ABSTRACT
In audio engineering, it has always been important to be able to describe the frequency content of a signal. A spectrum analyzer is an important and widely used tool for this purpose. Filters with relative bandwidth especially find their way into practical sound engineering when the measurement relates to reproduced sound. The hearing more or less perceives sound in logarithmically spaced frequency bands of relative bandwidth. In room acoustics, the specification of materials’ absorption coefficients applies 1/1 octave band. Hence, it is relevant to measure the reverberation time of a room in octaves. When analyzing background noise in rooms and presenting the results in the form of noise rating or noise criterion curves, 1/1 octave-band analysis always applies. Due to the advantages of digital technology, largely no analog filters apply to measurements (although they still do for creative sound design). Most filters used for measurements build on fast Fourier Transform analysis.
