In described examples, a method of processing an audio program material includes converting the audio program material into a frequency domain audio program material; increasing or decreasing an energy amplitude of one or more energy troughs in an audio data sample in the frequency domain audio program material, ones of the energy troughs being located between respective ones of one or more pairs of adjacent energy peaks in the audio data sample, the pairs of adjacent energy peaks selected to correspond to frequencies of sounds which were captured to create the audio program material; repeating the increasing or decreasing step for multiple audio data samples in the frequency domain audio program material; and converting the frequency domain audio program material into a time domain audio program material.