Glossary

The reference point for the threshold of hearing, equal to 20 micro PA (micro Pascals rms).

1/3-octave expresses the bandwidth of equalizers and other filters that are 1/3-octave wide at their -3 dB (half-power) points. It also Approximates the smallest region (bandwidth) humans reliably detect change. 

3D-Sound describes a three-dimensional sound field. A true 3D sound field positions sound anywhere desired in a semi-spherical shell surrounding the listener. Sound must be able to come from anywhere within this half sphere to point exactly to it with closed eyes. If it does not, it is not 3D sound. 

A comparison testing methodology between two components. Usually a side by side comparison of two different speakers or amplifiers. Also see ABX test comparison.

(BPF) — A filter that removes or attenuates frequencies above and below the cutoff frequencies at which it is set, and only passes a specific frequency band. The bandpass frequencies are normally associated with frequencies that define the half power points, i.e. the -3 dB points.