A life-sized physical model of the human cochlea is demonstrated. The model consists of two fluid-filled chambers separated by a polymer membrane and connected through a small hole that serves the same functional purpose as the helicotrema. The dimensions of the two chambers were made identical to those of scala vestibuli and scala tympani in the real cochlea. The membrane's width and length are the same as the values measured for the biological basilar membranes, and its thickness is chosen to give it appropriate rigidity. A piezoelectric transducer drives the system via an elastic window (acting as the oval window) on one side of the scala vestibuli. The resulting vibration pattern on the basilar membrane is investigated with an optical novelty filter, with detection sensitivity of 0.3 A at 2 kHz with a 1-Hz bandwidth. The overall response of this model is found to be a good extrapolation of Bekesy's low-frequency data. However, the tuning curves of this model are not as sharp as those found by Rhode, Johnstone, and others from the in vivo measurements. Possible implications of these results are discussed.

No abstract

Speech intelligibility scores from 16 subjects with sensorineural hearing loss were evaluated using a digitized version of the California Consonant Test that was presented via headphones through a 300 to 3000 Hz bandpass filter to simulate the telephone band. Each subject was tested with an unprocessed signal that was frequency-equalized to compensate for the individual's hearing loss, and a signal that was equalized and compressed by the use of a compressor compression technique. Subjects were tested at three sound pressure levels above a pure-tone average threshold for frequencies 1 and 2 kHz. Two digital signal processing techniques designed to compensate for high-frequency hearing loss were examined: frequency domain processing and time domain processing. Frequency domain involved modification of the short-term spectrum obtained through a fast Fourier transform, whereas time domain processing involved passing the signal through a bank of finite impulse response filters. Both techniques showed significant intelligibility improvements (15-3070). In a second experiment, 16 additional subjects with high-frequency hearing loss compared an amplified telephone signal to three processed signals: (1) 6 dB per octave emphasis; (2) a signal frequency equalized for their hearing loss; and (3) a signal that was equalized for their hearing loss and was compressed according to their uncomfortable loudness levels. Most subjects preferred the signal with the 6 dB per octave emphasis. (Ear Hear 13 2:70-79)

No abstract