Physical Measurements of Audition and Their Bearing on the Theory of Hearing

The author states his purpose to be the presentation of certain facts of audition which have been determined recently with considerable accuracy and the discussion of the theory which best explains these facts. Making use of data of Knudsen's as well as his own measurements of the auditory sensation area, the author estimates that the normal ear can perceive approximately 300,000 different pure tones. This is taking account of all possible variations in both pitch and intensity. Knudsen's data show that for considerable ranges the minimum perceptible difference in intensity bears a constant ratio to the intensity and the minimum perceptible difference in frequency bears a constant ratio to the frequency. These relations have been termed by psychologists " T h e Law of Weber and Fechner." A loudness scale is proposed such that the difference in loudness between two tones is equal to ten times the common logarithm of their intensity ratio. A pitch scale is proposed such that the difference in pitch is equal to one hundred times the logarithm to the base two of the frequency ratio. A method for measuring the loudness of complex sounds is mentioned but is to be discussed in a later paper. A method is proposed for expressing quantitatively different degrees of deafness. Reference is made to data obtained by the author on the masking of one pure tone by another. The minimum audible intensity of a pure tone depends upon the presence of another tone of different frequency. A low pitched note will, in general, exert a surprisingly large masking effect upon notes of higher frequency.