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DRC - Dynamic Range Compression

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About Dynamic Range Compression

Mobile voice communication is often conducted in noisy environments. The simplest way to improve speech intelligibility in a noisy environment is to increase the sound volume. Unfortunately, in many practical situations, the output sound level produced by a communication device is limited due to the amplifier, loudspeaker or power consumptions reasons.

The question arises: Can we modify the sound being reproduced by the speaker so that it becomes more understandable in noise, while preserving its level?
The answer is: Yes

The simplest way of doing that is to compress the signal. Compression reduces the dynamic range of a signal by lowering (compressing) amplitudes of strong speech segments while preserving amplitudes of weaker segments. As a result, weak signals are better heard in noisy situations while strong signals do not overload the power amplifier, loudspeaker or user’s ears. In a paper (link to scientific paper below) published in the Journal of Audio Engineering Society was shown that compression is a hidden weapon of commercial advertising, allowing increase in perceptual loudness while preserving all "objective" measured sound levels.

Dynamic Range Compression (DRC) is a standard part of Alango Voice Communication Package (VCP). It is performed on the microphone channel in the basic VCP version and on both microphone and speaker channels in the advanced VCP version.

Compression technology improves, but does not guarantee speech understanding. If the noise level becomes too large, it will mask even the enhanced speech. Automatic Volume and Equalization control (AVQ) technology progressively monitors the ambient noise spectrum equalizing and amplifying the reproduced sound accordingly. This guarantees that all important speech parts are above the noise level and the whole speech remains understandable, but never too loud in varying noise conditions. AVQ technology requires a reference microphone to monitor for noise monitoring. In voice communication terminal (hands-free kits, mobile phones, Bluetooth headsets) such microphone is already present, so that no additional hardware is required. AVQ is a part of the advanced VCP.

DRC and other technologies

Although it can be used standalone, Dynamic Range Compression technology is also integrated with other Alango technologies into one Voice Communication Package (VCP). The package also includes acoustic echo cancellation, stationary and transient noise suppression, speech enhancement, (optional) adaptive dual microphone, automatic volume and equalization comtrol, and several others.

Additional information

More detailed technical information and examples are available upon request.



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