Fowler test
The Fowler test (ABLB test, Alternate Binaural Loudness Balance Test) is an audiometric method of ear, nose and throat medicine , with which the loudness perception of the hearing of both ears is compared. The Fowler test can only be used in the case of unilateral or significantly different hearing impairments. The test allows conclusions to be drawn about the existence of a recruitment and thus about the location of the damage in the case of sensorineural hearing loss . It is interesting that originally the evidence of recruitment was used as a differential diagnostic means to differentiate sensorineural hearing loss from conductive hearing loss , i.e. that recruitment was considered a property of all sensorineural hearing loss. The test was published by Edmund P. Fowler in 1937.
Investigation process
To carry out the test, a tone audiometer is required, which can automatically offer a tone to both ears alternately at different volume levels . According to the test person's information, the level is now adjusted in such a way that the test person has the same loudness impression on both ears, i.e. on the normally hearing and the hard of hearing ear . This process is carried out several times, based on different volume levels. Fowler did not explain the test procedure expressis verbis , later it was suggested first to offer a tone 20 dB above the audiometric hearing threshold of the poorer ear and to level the corresponding loudness in the healthy ear. The result is entered on the tone audiogram form. This process is now repeated in 20 dB steps, so a tone 40 dB above the hearing threshold is offered next, etc.
Examination result
In the case of conductive hearing loss , in which the inner ear is completely normal, the ratio of loudness perception at the hearing threshold always remains the same, even with supra-threshold sounds. If the difference in the hearing thresholds is 40 dB, for example, this difference always remains the same even above the hearing threshold. In the case of a sensory sensation disorder with recruitment, however, the loudness relationship changes as the level rises, and the required difference in levels for the same loudness impression becomes smaller and smaller, until the same loudness impression occurs again in both ears at a certain level. This is called loudness compensation . The graphical representation on the tone audiogram form creates a fan-like image (see illustration). In the case of a retrocochlear sensorineural disorder, i.e. damage to the auditory nerve , the difference in loudness impression remains the same (as in the case of conductive hearing loss) or even increases.
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- ^ Edmund Prince Fowler: The diagnosis of diseases of the neural mechanism of hearing by the aid of sounds well above threshold . In: The Laryngoscope . tape 47 , 1937, ISSN 1531-4995 , pp. 289-300 , doi : 10.1288 / 00005537-193705000-00001 .