The effect of talker variability on word recognition in preschool children.

In a series of experiments, the authors investigated the effects of talker variability on children's word recognition. In Experiment 1, when stimuli were presented in the clear, 3- and 5-year-olds were less accurate at identifying words spoken by multiple talkers than those spoken by a single talker when the multiple-talker list was presented first. In Experiment 2, when words were presented in noise. 3-, 4-, and 5-year-olds again performed worse in the multiple-talker condition than in the single-talker condition, this time regardless of order; processing multiple talkers became easier with age. Experiment 3 showed that both children and adults were slower to repeat words from multiple-talker than those from single-talker lists. More important, children (but not adults) matched acoustic properties of the stimuli (specifically, duration). These results provide important new information about the development of talker normalization in speech perception and spoken word recognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reading voices and hearing text: Talker-specific auditory imagery in reading.

A series of experiments was conducted to determine if linguistic representations accessed during reading include auditory imagery for characteristics of a talker's voice. In 3 experiments, participants were familiarized with two talkers during a brief prerecorded conversation. One talker spoke at a fast speaking rate, and one spoke at a slow speaking rate. Each talker was identified by name. At test, participants were asked to either read aloud (Experiment 1) or silently (Experiments 1, 2, and 3) a passage that they were told was written by either the fast or the slow talker. Reading times, both silent and aloud, were significantly slower when participants thought they were reading a passage written by the slow talker than when reading a passage written by the fast talker. Reading times differed as a function of passage author more for difficult than for easy texts, and individual differences in general auditory imagery ability were related to reading times. These results suggest that readers engage in a type of auditory imagery while reading that preserves the perceptual details of an author's voice. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of stimulus variability on speech perception in listeners with hearing impairment

Traditional word-recognition tests typically use phonetically balanced (PB) word lists produced by one talker at one speaking rate. Intelligibility measures based on these tests may not adequately evaluate the perceptual processes used to perceive speech under more natural listening conditions involving many sources of stimulus variability. The purpose of this study was to examine the influence of stimulus variability and lexical difficulty on the speech-perception abilities of 17 adults with mild-to-moderate hearing loss. The effects of stimulus variability were studied by comparing word-identification performance in single-talker versus multiple-talker conditions and at different speaking rates. Lexical difficulty was assessed by comparing recognition of "easy" words (i.e., words that occur frequently and have few phonemically similar neighbors) with "hard" words (i.e., words that occur infrequently and have many similar neighbors). Subjects also completed a 20-item questionnaire to rate their speech understanding abilities in daily listening situations. Both sources of stimulus variability produced significant effects on speech intelligibility. Identification scores were poorer in the multiple-talker condition than in the single-talker condition, and word-recognition performance decreased as speaking rate increased. Lexical effects on speech intelligibility were also observed. Word-recognition performance was significantly higher for lexically easy words than lexically hard words. Finally, word-recognition performance was correlated with scores on the self-report questionnaire rating speech understanding under natural listening conditions. The pattern of results suggest that perceptually robust speech-discrimination tests are able to assess several underlying aspects of speech perception in the laboratory and clinic that appear to generalize to conditions encountered in natural listening situations where the listener is faced with many different sources of stimulus variability. That is, word-recognition performance measured under conditions where the talker varied from trial to trial was better correlated with self-reports of listening ability than was performance in a single-talker condition where variability was constrained.     

Benefits of linear amplification and multichannel compression for speech comprehension in backgrounds with spectral and temporal dips

