All broadcast broadcast networks have at least a rudimentary degree of broadcast audio processing to reduce the dynamic range of program material. Now “reduce dynamic range” might sound bad in a hi-fi sense, but don’t let that put you off. In the real world, most of your listeners are not hi-fi buffs, and furthermore, almost none of them listen in hi-fi environments. Most will listen to it as they go about their daily lives in the kitchen, in offices, in factories, driving the car, etc. These environments are “hostile” in terms of audio, so you need something that will help your station remove background noise so you can be heard.

In its simplest form, an audio processor is just an audio limiter that keeps your streams legal by preventing them from being too loud (the technical term is “excessive drift”). This is fine for legality, but it doesn’t sound good when the limiter works. You could just set your audio levels low enough that you never clip, but then your streams would sound very quiet.

The answer is multiband audio processing. Virtually all commercial and public service stations use it. The main advantage is that it increases the volume of the transmission, while avoiding excessive deflection. There are also some added benefits, however there can also be pitfalls: Streaming audio processors have many, many settings available, and when set incorrectly, can make streams exhausting to listen to – or just plain “awful”! That’s where “black art” comes in: when properly tuned broadcast audio processors can make the entire station sound better and more professional, we’re not exaggerating!

Broadcast audio processors typically have three main stages:

• AGC – Automatic Gain Control – this section acts a bit like a technical operator sitting in the studio. If the programming (or the guest) is a bit quiet, slowly and gently increase the audio level. If things are getting a bit noisy, turn it down slowly. Just this feature alone is incredibly useful on Community Radio, where many presenters are inexperienced and have poor control of their audio levels.
• Multiband Compressor or Limiter – this section is the smart part. Splits audio into multiple frequency bands (often 5 or more) so that low, mid, and high sounds are processed separately. This avoids most/all of the problems of the basic single band limiters mentioned above. Each band is dynamic range compressed, meaning quiet bits are boosted and noisy bits are cut. This is similar to the AGC above, but makes it much faster. It is in this area that the “sound signature” is created, as it can drastically alter the tonal nature of the audio.
• final limit – this is a very fast acting limiter that cuts off any remaining signal spikes to ensure your transmissions remain legal and you don’t drift too much. Non-broadcast audio processors made by some of the cheaper brands do not have this stage.

So that’s it in a nutshell. Broadcast audio processing is really important for your station. You can go for hardware broadcast audio processing units like the Orban Optmod (in your dreams!), Omnia, or the more affordable DSPX, or there are various software solutions as well. We have an audio demo of the impact of broadcast audio processing on our website. Check it out here: http://a-bc.co.uk/audio-processing/