Radio communications are still a prevalent component in military, public safety and industrial operations. Fast, reliable and secure communications are paramount. In these operations, the acoustic environment in which they are used is often very noisy. The microphone on a radio not only captures audio of the radio operator, but in addition, loud industrial equipment, vehicle noise, helicopter noise, artillery and crowd noise. Voice Quality Enhancement (VQE) software is a critical component to a radio design to ensure the message of the radio operator is understood correctly.
To properly address the noise, the VQE software package should include dual mic noise cancellation. When a radio is equipped with two microphones, one microphone is designed for capturing the operator’s voice (plus the environmental noise), and the other microphone as a noise reference. The dual mic cancellation software uses the noise reference signal for filtering the noisy speech signal. This module is effective at removing directional non-stationary noise sources. A single channel noise reduction algorithm can then be applied to the output of the dual mic noise cancellation for attenuation of quasi-stationary noise components.
Another useful algorithm for radio applications is voice activated transmission (VOX). This software feature is not just an energy level detector, it is designed to trigger specifically on voice signals. When it has been determined that there is a voice signal present, then it will provide an indication to the radio module to transmit audio.
Generally, radio communications are half-duplex, but some applications have full duplex requirements. In this case, acoustic echo cancellation (AEC) software will also be required to remove the acoustic coupling between the loudspeaker and microphone.
Finally, automatic gain control (AGC) and dynamic range compression (DRC), should be applied to the receive path to ensure consistent audio levels out of the radio’s loudspeakers.
