In typical voice communication systems voice signal levels may vary in a wide range due to varying distances between the user and the microphone and also due to properties of the communication channels.
Dynamic Range Compression (DRC) is the simplest way to equalize the signal levels. Compression reduces the dynamic range of a signal by lowering (compressing) strong speech segments while fully preserving weaker segments. As a result, the whole signal can be additionally amplified so that weak signals are better heard while strong signals do not overload the power amplifier, loudspeaker or user’s ears. It was discovered a long time ago that compression is a hidden weapon of commercial advertising, allowing increase in perceptual loudness while preserving all "objective" measured sound levels.
DRC is a standard part of Alango Voice Communication Package (VCP). It can be on both microphone and speaker channels with minimal required resources and no additional delay.
A well-known DRC problem is that it actually reduces the Signal to Noise ration by attenuating strong voice while preserving noises. Alango’s Voice Communication Package also offers an advanced solution by combining DRC with a fast and reliable Automatic Gain Control (AGC) algorithm. AGC technology digitally increases signal gain (amplification) when the voice signal is weak in contrast to compressing the voice signal when it is strong. Gain change does not occur when voice is not detected by the Voice Activity Detector (VAD) thus preventing amplification of ambient noises during speech pauses. In noisy places people tend to speak loudly which automatically sets the microphone channel gain to a small value thus reducing ambient noises while keeping the voice of interest at the optimal level. Alternatively, in a quiet environment people speak softly so their voices are amplified by the algorithm without too much noise.
In practice, a combination of AGC and DRC algorithms provides the best results.
Mobile phones, Bluetooth headsets, hands-free kits, video/audio conferencing equipment, voice recorders, intercom systems, voice controlled devices and many others.
Although it can be used standalone, Dynamic Range Compression and Automatic Gain Control technologies are also integrated with other Alango voice enhancement technologies into one Voice Communication Package (VCP). The package also includes acoustic echo cancellation, stationary and transient noise suppression, (optional) adaptive dual microphone, automatic volume and equalization control and several other technologies.