Equivalence (sound engineering)

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In sound engineering, equivalence means the equivalence of running time differences and level differences in the loudspeaker signals that act in the same direction for the generation of phantom sound sources during directional listening in the stereo triangle , as is used in loudspeaker stereophony .

Basics

In the case of stereo loudspeaker signals, transit time differences and level differences in the same direction have an impact on the location of the auditory event , because both lead to a specific lateral auditory event direction as a directional deflection and localization . In order to compare the size of the two parameters , it is therefore useful to ask which transit time difference is equivalent to a specific level difference and which level difference, conversely, is equivalent to a specific transit time difference in relation to the direction of the auditory event generated. The ratio of transit time difference to level difference in μs / dB that can be determined in this way is called the equivalence factor.

This equivalence factor for stereo loudspeaker signals is approximately Δ t / Δ L = 73 μs / dB.

In the case of recordings in mixed stereophony (equivalence stereophony), these equivalence relationships apply to mutually corresponding runtime and level differences. This means that when phantom sound sources are formed, the earlier signal always interacts with the louder signal, or the delayed signal with the quieter signal in the same direction (additive). These experiments are also called matching experiments.

Trading

A clear distinction should be made between equivalence and the term trading , the opposing (subtractive) interaction of level and transit time differences, the compensation of signals. Trading and equivalence are opposites. Tonverantwortliche interested practically only the equivalence of the loudspeaker signals, because only the same direction Δ t - and Δ L - Inter Channel -Signaldifferenzen produce in stereo playback clear, unambiguous auditory events with useful localization focus .

In equivalence stereophony, on the other hand, level and transit time differences are always combined in the same direction. This means that the louder signal must always appear earlier (or the quieter signal must always appear later).

The equivalence curve and the trading curve have different origins and do not belong in a representation.

Large deviations between the test results are due to the strong inter-individual fluctuations of the test subjects, as well as the often percussive stimuli that occur in this type of experiment.

literature

Headphone lateralization in equivalence and trading: Jörg Damaschke, Michael Granzow, Helmut Riedel, Birger Kollmeier: On the equivalence of interaural time and level differences with short stimuli : (PDF; 1.9 MB)

Web links