[Discrimination and critical signal to noise ratio of normal and pathological hearing (author's transl)].

With reference to the cocktail party situation the selective hearing of normal and pathological hearing was examined during a period of monaural or binaural noise representation. To describe the physiological situation we modified the physical definition of the signal to noise ratio adding the word "critical". Procedure of examination: Hearing level and speech intensity for maximum discrimination of numbers, monosyllables and sentences was evaluated. The speech intensity level defined by these measurements was fixed while the noise level was raised till speech discrimination was reduced to 35-45%. This value is characteristic for the critical signal to noise ratio. A second measurement examined the change of the critical signal to noise ratio by representing the same noise to the contralateral ear. Thus noise is lateralized in the middle of the head and speech discrimination is better in normal hearing compared to the monaural situation. Results of normal and pathological hearing are discussed and dependences between selective hearing and critical signal to noise ratio are shown.