The influence of environmental sound training on the perception of spectrally degraded speech and environmental sounds

Abstract

Perceptual training with spectrally degraded environmental sounds results in improved environmental sound identification, with benefits shown to extend to untrained speech perception as well. The present study extended those findings to examine longer-term training effects as well as effects of mere repeated exposure to sounds over time. Participants received two pretests (1 week apart) prior to a week-long environmental sound training regimen, which was followed by two posttest sessions, separated by another week without training. Spectrally degraded stimuli, processed with a four-channel vocoder, consisted of a 160-item environmental sound test, word and sentence tests, and a battery of basic auditory abilities and cognitive tests. Results indicated significant improvements in all speech and environmental sound scores between the initial pretest and the last posttest with performance increments following both exposure and training. For environmental sounds (the stimulus class that was trained), the magnitude of positive change that accompanied training was much greater than that due to exposure alone, with improvement for untrained sounds roughly comparable to the speech benefit from exposure. Additional tests of auditory and cognitive abilities showed that speech and environmental sound performance were differentially correlated with tests of spectral and temporal-fine-structure processing, whereas working memory and executive function were correlated with speech, but not environmental sound perception. These findings indicate generalizability of environmental sound training and provide a basis for implementing environmental sound training programs for cochlear implant (CI) patients.

Figure 1.

A diagram of the testing–training sequence used in the study.

Figure 2.

A schematic illustration of two stochastic frequency modulation (FM) patterns to be discriminated in a single trial. These FM patterns were obtained by using a 5-Hz low-pass noise as the modulator of a 500-ms 1-kHz pure-tone carrier with the maximum frequency excursion from the carrier fixed at 400 Hz.

Figure 3.

A schematic illustration of two spectral ripples of 0.75 cycles per octave and a 30-dB peak-to-trough-level difference. With a random starting phase at each trial, listeners discriminated stimuli based on the difference in ripple phase, which was adaptively varied to estimate the just-detectable phase difference.

Figure 4.

Performance accuracy across testing sessions for speech (speech-in-noise sentence test [SPIN-R] and consonant-nucleus-consonant monosyllabic word test [CNC]) and environmental sounds. Following environmental sound training (between Pretest 2 and Posttest), the biggest improvement is evident for environmental sounds, with both sentences and words also showing improvement to a smaller degree. Error bars represent ± 1 standard deviation.

Figure 5.

Environmental sound identification accuracy between Pretest 2 and Posttest for three sound source categories: (a) low-accuracy sounds that were later used during training (difficult-trained), (b) low-accuracy sounds that were not trained (difficult-not trained), and (c) high-accuracy sounds that were not trained (easy-not trained). Error bars represent 1 standard deviation of the mean.

Figure 6.

Identification accuracy on Pretest 2 and Posttest for the two subgroups of the difficult-trained (D-T) sound sources: difficult-trained-used (D-T-used), that is, two exemplars of each source selected for training and used during training and difficult-trained-alternative (D-T-alt), that is, two exemplars of each source selected for training but not used during training. Error bars represent 1 standard deviation of the mean.