Effects of spectral smearing on speech perception

Connected speech presented in quiet is highly redundant. For such a condition, the resolution of spectral contrasts by the ear seems to be much larger than would be required. This suggests that the ear's high selectivity in frequency is particularly important to understanding speech in the presence of interfering sounds. The effect of reduced frequency resolution on the speech‐reception threshold (SRT) for sentences in noise was investigated for eight normal‐hearing subjects by simulating an auditory system with variable frequency selectivity. Signal processing was performed by short‐time fast Fourier transforms (FFT), reduction of contrast in the spectral envelope without affecting the harmonic structure, and overlapping additions to reconstruct a continuous signal. The Spectral envelope in the frequency region from 100 to 8000 Hz was smeared over fixed relative bandwidths of 1/8, 1/4, 1/2, 1, 2, 4, and 8 octaves. Results show that the SRT increases progressively as the spectral envelope is smeared over bandwidths exceeding the ear's critical bandwidth. In a second experiment phoneme, confusions as a result of three different degrees of spectral smearing are studied in nonsense CVC syllables.Connected speech presented in quiet is highly redundant. For such a condition, the resolution of spectral contrasts by the ear seems to be much larger than would be required. This suggests that the ear's high selectivity in frequency is particularly important to understanding speech in the presence of interfering sounds. The effect of reduced frequency resolution on the speech‐reception threshold (SRT) for sentences in noise was investigated for eight normal‐hearing subjects by simulating an auditory system with variable frequency selectivity. Signal processing was performed by short‐time fast Fourier transforms (FFT), reduction of contrast in the spectral envelope without affecting the harmonic structure, and overlapping additions to reconstruct a continuous signal. The Spectral envelope in the frequency region from 100 to 8000 Hz was smeared over fixed relative bandwidths of 1/8, 1/4, 1/2, 1, 2, 4, and 8 octaves. Results show that the SRT increases progressively as the spectral envelope is smeared over ...