OBJECTIVES: 1. To study auditory patterns and levels of processing in the perception of complex signals and speech, through psychophysical studies of discrimination and recognition. 2. To inter-relate different representation of Bekesy traveling wave in cochlear transduction, and to study tuning mechanisms in neural encoding, through physiological studies of cochlear microphonic and of single auditory neurons. 3. To learn basic properties of simple auditory learning and to relate the perception of sound-spectral qualities to cochlear function in animals and humans by developmental and comparative studies, through conditioning procedures. 4. To discover mechanisms of the effects of noise on hearing through study of discrepancies among anatomical, physiological, and behavioral results, by means of histological analysis, electrical responses of auditory neurons, and conditioned-response audiometry. 5. To develop and evaluate a hearing aid with frequency-selective gain and limiting, to study the tactile perception of speech as an aid to lipreading, and to discover the principles underlying the visual perception of speech, through computer and electroacoustic engineering and psychophysical application to audiological procedures. 6. To extend brainstem electric-response audiometry to a full-frequency audiogram, to categorize phonologically the speech-production characteristics of hearing-impaired children through spectrographic analysis and to quantify their stages of language development through development and standardization of a language scale.