Simulation of low-pass hearing loss in a Finnish speech discrimination test

Three different degrees of clinical hearing loss of low-pass type were stimulated by a filter apparatus. The equipment to simulate a given hearing loss is described. The speech discrimination curves corresponding to the normal hearing and to the three degrees of hearing loss were measured in normal hearing adults using Finnish PB-words. The stimulation of a light hearing loss of low-pass type yielded a two-staged discrimination curve. The discrimination curves of a moderate and a severe hearing loss crossed at a very high output level. The cause of this phenomenon is discussed on the ground of the exceptional vowel/consonant relation and intensity/frequency distribution in the Finnish language.