The 1920 decade was dominated by new and improved instrumentation and by the Bell Telephone Laboratory program that undertook to measure (physically) speech, hearing, music, noise, and (with E. P. Fowler, Sr.) abnormal hearing. It also introduced syllable articulation and sentence intelligibility tests. Harvey Fletcher summarized all this inSpeech and Hearingin 1929. In 1928 Georg V. Békésy described the traveling wave pattern on the cochlear partition, and in 1930 E. G. Wever and C. W. Bray listened to the electrical output of a cat's auditory nerve. These events initiated a whole new era in the bioacoustics of the ear and the electrophysiology of the auditory system. Psychoacoustic topics of interest included masking, lateralization, combination tones, and subjective scales of pitch and loudness. The different approaches were correlated by S. S. Stevens and H. Davis inHearingin 1938.