Noise audiometry

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The noise audiometry according to Langenbeck is an audiometric method of ear, nose and throat medicine , with which the hearing threshold for tones in a masking noise is determined. The test allows conclusions to be drawn about the location of the damage in the case of sensorineural hearing loss .

The research method was presented by Bernhard Langenbeck (* May 25, 1895 in Osterode am Harz, † April 29, 1964 in Bonn) in 1949 and 1950 in several publications and later scientifically processed.

Figure 1: Example of a hearing threshold for high-frequency hearing loss in relative representation (black) and absolute representation (blue)
Figure 2: Noise audiometry according to Langenbeck: absolute (blue) and relative (light gray) representation of the tone audiogram, masking with white noise 30 dB (pink)
Figure 4: Noise audiometry according to Langenbeck: Absolute representation of the quiet hearing threshold (blue), masking with white noise 30 dB (pink). The clear tone points are below the level of the noise level and avoid the uncovered quiet threshold: neural hearing loss

Investigation process

To carry out the test, a tone audiometer is required that can offer broadband noise of variable intensity at the same time as the sinus tone on the same ear . According to Langenbeck, the hearing threshold is first determined without masking noise ( quiet hearing threshold ) and entered as the absolute hearing threshold so that the normal hearing threshold in the lower and higher frequencies is not 0  dB , but rather higher values, which also applies analogously to a non-normal audiogram ( Illustration 1). The absolute representation of the hearing threshold curve was used by Langenbeck because “this representation alone gives clear relationships”.

The relative representation is normally used on the tone audiogram form, the normal hearing threshold is shown as a straight line and the level at the normal hearing threshold is referred to as 0 dB, regardless of the fact that the sound pressure level required to reach the hearing threshold is higher in the low and high tones than at 1-4  kHz . This dB designation is therefore also known as dB HL (from hearing level ), in contrast to dB SPL (from sound pressure level ), the absolute dB number of the sound pressure level .

White noise is now offered, the intensity of which is selected so that parts of the quiet hearing threshold are covered by the noise, but other parts are not, usually parts of the hearing threshold in the low and high frequency range. The absolute representation of the hearing threshold allows the corresponding level of the noise to be entered in the form as a straight line (Figure 2).

If the noise continues to be offered, a tone audiometric hearing threshold determination is carried out again, but now in the area of ​​the hidden quiet tone threshold it is only possible to hear the tone when the level of the masking noise is reached. The appearance of the tone out of the noise can be specified very precisely by the normal hearing person. According to Langenbeck, one speaks of the clear tone point . Where the quiet hearing threshold is not covered by the noise, the same hearing threshold is given as in the examination without masking noise, so the straight line of the clear tone points ends in the quiet hearing threshold in the range of low and high tones.

Examination result

In the case of cochlear hearing loss (hair cell damage), the clear tone curve behaves like that of people with normal hearing, the clear tone points are at the level of the noise level and lead to the uncovered quiet hearing threshold in the low and high tones

In the case of neural hearing impairment, the clear tone points are only audible at a level higher than the noise level, i.e. they are below the level of the noise level and avoid the uncovered quiet hearing threshold (Figure 4).

Noise audiometry with modern audiometers

Modern tone audiometers do not have the possibility of an absolute representation of the hearing threshold curve. In order to be able to carry out a noise audiometry with the relative representation, one has to limit oneself to the frequencies 1 to 4 kHz, since there is practically no difference to the absolute representation. If possible, broadband noise should be used; when using narrowband noise, as it is also used for masking in tone audiometry, it should be noted that in the higher frequency range the narrowband noise increasingly assumes a tonal character and the recognizability of tones is more difficult. A reference point is set on the quiet hearing threshold (mostly at 4 kHz) and the noise level is then set. As with the procedure for the absolute display, the clear tone points are now searched for, but only in the range between 1 and 4 kHz, and the behavior of the clear tone curve in the area of ​​the reference point of the resting hearing threshold is determined (confluence or evasion).

swell

  1. ^ Bernhard Langenbeck: The noise audiometry as a diagnostic method . In: Journal of Laryngology, Rhinology, Otology and their Frontier Areas . tape 29 , 1950, ISSN  0044-3018 , p. 103 .
  2. ^ Bernhard Langenbeck: Noise audiometric diagnosis. The absolute evaluation . In: Archives for ear, nose and larynx medicine . tape 158 , 1950, ISSN  0365-5245 , p. 458-471 , doi : 10.1007 / BF02121706 .
  3. ↑ Bernhard Langenbeck: Guide to practical audiometry . 2nd, improved edition. Georg Thieme Verlag, Stuttgart 1956, DNB  452709466 .
  4. ↑ Ernst Lehnhardt , Roland Laszig (Ed.): Practice of Audiometry . 8th edition. Thieme, Stuttgart 2001, ISBN 3-13-369008-6 .


literature

  • E. Lehnhardt, R. Laszig (Ed.): Practice of Audiometry. 9., completely revised. Edition. Thieme, Stuttgart 2009, ISBN 978-3-13-369009-6 .