People with cochlear hearing loss have markedly higher speech-receptions thresholds (SRTs) than normal for speech presented in background sounds with spectral and/or temporal dips. This article examines the extent to which SRTs can be improved by linear amplification with appropriate frequency-response shaping, and by fast-acting wide-dynamic-range compression amplification with one, two, four, or eight channels. Eighteen elderly subjects with moderate to severe hearing loss were tested. SRTs for sentences were measured for four background sounds, presented at a nominal level (prior to amplification) of 65 dB SPL: (1) A single female talker, digitally filtered so that the long-term average spectrum matched that of the target speech; (2) a noise with the same average spectrum as the target speech, but with the temporal envelope of the single talker; (3) a noise with the same overall spectral shape as the target speech, but filtered so as to have 4 equivalent-rectangular-bandwidth (ERB) wide spectral notches at several frequencies; (4) a noise with both spectral and temporal dips obtained by applying the temporal envelope of a single talker to speech-shaped noise [as in (2)] and then filtering that noise [as in (3)]. Mean SRTs were 5-6 dB lower (better) in all of the conditions with amplification than for unaided listening. SRTs were significantly lower for the systems with one-, four-, and eight-channel compression than for linear amplification, although the benefit, averaged across subjects, was typically only 0.5 to 0.9 dB. The lowest mean SRT (-9.9 dB, expressed as a speech-to-background ratio) was obtained for noise (4) and the system with eight-channel compression. This is about 6 dB worse than for elderly subjects with near-normal hearing, when tested without amplification. It is concluded that amplification, and especially fast-acting compression amplification, can improve the ability to understand speech in background sounds with spectral and temporal dips, but it does not restore performance to normal.     

Acoustic differences, listener expectations, and the perceptual accommodation of talker variability.

Two talkers' productions of the same phoneme may be quite different acoustically, whereas their productions of different speech sounds may be virtually identical. Despite this lack of invariance in the relationship between the speech signal and linguistic categories, listeners experience phonetic constancy across a wide range of talkers, speaking styles, linguistic contexts, and acoustic environments. The authors present evidence that perceptual sensitivity to talker variability involves an active cognitive mechanism: Listeners expecting to hear 2 different talkers differing only slightly in average pitch showed performance costs typical of adjusting to talker variability, whereas listeners hearing the same materials but expecting a single talker or given no special instructions did not show these performance costs. The authors discuss the implications for understanding phonetic constancy despite variability between talkers (and other sources of variability) and for theories of speech perception. The results provide further evidence for active, controlled processing in real-time speech perception and are consistent with a model of talker normalization that involves contextual tuning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus variability and spoken word recognition. II. The effects of age and hearing impairment

Three experiments were conducted to investigate the effects of variations in talker characteristics, speaking rate, and overall amplitude on perceptual identification in normal-hearing young (NHY), normal-hearing elderly (NHE), and hearing-impaired elderly (HIE) listeners. The three dimensions were selected because variations in voice characteristics and speaking rate affect features of speech signals that are important for word recognition while overall amplitude changes do not alter stimulus parameters that have direct effects on phonetic identification. Thus, the studies were designed to examine how variations in both phonetically relevant and irrelevant stimulus dimensions affect speech processing in a number of different populations. Age differences, as indicated by greater effects of variability for the NHE compared with the NHY listeners, were observed for mixed-talker and mixed-amplitude word lists. Effects of age-related hearing impairment, as indicated by reduced scores for the HIE compared with the NHE group, were observed for variations in speaking rate and talker characteristics. Considered together, the findings suggest that age-related changes in perceptual normalization and selective attention may contribute to the reduced speech understanding that is often reported for older adults.     

Perception of /r/ and /l/ in a stop cluster: Evidence of cross-modal context effects.

Experiments were conducted investigating unimodal and cross-modal phonetic context effects on /r/ and /l/ identifications to test a hypothesis that context effects arise in early auditory speech processing. Experiment 1 demonstrated an influence of a preceding bilabial stop consonant on the acoustic realization of /r/ and /l/ produced within the stop clusters /ibri/ and /ibli/. In Experiment 2, members of an acoustic /iri/ to /ili/ continuum were paired with an acoustic /ibi/. These dichotic tokens were associated with an increase in "l" identification relative to the /iri/ to /ili/ continuum. In Experiment 3, the /iri/ to /ili/ tokens were dubbed onto a video of a talker saying /ibi/. This condition was associated with a reliable perceptual shift relative to an auditory-only condition in which the /iri/ to /ili/ tokens were presented by themselves, ruling out an account of these context effects as arising during early auditory processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of angiotensin II, endothelin-1, and nitric oxide in HgCl2-induced acute renal failure

