Audio processing explained
Most FM broadcasting transmission chains have at least a basic degree of audio processing included, in order to improve the audio loudness. The reason for this is related to the radio listeners’ typical environment: driving in the car, cooking in the kitchen, working in a factory, etc. These environments can be loud and radio audio needs to help to cut through this!
While this is the main reason for audio processing, it is also used for:
- Consistent levels – so listeners don’t have to adjust the volume constantly
- Consistent sonic signature/EQ – so a radio station can have a unique sound that is appropriate for their format of music
- Optimization of the signal to noise ratio of the channel
- Controlling the interference of neighboring radio stations through peak and bandwidth limiting
What is audio processing?
Audio processing uses a combination of compression and limiting to lower the dynamic range, reducing the peak to average the ratio of the audio at each subsequent stage.
1. Compression stage
Compression reduces the dynamic range of the audio slowly, in a manner similar to an operator riding the gain. Compression is usually performed on the RMS level of the audio waveform and is usually gated to prevent ‘suck-up’ of noise during silence or quiet periods. In addition, compression is usually multi-band.
2. Limiting stage
Limiting has faster action and higher ratios than compression. Audio is split into several frequency bands (often 4 or more) so that bass sounds, mids, and highs are processed separately. This prevents most of the problems you get with basic single-band limiters. Each band is compressed in dynamic range – the quiet parts are boosted and the loud parts reduced. It creates a denser, louder sound but can create intermodulation distortion if overdone.
3. The clipping stage – FM & AM
Removes all audio above a certain clipping threshold. Reduces the peak to average ratio of the audio dramatically. It will produce harmonic distortion, and if overused it can also produce intermodulation distortion. The clipping stage has zero time constants, so it has no effect on surrounding audio.
Why do I need audio processing at my radio station?
Most radio stations, big and small, use audio processing in order to stand out from the crowd and get more listeners. The main benefits of audio processing are listed below:
- Increase overall audio level ‘loudness’ and improve the signal to noise: makes you sound louder than other stations and jump out at listeners. Maximize the headroom in the transmission channel, moving audio as far away from the noise floor as possible, which improves the signal to noise. It also aids listener ability in vehicles by having a consistently loud sound to combat engine and road noise
- Ensure audio level consistency to aid listener experience: listeners don’t have to constantly adjust the volume of the radio.
- Over-modulation, distortion, and interference: too high audio level results in distortion in receivers and interference to neighboring FM or AM stations. Digital radio will sound terrible when 0dBFS is hit in the codec, with large amounts of distortion generated. However, too low audio level results in background noise being heard. Changing levels can result in noise, distortion, and listener adjustment
- Create a sonic signature to sound how you want to sound. A unique signature sound sets you apart from other radio stations and is something that listeners will recognize instantly
Audio processing solutions from BW Broadcast
For listeners, good radio sound is everything. It only takes them a few seconds to decide whether they want to keep listening to your station or switch to another. With the right audio processor, you can ensure a high-quality signature sound for your station and attract more listeners.
The BW Broadcast audio processors are popular among many radio stations around the world – from bigger networks such as BBC, to small community stations in Africa. These cost-effective, yet high-quality processors make sure that your audio is loud and clear. Available in different multi-band configurations for FM, AM, digital radio and web streaming.
The original DSPXmini and DSPXtra audio processors have spent the last 12 years dominating the low-cost, high-value audio processing market, offering FM, AM, and HD versions to broadcasters who need to sound the best on a budget.
The Encore versions of this industry favorite now puts all models into a single box, along with platform-wide features such as intelligent PlanB audio backup and remote control monitoring.