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Classification according to ICD-10
H93.2 Other abnormal hearing sensations
ICD-10 online (WHO version 2019)

The recruitment or recruitment , German " loudness compensation" is a psychoacoustic phenomenon in diseases of the inner ear .


The outer hair cells of the inner ear can amplify low (quiet) sound and dampen strong (loud) sound. Because of the sound-amplifying effect, those who can hear well can also perceive quiet tones and, on the other hand, do not perceive loud noises as very loud and unpleasant as quickly. The damage or failure of these sensory cells causes hearing loss in the case of low sound with an increase in the hearing threshold due to the loss of amplification , on the one hand, and due to the loss of attenuation in the case of strong sound, that loud sounds are perceived faster than loud and uncomfortable. The faster increase in loudness in the remaining listening area between the hearing threshold and the discomfort threshold is referred to as recruitment .

Recruitment in everyday life

In practical life can be the example of presbycusis understand or Sozioakusis (hearing loss due to the living environment). Old and hard of hearing people often do not understand soft speech. If you then speak louder, the hard of hearing perceives it disproportionately loud and complains "Why are you screaming like that?"

While soft tones are heard differently by the hard of hearing than by the normal of hearing, there is a louder tone that is heard equally loud by the normal and hard of hearing. Hence the German term Lautheitsausgleich.

Recruitment in Medicine

Recruitment is a phenomenon of the outer hair cells and thus the inner ear. Loudness compensation means that sounds at low volume are perceived as quieter in the hard of hearing compared to the healthy ear. However, as soon as the volume of the tones is increased, the volume perception of the healthy and hard of hearing ear adjust to one another until the perception is the same. In the case of hearing impairments that first develop in the auditory nerves or in the brain (e.g. acoustic neuroma ), there is no loudness compensation; Here the hard of hearing hears even loud sounds more quietly than the normal hearing. In ear, nose and throat medicine , special hearing tests have therefore been developed that examine the presence of a recruitment. Examples are the Fowler test , the Lüscher test and the Short Increment Sensitivity Index ( SISI test ). These tests have become less important due to brain stem audiometry (FAP, BERA) and magnetic resonance imaging . A newer psychoacoustic measurement that also reveals recruitment is categorical loudness scaling .

Positive Recruitment is evidence of hearing impairment in the area of the ear = hearing loss = sensorineural hearing loss in Hörschnecken range (cochlear).

Negative recruitment (lack of recruitment) is an indication of a sensorineural disorder or nerve disorder in the retrocochlear area.


  • Ernst Lehnhardt, Roland Laszig: Practice of Audiometry . 8th edition. Thieme, Stuttgart 2001, ISBN 3-13-369008-6 .
  • Rainer Klinke, Stefan Silbernagl: Physiology . 5th edition. Thieme, Stuttgart 2005, ISBN 3-13-796003-7 .
  • Pschyrembel Clinical Dictionary . 260th edition. de Gruyter, Berlin 2004, ISBN 3-11-018201-7 .

Individual evidence

  1. Ernst Lehnhardt: Practice of Audiometry: 14 tables . Georg Thieme Verlag, 2001, ISBN 978-3-13-369008-9 , p. 48 ( limited preview in Google Book search).