Although multichannel compression systems are quickly becoming integral components of programmable hearing aids, research results have not consistently demonstrated their benefit over conventional amplification. The present study examined two confounding factors that may have contributed to this inconsistency in results: alteration of temporal information and audibility of speech cues. Recognition of linearly amplified and multichannel-compressed speech was measured for listeners with mild-to-severe sensorineural hearing loss and for a control group of listeners with normal hearing. In addition to the standard speech signal, which provided both temporal and spectral information, the listener's ability to use temporal information in a multichannel compressed signal was directly tested using a signal-correlated noise (SCN) stimulus. This stimulus consisted of a time-varying speech envelope modulating a two-channel noise carrier. It preserved temporal cues but provided minimal spectral information. For each stimulus condition, short-term level measurements were used to determine the range of audible speech. Multichannel compression improved speech recognition under conditions where superior audibility was provided by the two-channel compression system over linear amplification. When audibility of both linearly amplified and multichannel-compressed speech was maximized, the multichannel compression had no significant effect on speech recognition score for speech containing both temporal and spectral cues. However, results for the SCN stimuli show that more extreme amounts of multichannel compression can reduce use of temporal information.     

The role of talker-specific information in word segmentation by infants.

Infants' representations of the sound patterns of words were explored by examining the effects of talker variability on the recognition of words in fluent speech. Infants were familiarized with isolated words (e.g., cup and dog) from 1 talker and then heard 4 passages produced by another talker, 2 of which included the familiarized words. At 7.5 months of age, infants attended longer to passages with the familiar words for materials produced by 2 female talkers or 2 male talkers but not for materials by a male and a female talker. These findings suggest a strong role for talker-voice similarity in infants' ability to generalize word tokens. By 10.5 months, infants could generalize different instances of the same word across talkers of the opposite sex. One implication of the present results is that infants' initial representations of the sound structure of words not only include phonetic information but also indexical properties relating to the vocal characteristics of particular talkers. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acquired transplant tolerance

For many people with profound hearing loss conventional hearing aids give only little support in speechreading. This study aims at optimizing the presentation of speech signals in the severely reduced dynamic range of the profoundly hearing impaired by means of multichannel compression and multichannel amplification. The speech signal in each of six 1-octave channels (125-4000 Hz) was compressed instantaneously, using compression ratios of 1, 2, 3, or 5, and a compression threshold of 35 dB below peak level. A total of eight conditions were composed in which the compression ratio varied per channel. Sentences were presented audio-visually to 16 profoundly hearing-impaired subjects and syllable intelligibility was measured. Results show that all auditory signals are valuable supplements to speechreading. No clear overall preference is found for any of the compression conditions, but relatively high compression ratios (> 3-5) have a significantly detrimental effect. Inspection of the individual results reveals that compression may be beneficial for one subject.     

Influence of interresponse time reinforcement on signalled-reward effect.

Examined the conditions under which presenting a signal for reinforcement decreases or increases the rate of leverpressing in rats. Response rate on a variable-interval (VI) schedule of reinforcement was decreased by a brief signal for reinforcement. In Experiment 1, requiring 1 short IRT to occur on completion of the VI requirement attenuated this response decrement. Requiring three responses to be emitted within a minimum amount of time at the end of the VI resulted in the reinforcement signal's enhancement of response rates. Experiment 2 replicated this increase in responding and showed that the reinforcement signal attenuated response rates on a simple VI schedule that yielded the same overall rate of reinforcement. In Experiment 3, the reinforcement signal enhanced response rates when 3 responses were required at the end of a VI schedule, but the signal attenuated response rates when the 3 responses could occur at any time in relation to the VI. These results suggest that the pattern of responding emitted immediately prior to reinforcement is a critical factor in determining the effect of reinforcement signal on response rate. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Error biases in inner and overt speech: Evidence from tongue twisters.

