Levels is a multimedia project involving the measurement of energy found in various physical phenomena such as sound and electromagnetic radiation (radio waves, light, etc).

Its current manifestation is a collection of octave files or levels000.zip


To get a feel of Octave's syntax, take a look at tonetest.m. In octave, variables can be scalars, vectors or matrices. Audio signals are typically stored as a vector (1 dimensional arrays of numbers) whose elements can be accessed by a vector index. In tonetest.m the variables n and index are vectors.

Frequency dependent energy is found in sound.

Using frequency selective filters, one may apply gain or reduction on acoustic energy over a selected range of frequencies. In addition, this gain may be varied over time based on the analysis of the signal. By providing a time varying gain we may make soft passages softer and louder passages louder. Doing so lowers the perceived noise floor and simultaneously provides a dynamic range that exists in real life but is lost by recording equipment.

For example, if the audio signal has a predominance of energy at lower frequencies (like an upright bass produces), then we can apply a filter to isolate the low frequencies and then apply a time varying gain to just the low frequencies- the result is a 'smooth and clean' sounding bass that sits where it should in the mix.

Using the idea of frequency selective, time varying gain, we can effect different portions of the audible frequency range uniquely and increase the overall perceived level in a more pleasing way. While beauty is in the eye of the beholder, there are some fundamentals associated with applying frequency selective, dynamic (time varying) gain during the mastering phase of a recording:



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