Simultaneous and forward masking of vowels and stop consonants: Effects of age, hearing loss, and spectral shaping

Abstract

Fluctuating noise, common in everyday environments, has the potential to mask acoustic cues important for speech recognition. This study examined the extent to which acoustic cues for perception of vowels and stop consonants differ in their susceptibility to simultaneous and forward masking. Younger normal-hearing, older normal-hearing, and older hearing-impaired adults identified initial and final consonants or vowels in noise-masked syllables that had been spectrally shaped. The amount of shaping was determined by subjects' audiometric thresholds. A second group of younger adults with normal hearing was tested with spectral shaping determined by the mean audiogram of the hearing-impaired group. Stimulus timing ensured that the final 10, 40, or 100 ms of the syllable occurred after the masker offset. Results demonstrated that participants benefited from short temporal delays between the noise and speech for vowel identification, but required longer delays for stop consonant identification. Older adults with normal and impaired hearing, with sufficient audibility, required longer delays to obtain performance equivalent to that of the younger adults. Overall, these results demonstrate that in forward masking conditions, younger listeners can successfully identify vowels during short temporal intervals (i.e., one unmasked pitch period), with longer durations required for consonants and for older adults.

Effect of Forward Masking on Frequency Following Response as a Function of Age

“…Considering auditory-evoked potentials, latency shifts in noise presentation characterizes forward masking and may be due to the delay of the auditory nervous system to recover from a previous masking stimulus. Studies on forward masking (Grose et al; 11 Fogerty et al; 5 Mehraei et al; 17 Hodge et al) 14 have reported the influence of the noise on evoked responses, regardless of the stimulus, population, and acquisition criteria that have been used. In the present data, forward masking was identified on all waves (PV, A, PX, PY, PW, PZ, and O waves) for all groups.…”

“…Masking caused by a noisy environment compromises speech comprehension because noise can potentially degrade the temporal structures of acoustic information, making discourse unintelligible (Mehraei et al; 17 Pienkowski) 21 . Recognizing speech in noisy settings is related to the ability of temporal auditory processing (Anderson and Kraus; 1 Mamo et al; 16 Fogerty et al) 5 , which is defined as the ability of the auditory system to perceive and differentiate stimuli and their acoustic characteristics over time (Terto and Lemos.) 29 Results of psychophysical (Grose and Mamo) 8 and electrophysiological tests (Grose and Mamo; 7 Anderson and Kraus; 1 Clinard and Tremblay) 2 revealed deficits in temporal auditory processing as a function of age, manifesting as a decreased capacity to follow temporal changes in speech characteristics.…”

“…Several studies have investigated speech comprehension in a noisy environment, primarily in senior individuals, who, even with normal hearing, complain of misunderstanding speech in the presence of noise (Grose et al; 10 Anderson and Kraus; 1 Grose et al; 11 Mamo et al; 16 Schoof and Rosen; 26 Fogerty et al; 5 Hodge et al). 14 Helfer and Vargo 13 suggested that hearing skills might already be affected in middle-age individuals.…”

“…4 Forward masking is related to temporal auditory processing and, consequently, speech perception in noisy environments. A common complaint of senior listeners, even those whose hearing thresholds are within normal values, is the difficulty to understand in noisy environments (Grose et al; 9 Mamo et al; 16 Schoof and Rosen; 26 Fogerty et al; 5 Pienkowski). 21 Psychoacoustic (Grose and Mamo; 8 Grose et al) 9 and electrophysiological tests (Grose and Mamo; 7 Anderson and Kraus; 1 Clinard and Tremblay) 2 have been applied to understand speech in noise.…”

“…Both components consist of complex waves that reflect neural activity, and their latencies and amplitudes can be measured and analyzed (Skoe and Kraus). 27 A number of studies (Grose et al; 10 Mamo et al; 16 Schoof and Rosen; 26 Fogerty et al; 5 Hodge et al) 14 has assessed electrophysiological responses in old listeners in the presence of noise and exhibited age-related degradation in the temporal aspects of speech decoding. Regarding forward masking, for example, Hodge et al (2018) found it more evident for the senior population.…”