to handset or headset hardware.


SmartAVC™ can provide a premium quality of service in systems equipped with a secondary microphone. The secondary microphone can be used to characterize the noise environment accurately for the highest quality volume control. The microphone best suited to this purpose is omnidirectional and high gain, like the secondary microphones with which many phones are equipped today. This implementation of SmartAVC™, with a microphone dedicated to high-fidelity characterization of noise, provides premium quality of service with no changes at all to hardware, and at negligible delta cost.

The Experience

An A-B demonstration unit (shown on this page) is available to compare the performance of SmartAVC™ to conventional AVC. The observer can produce his own noises and hear in real time how SmartAVC™ and conventional AVC each adjust the volume of a pre-recorded speech in response. The response of the conventional AVC quickly becomes annoying. The smooth and graceful response of SmartAVC™ feels like an auditory luxury. Contact us for a demonstration of the SmartAVC™ experience. To download an interactive app allowing you to hear the advantages of SmartAVC™ for yourself, click on the “Audio Demonstration” tab above.

Technical References

SmartAVC™ Executive Summary
SmartAVC™ paper published in Proc. 34th IEEE Sarnoff Symposium, May 2011
SmartAVC™ presentation to IEEE Communications and Signal Processing Societies


For a short video interview on SmartAVC™, filmed at the Tech Coast Angels Quick Pitch event in San Diego in October 2010, click on:

SmartAVCTM Video

A-B breadboard demonstrates SmartAVC™ performance superior to conventional AVC