Level difference
The word level difference or level difference is used in two different areas:
- in auditory perception in natural directional hearing as a frequency- dependent ILD ( Interaural Level Difference)
- in audio engineering as a frequency-neutral ΔL when generating the direction of the audio event as loudspeaker signals between the stereo loudspeakers, i.e. on the loudspeaker basis (see also interchannel ).
In both cases, the level difference is usually given in decibels (dB).
The interaural level difference ILD
With the help of the level , d. H. the volume difference, the azimuth of a sound source can be determined between the right and left ear : if a sound comes from the left side, it appears louder to the left ear; in the right ear the sound is quieter because it is further away from the sound source and in the acoustic shadow of the head. The level difference is therefore dependent on the distances traveled by the sound.
If the sound source is exactly in front of or behind the hearing person (middle of the head), there are no level differences. In this case the sound paths are the same length.
Even small deviations of a sound source from the center of the head can be detected. In the case of small changes in sound (e.g. clicks ), level differences can be distinguished that arise when the sound source deviates at an angle of around 3 ° from the center of the head. The localization is significantly improved when the head is moved.
The level difference is frequency-dependent: tones above 1 kHz are reflected from the head. At 10 kHz the level difference can be up to 20 dB. The discrimination performance (the ability to differentiate between stimuli or signals) is worst between 1.5 and 3.0 kHz and greatest for complex tones with fluctuations in intensity .
The duplex theory says something about the interaural level difference and contributes significantly to the understanding of the process in natural human hearing.
The interchannel level difference ΔL
With the level differences of panorama controls (panpots) in mixing consoles , the direction of the auditory events of the phantom sound sources can be changed on the stereo loudspeaker basis ( intensity stereophony ). A maximum level difference of Δ L max = 18 dB (16 to 20 dB) causes the full sideways deflection from the loudspeaker direction, depending on the signal.
With the Haas effect , which plays an important role in PA sound reinforcement , the principle of opposing level difference and time delay is used as trading .
See also
literature
- Michael Dickreiter, Volker Dittel, Wolfgang Hoeg, Martin Wöhr (eds.): Handbuch der Tonstudiotechnik , 8th, revised and expanded edition, 2 volumes, publisher: Walter de Gruyter, Berlin / Boston, 2014, ISBN 978-3-11- 028978-7 or e- ISBN 978-3-11-031650-6
- Hubert Henle: The recording studio manual. Practical introduction to professional recording technology. 5th, completely revised edition. Carstensen, Munich 2001, ISBN 3-910098-19-3 .
- Siegfried Wirsum: Practical sound reinforcement technology. Device concepts, installation, optimization. Franzis-Verlag GmbH, Munich 1991, ISBN 3-7723-5862-4 .