In recording studios it is common to use equipment and algorithms to enhance audio productions in the low frequency range. Today’s methods use either a frequency-selective dynamic compression or focus on psychoacoustics to take advantage of the residuum effect. The basic subject of this paper is a method to generate sub-harmonics of an audio signal. The most interesting sub-harmonic is one octave below a signal´s fundamental frequency. By implementing a mathematical formula it is possible to produce an oscillation at half the frequency of a given harmonic oscillation. The method works in the analog or digital domain and instantaneous, which makes it suited for real-time applications of musicians. Depending on the design the process can be optimized for stationary signals or for signals with transient components.
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