As part of our continued effort to improve the quality of our feeds, we have started experimenting with software-based audio processing systems. Bote has come up with a very effective system of VST plugins utilizing VSThost, and they improve the listening experience tremendously by removing any audible hum, passing only voice audio-frequencies, and leveling the output so everything is at a uniform volume.
GGate
The first VST plugin used is GGate, which essentially acts as a squelch circuit by only passing audio when a preset volume level is exceeded. This helps eliminate any hum, static, etc. that is otherwise present during periods of silence between radio transmissions.
TDR Nova
The second VST plugin, TDR Nova, is an audio equalization tool used to pass only voice audio frequencies between 300 hz and 3000 hz, eliminating a lot of the noise & hums present outside of this range. As streaming audio encoding only has so much bandwidth, it is highly beneficial to remove any extra noise to ensure the best possible audio quality delivered to the end user. If the encoder is working to include all of the static in a distant, noisy transmission, then the fidelity of the actual voice audio will suffer in the encoded audio stream.
LoudMax
The final VST plugin used is LoudMax, which is a audio leveling plugin that works well with analog voice transmissions. By setting a a comfortable target output level that doesn’t fully saturate the encoder (we use -10 dB as a target), the plugin will level all audio to this target volume. In a setting like the railroad where you may have a quiet signal caller followed by someone shouting over the roar of an old standard cab locomotive, your listeners’ ears will thank you for this addition.