Non-native speech perception in adverse conditions: A review <s> Reverberation <s> Speech perception was studied with normal and hearing-impaired subjects in a single sound-treated room at reverberation times T = 0.3 and 0.6 seconds. Binaural and monaural perception through heari... <s> BIB001 </s> Non-native speech perception in adverse conditions: A review <s> Reverberation <s> The Modified Rhyme Test (MRT) was processed through a room (volume 165 m3, reverberation time T = 0.4, 0.8, and 1.2 s). For both binaural and monaural earphone listening the tests were recorded with a manikin (Kemar) and equalization filters to compensate for the ear canal effect. Six groups of subjects, ten subjects each, had mean ages of 10, 27, 42, 54, 64 and 72 years and average hearing threshold levels. HTLs (for 0.5, 1, and 2 kHz) of 2.7, 5.6, 6.0, 10.9, 14.4, 17.5 dB, respectively. The individual scores for the MRT without reverberation were between 90% and 100% at 70 dB SPL. Children and the elderly required from 10 to 20 dB higher SPLs than young adults to obtain maximum scores. An analysis of variance showed that all the main effects: T, age, and monaural versus binaural listening were significant. The scores declined with T for all ages. The best scores were obtained by the young adults (27 year olds). The binaural scores were about 5% better than monaural scores. Factors contributing to the results and practical implications for amplification are discussed. <s> BIB002 </s> Non-native speech perception in adverse conditions: A review <s> Reverberation <s> Recordings of nonsense syllables (VCV construction) were presented to groups of children aged 5, 7, 9, 11, and 13 years and young adults under monaural (reverberation time = 0.6s) and binaural (reverberation times = 0, 0.4, and 0.6 s) conditions of reverberation. Phoneme identification performance was affected by age, reverberation, and mode of presentation (monaural versus binaural). The major findings were (1) phoneme identification scores in reverberant conditions improved with increasing age and decreased with increased reverberation time; (2) children's performance in reverberant conditions did not reach asymptote until age 13; (3) binaural performance was consistently better than monaural performance for all age groups, with 5-year-olds showing the largest binaural advantage. <s> BIB003 </s> Non-native speech perception in adverse conditions: A review <s> Reverberation <s> Vowel identification in quiet, noise, and reverberation was tested with 40 subjects who varied in age and hearing level. Stimuli were 15 English vowels spoken in a (b-t) context in a carrier sentence, which were degraded by reverberation or noise (a babble of 12 voices). Vowel identification scores were correlated with various measures of hearing loss and with age. The mean of four hearing levels at 0.5, 1, 2, and 4 kHz, termed HTL4, produced the highest correlation coefficients in all three listening conditions. The correlation with age was smaller than with HTL4 and significant only for the degraded vowels. Further analyses were performed for subjects assigned to four groups on the basis of the amount of hearing loss. In noise, performance of all four groups was significantly different, whereas, in both quiet and reverberation, only the group with the greatest hearing loss performed differently from the other groups. The relationship among hearing loss, age, and number and type of errors is discussed in light of acoustic cues available for vowel identification. <s> BIB004
Sound reaching the listener from indirect paths following reflections contributes reverberant energy to the direct signal received at the ear. This additional energy can lead to masking of speech components. However, unlike additive noise, reverberant energy is correlated with the sound source which produced it, leading to different masking patterns. Fig. 2 depicts the effect of moderate and high levels of reverberation on the utterance used in the previous section. These examples were produced by recording the clean signal reproduced over loudspeakers in a games room and a bathroom. Reverberation smears energy in time, enhancing "horizontal" structures such as static formants and blurring "vertical" structure such as bursts and abrupt transitions. The effects of reverberation are felt as both within-and across-segment distortions. Information conveyed by time-synchronous activity is particularly affected: offsets are less precise and bursts are smoothed. Vertical structure cueing the /t/ burst in travels is absent even in moderate reverberation. Onsets are affected to a lesser extent, particularly when the dominant frequency components of the preceding sound occupy a different part of the spectrum. For example, formant onsets in show are well-preserved in moderate reverberation, although in the high reverberation condition energy arriving from the previous word blurs the inter-word boundary. Low-energy regions such as those resulting from plosive closures are susceptible to energy invading from preceding segments (see, for example, the initial weak fricative in fear). Within segments, formant transitions are broadened and, in the limit, transitional information is lost altogether. The second formant of the diphthong in show provides evidence of these kinds of distortion. By contrast, static vowel formants are enhanced and vowel identification typically suffers little in reverberation BIB004 . Reverberation affects prosodic as well as segmental information. Temporal smearing reduces the availability of cues to duration and rhythm. Information about F0 is distorted in both the low frequency region, where the motion of resolved harmonics is affected in the same way as formant transitions, and also at higher frequencies, where the modulation depth of amplitude changes at the period of the fundamental is reduced. The disruption of harmonic relationships is particularly evident in the more severe reverberation condition shown in Fig. 2 . The effects of reverberation are particularly detri- Fig. 2 . Auditory spectrograms of the utterance "his travels show in our fear" recorded in near-anechoic conditions (top), then reproduced via loudspeakers and recorded in a 5 Â 9 m games room (middle) and a 7 Â 3 m bathroom (lower). mental to speech perception in children BIB003 , listeners with hearing impairment BIB001 and older listeners BIB002 .