Non-native speech perception in adverse conditions: A review <s> Non-native speech perception under reverberation <s> Speech perception in reverberation was compared for native English speaking and non‐native listeners. The Modified Rhyme Test was recorded with reverberation times (T) of 0.4, 0.8, and1.2 s. Testing was monaural. The mean word identification scores without reverberation were similar for both groups. With T=0.8 and 1.2 s, non‐native listeners scored 10% lower than the native listeners. These results indicate that non‐native listeners who understand English very well in the absence of reverberation might have difficulty understanding speech in the presence of even moderate reverberation. <s> BIB001 </s> Non-native speech perception in adverse conditions: A review <s> Non-native speech perception under reverberation <s> English consonant recognition in undegraded and degraded listening conditions was compared for listeners whose primary language was either Japanese or American English. There were ten subjects in each of the two groups, termed the non-native (Japanese) and the native (American) subjects, respectively. The Modified Rhyme Test was degraded either by a babble of voices (S/N = -3 dB) or by a room reverberation (reverberation time, T = 1.2 s). The Japanese subjects performed at a lower level than the American subjects in both noise and reverberation, although the performance difference in the undegraded, quiet condition was relatively small. There was no difference between the scores obtained in noise and in reverberation for either group. A limited-error analysis revealed some differences in type of errors for the groups of listeners. Implications of the results are discussed in terms of the effects of degraded listening conditions on non-native listeners' speech perception. <s> BIB002 </s> Non-native speech perception in adverse conditions: A review <s> Non-native speech perception under reverberation <s> Recent evidence on the perceptual performance of bilingual listeners suggests that a nonaudibility-based cost exists in processing a second language. That is, when compared to monolingual English speakers and early bilinguals, listeners who acquired English as a second language after puberty show reduced performance when listening to the second language in background noise, despite normal auditory thresholds. However, past studies have not controlled for the homogeneity of the bilingual participants used in auditory research; therefore, it is unknown whether the deficit observed in bilingual function is due to a lack of control for language-related variables. The ability of a homogeneous group of Spanish-English bilinguals and English monolingual listeners to perceive sentences in quiet and in noise at threshold levels was evaluated using the Hearing in Noise Test (HINT). Both groups performed similarly in quiet conditions. In the noise conditions, the bilingual group's performance was significantly poorer than the monolingual group's performance. However, both groups showed a binaural advantage of 7-8 dB when the signal and noise were separated by 90 degrees. <s> BIB003 </s> Non-native speech perception in adverse conditions: A review <s> Non-native speech perception under reverberation <s> In an ideal "reverberant" room, the energy of the impulse responses decays smoothly, at a constant rate of dB/s, so that gradually-decaying tails are added at the ends of sounds. Conversely, a single echo gives a flat energy-decay up to the echo's arrival time, which then drops abruptly, so that sounds with only echoes lack the decaying-tail feature of reverberation. The perceptual effects of these types of reflection pattern were measured with test-words from a continuum of steps between "sir" and "stir", which were each embedded in a carrier phrase. When the proportion of reflected sound in test-words is increased, to a level above the amount in the carrier, the test words sound more like "sir". However, when the proportion of reflected sound in the carrier is also increased, to match the amount in the test word, there can be a perceptual compensation where test words sound more like "stir" again. A reference condition used real-room reverberation from recordings at different source to receiver distances. In a synthetic-reverberation condition, the reflection pattern was from a "colorless" impulse response, comprising exponentially-decaying reflections that were spaced at intervals. In a synthetic-echo condition, the reflection pattern was obtained from the synthetic reverberation by removing the intervals between reflections before delaying the resulting cluster relative to the direct sound. Compensation occurred in the reference condition and in different types of synthetic reverberation, but not in synthetic-echo conditions. This result indicates that the presence of tails from reverberation informs the compensation mechanism. <s> BIB004 </s> Non-native speech perception in adverse conditions: A review <s> Non-native speech perception under reverberation <s> This study compared monosyllabic word recognition in quiet, noise, and noise with reverberation for 15 monolingual American English speakers and 12 Spanish–English bilinguals who had learned English prior to 6 years of age and spoke English without a noticeable foreign accent. Significantly poorer word recognition scores were obtained for the bilingual listeners than for the monolingual listeners under conditions of noise and noise with reverberation, but not in quiet. Although bilinguals with little or no foreign accent in their second language are often assumed by their peers, or their clinicians in the case of hearing loss, to be identical in perceptual abilities to monolinguals, the present data suggest that they may have greater difficulty in recognizing words in noisy or reverberant listening environments. <s> BIB005
Compared to additive noise, relatively few studies have considered the effect of reverberation on non-native listeners BIB001 BIB002 BIB005 . Of these, only the latter examined the most common listening situation in which the effects of noise and reverberation are combined. Using a consonant identification task, BIB001 and BIB002 demonstrated that non-native listeners who performed at comparable levels to natives in anechoic conditions suffer substantially more in the presence of mild, moderate and severe reverberation, with the native advantage reaching a peak for the moderate level of reverberation. This finding contrasts with the additive noise case for consonants, described above, where no interaction of nativeness and noise level is typically observed. Indeed, BIB005 found no significant additional effect of reverberation on monosyllabic word recognition in speech-shaped noise for bilingual listeners who had learned English prior to the age of six. It is not clear why reverberation might have a disproportionate impact on non-native listeners for tasks which focus on acoustic information at the segmental level while additive noise does not. In fact, since reverberation is a universally-experienced feature which listeners appear to compensate for, at least in part BIB004 , it might be expected to have similar effects on all listener groups. A comparison can be made with the use of low-level cues such as spatial separation BIB003  or F0 by non-native listeners, where no native advantage has been found. The suggestion that higher-level linguistic knowledge is required to mitigate the impact of reverberation would be an interesting finding. Given the level of reverberation in typical instructional settings (see Section 1), this is an area where further studies are needed with a wider variety of listener groups and tasks.