A series of experiments was performed to study the upward-spread-of-masking phenomena as it pertains to pure-tone and speech stimuli. In the initial two experiments, three maskers were employed over a 40–60-dB intensity range. They included a wide band (50–5500 Hz), a speech spectrum (50–1000 Hz), and a narrow-band (50–950 Hz) noise. All filter slopes were 48 dB/octave, except for the upper slope of the speech-spectrum noise that was 6 dB/octave. In the first experiment, pure-tone thresholds obtained by a tracking procedure revealed no spread of masking when the wide-band and speech-spectrum maskers were used. Substantial spread-of-masking effects, characterized by nonlinear threshold increments outside the spectrum of the masker, were observed with the narrow-band masker. The second experiment included three types of speech stimuli (PBs, spondees, and synthetic sentences) under the same mask conditions used with the pure tones. Threshold shifts observed for the wide- and speech-spectrum maskers were linear with the masking intensity level. However, increased shifts, attributable to spread of masking, were observed with the narrow band and progressed nonlinearly as a function of the masking level. Finally, two additional experiments, performed with two different narrow-band maskers and spondee words, provided insightful information regarding the effects of the spread of masking on speech stimuli.
A Comparative Study on the Quality of Narrow-Band and Wide-Band AMR VoLTE Calls