To compare the properties of inner and overt speech, Oppenheim and Dell (2008) counted participants' self-reported speech errors when reciting tongue twisters either overtly or silently and found a bias toward substituting phonemes that resulted in words in both conditions, but a bias toward substituting similar phonemes only when speech was overt. Here, we report 3 experiments revisiting their conclusion that inner speech remains underspecified at the subphonemic level, which they simulated within an activation-feedback framework. In 2 experiments, participants recited tongue twisters that could result in the errorful substitutions of similar or dissimilar phonemes to form real words or nonwords. Both experiments included an auditory masking condition, to gauge the possible impact of loss of auditory feedback on the accuracy of self-reporting of speech errors. In Experiment 1, the stimuli were composed entirely from real words, whereas, in Experiment 2, half the tokens used were nonwords. Although masking did not have any effects, participants were more likely to report substitutions of similar phonemes in both experiments, in inner as well as overt speech. This pattern of results was confirmed in a 3rd experiment using the real-word materials from Oppenheim and Dell (in press). In addition to these findings, a lexical bias effect found in Experiments 1 and 3 disappeared in Experiment 2. Our findings support a view in which plans for inner speech are indeed specified at the feature level, even when there is no intention to articulate words overtly, and in which editing of the plan for errors is implicated. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Atomized Spray Quenching as an Alternative Quenching Method for Defined Adjustment of Heat Transfer

In Atomized Spray Quenching, water is atomized to a fine spray by compressed air and sprayed onto the hot metallic surface. On the surface, the single drops partially evaporate. Afterwards they are taken away by the superposed airflow. Thus a water film cannot form. By quenching one edge, it is shown that an undefined water film collapses at the edges and corners; roughness, as known from Water Spray Quenching, does not occur. In this way a defined adjustment of heat transfer including quality improvement is possible. The influence of impingement density, spray characteristics, drop velocity, drop diameter and surface temperature on heat transfer was investigated. The heat transfer was measured with infrared thermography. The spray characteristics were measured with a combination of 2D‐Phase‐Doppler‐Anemometer and Patternator. Heat transfer coefficients up to 3000 W/(m² K) were measured.     

Perceptual learning of noise vocoded words: Effects of feedback and lexicality.

Speech comprehension is resistant to acoustic distortion in the input, reflecting listeners' ability to adjust perceptual processes to match the speech input. This adjustment is reflected in improved comprehension of distorted speech with experience. For noise vocoding, a manipulation that removes spectral detail from speech, listeners' word report showed a significantly greater improvement over trials for listeners that heard clear speech presentations before rather than after hearing distorted speech (clear-then-distorted compared with distorted-then-clear feedback, in Experiment 1). This perceptual learning generalized to untrained words suggesting a sublexical locus for learning and was equivalent for word and nonword training stimuli (Experiment 2). These findings point to the crucial involvement of phonological short-term memory and top-down processes in the perceptual learning of noise-vocoded speech. Similar processes may facilitate comprehension of speech in an unfamiliar accent or following cochlear implantation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Auditory-phonetic projection and lexical structure in the recognition of sine-wave words.

Speech remains intelligible despite the elimination of canonical acoustic correlates of phonemes from the spectrum. A portion of this perceptual flexibility can be attributed to modulation sensitivity in the auditory-to-phonetic projection, although signal-independent properties of lexical neighborhoods also affect intelligibility in utterances composed of words. Three tests were conducted to estimate the effects of exposure to natural and sine-wave samples of speech in this kind of perceptual versatility. First, sine-wave versions of the easy and hard word sets were created, modeled on the speech samples of a single talker. The performance difference in recognition of easy and hard words was used to index the perceptual reliance on signal-independent properties of lexical contrasts. Second, several kinds of exposure produced familiarity with an aspect of sine-wave speech: (a) sine-wave sentences modeled on the same talker; (b) sine-wave sentences modeled on a different talker, to create familiarity with a sine-wave carrier; and (c) natural sentences spoken by the same talker, to create familiarity with the idiolect expressed in the sine-wave words. Recognition performance with both easy and hard sine-wave words improved after exposure only to sine-wave sentences modeled on the same talker. Third, a control test showed that signal-independent uncertainty is a plausible cause of differences in recognition of easy and hard sine-wave words. The conditions of beneficial exposure reveal the specificity of attention underlying versatility in speech perception. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

热压缩形变不均匀性的影响因素及取样方法的研究

 采用有限元方法对热压缩物理模拟过程进行了模拟,分析了接触静摩擦系数、形变量、应变速率对热压缩方向应变及应变速率均匀性的影响,对不同取样位置及分析方向的形变均匀性进行了分析,并观察相对应的原奥氏体晶粒,进行验证。结果表明,试样热压缩方向的应变及应变速率由心部向端部逐步减小,距试样中心1/4位置处最接近设定的应变及应变速率;接触静摩擦系数对试样热压缩方向形变不均匀性影响显著,形变量、应变速率对形变不均匀性的影响较小;推荐自热压方向1/4位置处取样,该处应变及应变速率基本符合设定条件,且形变均匀性最好。     

