Ear signal

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An ear signal is the acoustic signal that appears on the eardrum and that has undergone multiple changes on its way. The word is mainly used as "ear signals" in the plural; also as HRTF = head-related transfer function or as head -related transfer function .

If the direction of the sound source is deflected to the side, the ear signals differ. The interaural characteristics are the level differences (ILD: Interaural Level Difference ) and the transit time differences (ITD: Interaural Time Difference ). In the horizontal plane, the hearing localizes on the basis of ITDs and ILDs.

With the help of an artificial head , the effective ear signals in the recording room are recorded, which in principle have to be reproduced via headphones. Ideally, the reproduced artificial head signals are identical to the ear signals that the listener would receive in the recording room.

The distance between the ears, as the crow flies, from eardrum to eardrum is about 14 cm. You have to think ahead, as if sound waves like X-rays could go straight through your head. The effective ear distance must of course be greater, as can be seen from the ILD.

There are serious restrictions for binaural recording and playback technology in practical use.

  1. The reproduction of the ear signals must be very precise; differences between the individual outer ear and the artificial head outer ear already cause impairments. Interventions such as dynamic reduction, volume adjustment, and background noises during playback also have a disadvantageous effect.
  2. In principle, the ear signals must be reproduced via headphones. So-called transauralization processes, which perform an inverse filtering of the outer ear transmission function beforehand for the loudspeaker reproduction, are not precise enough and limit the listening zone to a few centimeters.
  3. Studies have shown that the ear signals even have to be adapted to the current head position of the listener. When evaluated by the ear, the dynamic signal characteristics had a previously underestimated interpretation, especially for the correct localization in the median plane .

Ear signals are not to be equated with stereo loudspeaker signals .

"Ear signals" that are reproduced in the superimposed sound field of the two stereo speakers never match the ear signals that a corresponding sound source would generate at the location of the phantom sound source , regardless of whether an XY intensity stereophony , AB transit time stereophony , ORTF stereo system -, KFM microphone or an artificial head is used for the recording. The ear signals are neither in terms of spectral differences nor in the time domain, e.g. B. autocorrelation function and interaural cross-correlation function , compatible with a corresponding imaginary sound source.

See also

Duplex theory

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