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SPECTRAL AUDIO PROCESSING EXPLAINED

A06 - Ask the Experts

Q: I’m replacing my older FM audio processor and keep running into a term that I hadn’t heard before when I last shopped for an audio processor ten or more years ago. What is “spectral audio processing?”

A: It’s a unique approach to audio processing that takes into account how the human ear interprets audio and how we can use those psychoacoustic laws of physics to mask the unwanted artifacts of peak control and to bring out subtle audio details. Audio researchers tell us that our auditory system can be modeled as a filter bank with 25 overlapping bandpass filters. These are known as critical bands, and by modeling limiting based on a similar band structure, we can not only surgically limit overshoots without affecting nearby frequencies, but we can uncloak audio details that we couldn’t otherwise.

This is because limiting a signal in one narrow band psychoacoustically (not electrically) raises the perceived loudness of subtle audio details residing near to the band in limiting. Even though the audio signals in the bands adjacent to the one in limiting have not undergone any modification, our brain decodes it very differently and allows us to hear subtle details in the program material. Jeff Keith, our senior product development engineer, explains it all in his paper Critical Band Theory of Spectral Audio Processing. As you might have guessed, our new Neuron FM/HD/DAB+ processor is based on the critical band theory of spectral audio processing. You’ll be glad to know that spectral processing isn’t the only thing that’s changed since you last purchased an FM processor. The price of our Neuron processor is half what you might have paid back in the day for a top-line audio processor.

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