Development and evaluation of a procedure for fitting multi-channel compression hearing aids

Hearing aids with multi-channel compression are often fitted on the basis of loudness scaling data obtained using narrow bands of noise or tones. Here, we report the development and evaluation of an alternative fitting procedure based on the use of speech signals. The parameters of the hearing aid (the gains in each channel for high and low input levels) are adjusted adaptively under computer control on the basis of the listener's responses. The goal is that speech at 85 dB SPL should be judged as 'loud', speech at 60 dB SPL should be judged as 'quiet', and speech at both levels should be judged as 'neither tinny nor boomy'. The procedure was evaluated using a two-channel compression hearing aid, the remote control of which allowed two programs to be stored. One program was based on our fitting procedure. The other was either based on the manufacturer's recommended full fitting procedure (which included loudness scaling with bands of noise), or was based on the audiogram alone, using the manufacturer's algorithm. After an acclimatization period of at least two weeks, subjects were then asked to fill in a questionnaire about their experiences with the two programs in different listening situations. The results generally indicated a preference for the program based on our adaptive fitting procedure. We also conducted laboratory measurements of speech intelligibility, in quiet and in a background of a single competing talker. These showed no clear difference between programs, although scores overall were very high. We conclude that our adaptive procedure gives very satisfactory results in everyday life. Parameter values giving good comfort also give good intelligibility. The procedure typically takes between five and 10 minutes per ear, which is quicker than most loudness scaling procedures.     

Perceiving the sex and identity of a talker without natural vocal timbre

The personal attributes of a talker perceived via acoustic properties of speech are commonly considered to be an extralinguistic message of an utterance. Accordingly, accounts of the perception of talker attributes have emphasized a causal role of aspects of the fundamental frequency and coarse-grain acoustic spectra distinct from the detailed acoustic correlates of phonemes. In testing this view, in four experiments, we estimated the ability of listeners to ascertain the sex or the identity of 5 male and 5 female talkers from sinusoidal replicas of natural utterances, which lack fundamental frequency and natural vocal spectra. Given such radically reduced signals, listeners appeared to identify a talker's sex according to the central spectral tendencies of the sinusoidal constituents. Under acoustic conditions that prevented listeners from determining the sex of a talker, individual identification from sinewave signals was often successful. These results reveal that the perception of a talker's sex and identity are not contingent and that fine-grain aspects of a talker's phonetic production can elicit individual identification under conditions that block the perception of voice quality.     

Learning to recognize talkers from natural, sinewave, and reversed speech samples.

In 5 experiments, the authors investigated how listeners learn to recognize unfamiliar talkers and how experience with specific utterances generalizes to novel instances. Listeners were trained over several days to identify 10 talkers from natural, sinewave, or reversed speech sentences. The sinewave signals preserved phonetic and some suprasegmental properties while eliminating natural vocal quality. In contrast, the reversed speech signals preserved vocal quality while distorting temporally based phonetic properties. The training results indicate that listeners learned to identify talkers even from acoustic signals lacking natural vocal quality. Generalization performance varied across the different signals and depended on the salience of phonetic information. The results suggest similarities in the phonetic attributes underlying talker recognition and phonetic perception. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Examining the Time Course of Indexical Specificity Effects in Spoken Word Recognition.

Variability in talker identity and speaking rate, commonly referred to as indexical variation, has demonstrable effects on the speed and accuracy of spoken word recognition. The present study examines the time course of indexical specificity effects to evaluate the hypothesis that such effects occur relatively late in the perceptual processing of spoken words. In 3 long-term repetition priming experiments, the authors examined reaction times to targets that were primed by stimuli that matched or mismatched on the indexical variable of interest (either talker identity or speaking rate). Each experiment was designed to manipulate the speed with which participants processed the stimuli. The results demonstrate that indexical variability affects participants' perception of spoken words only when processing is relatively slow and effortful. (PsycINFO Database Record (c) 2010 APA, all rights reserved)