Intelligibility of frequency-lowered speech produced by a channel vocoder

Frequency lowering is a form of signal processing designed to match speech to the residual auditory capacity of a listener with a high frequency hearing loss. A vocoder-based frequency-lowering system similar to one studied by Lippmann was evaluated in the present study. In this system, speech levels in high frequency bands modulated one-third-octave bands of noise at low frequencies, which were then added to unprocessed speech. Results obtained with this system indicated, in agreement with Lippmann, that processing improved the recognition of stop, fricative, and affricate consonants when the listening bandwidth was restricted to 800 Hz. However, results also showed that processing degraded the perception of nasals and semivowels, consonants not included in Lippmann's study. Based on these results, the frequency-lowering system was modified so as to suppress the processing whenever low frequency components dominated the input signal. High and low frequency energies of an input signal were measured continuously in the modified system, and the decision to process or to leave the signal unaltered was based on their relative levels. Results indicated that the modified system maintained the processing advantage for stops, fricatives, and affricates without degrading the perception of nasals and semi-vowels. The results of the present study also indicated that training is an important consideration when evaluating frequency-lowering systems.     

Recognition of multiply degraded speech by young and elderly listeners

This study investigated the hypothesis that age effects exert an increased influence on speech recognition performance as the number of acoustic degradations of the speech signal increases. Four groups participated: young listeners with normal hearing, elderly listeners with normal hearing, young listeners with hearing loss, and elderly listeners with hearing loss. Recognition was assessed for sentence materials degraded by noise, reverberation, or time compression, either in isolation or in binary combinations. Performance scores were converted to an equivalent signal-to-noise ratio index to facilitate direct comparison of the effects of different forms of stimulus degradation. Age effects were observed primarily in multiple degradation conditions featuring time compression of the stimuli. These results are discussed in terms of a postulated change in functional signal-to-noise ratio with increasing age.     

Distraction by competing speech in young and older adult listeners.

In 2 experiments, young and older adults heard target speech presented in quiet or with a competing speaker in the background. The distractor consisted either of meaningful speech or nonmeaningful speech composed of randomly ordered word strings (Experiment 1) or speech in an unfamiliar language (Experiment 2). Tests of recall for the target speech showed that older adults, but not younger adults, were impaired more by meaningful distractors than by nonmeaningful distracters, However, on a surprise recognition test, young adults were more likely than older adults to recognize meaningful distractor items. These results suggest that reduced efficiency in attentional control is an important factor in older adults' difficulty in recalling target speech in the presence of a background of competing speech. (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.     

Classification of domestic cat (Felis catus) vocalizations by naive and experienced human listeners.

To test for possible functional referentiality in a common domestic cat (Felis catus) vocalization, the authors conducted 2 experiments to examine whether human participants could classify meow sounds recorded from 12 different cats in 5 behavioral contexts. In Experiment 1, participants heard single calls, whereas in Experiment 2, bouts of calls were presented. In both cases, classification accuracy was significantly above chance, but modestly so. Accuracy for bouts exceeded that for single calls. Overall, participants performed better in classifying individual calls if they had lived with, interacted with, and had a general affinity for cats. These results provide little evidence of referentiality, suggesting instead that meows are nonspecific, somewhat negatively toned stimuli that attract attention from humans. With experience, human listeners can become more proficient at inferring positive-affect states from cat meows. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Factors governing speech reception benefits of adaptive linear filtering for listeners with sensorineural hearing loss

Adaptive linear filtering can improve effective speech-to-noise ratios by attenuating spectral regions with intense noise components to reduce the noise's spread of masking onto speech in neighboring regions. This mechanism was examined in static listening conditions for seven individuals with sensorineural hearing loss. Subjects were presented with nonsense syllables in an intense octave-band noise centered on 0.5, 1, or 2 kHz. The nonsense syllables were amplified to maximize. the articulation index; the noises were the same for all subjects. The processing consisted of applying frequency-selective attenuation to the speech-plus-noise with the goal of attenuating the frequency region containing the noise by various amounts. Consonant recognition scores and noise masking patterns were collected in all listening conditions. When compared with masking patterns obtained from normal-hearing subjects, all hearing-impaired subjects had higher masked thresholds at frequencies below, within, and above the masker band except for one subject who demonstrated additional masking above the masker only. Frequency-selective attenuation resulted in both increases and decreases in consonant recognition scores. Increases were associated with a release from upward spread of masking. Decreases were associated with applying too much attenuation such that speech energy within the masker band that was audible before processing was partially below threshold after processing. Fletcher's [Speech and Hearing in Communication (Van Nostrand, New York, 1953)] version of articulation theory (without modification) accounted for individual subject differences within the range of variability associated with the consonant recognition test in almost every instance. Hence, primary factors influencing speech reception benefits are characterized by articulation theory. Fletcher's theory appears well-suited to guide the design of control algorithms that will maximize speech recognition for individual listeners.     

Effects of contralateral speech competition on auditory event-related potentials recorded from elderly listeners: brain map study

Topographic brain mapping was used to investigate the ability of young and elderly female listeners to attend to tones at one ear in the presence of speech competition at the opposite ear. An oddball stimulus presentation paradigm was used to record the N1, P2, and P300 components of the late auditory evoked potential from 19 scalp locations. With speech competition, elderly listeners exhibited significantly larger reductions in N1 amplitude than did young listeners. This suggests that N1 may provide an electrophysiologic index of age-related breakdowns in processing sounds in the presence of background competition. An unexpected difference was also found between young and elderly listeners in P300 scalp topography. While the young listeners' P300 response was centered at midline for both left and right ear stimulation, the elderly participants had P300 maxima centered in the parietal area of the hemisphere located contralateral to the test ear. This suggests that some of the functional properties (e.g., timing, strength, orientation) of the P300 neural generators may change with age or, alternatively, that different generators may be operative in elderly listeners.     

FO processing and the separation of competing speech signals by listeners with normal hearing and with hearing loss

Normal-hearing and hearing-impaired listeners were tested to determine F0 difference limens for synthetic tokens of 5 steady-state vowels. The same stimuli were then used in a concurrent-vowel labeling task with the F0 difference between concurrent vowels ranging between 0 and 4 semitones. Finally, speech recognition was tested for synthetic sentences in the presence of a competing synthetic voice with the same, a higher, or a lower F0. Normal-hearing listeners and hearing-impaired listeners with small F0-discrimination (deltaF0) thresholds showed improvements in vowel labeling when there were differences in F0 between vowels on the concurrent-vowel task. Impaired listeners with high deltaF0 thresholds did not benefit from F0 differences between vowels. At the group level, normal-hearing listeners benefited more than hearing-impaired listeners from F0 differences between competing signals on both the concurrent-vowel and sentence tasks. However, for individual listeners, deltaF0 thresholds and improvements in concurrent-vowel labeling based on F0 differences were only weakly associated with F0-based improvements in performance on the sentence task. For both the concurrent-vowel and sentence tasks, there was evidence that the ability to benefit from F0 differences between competing signals decreases with age.     

Audiological correlates of speech understanding deficits in elderly listeners with mild-to-moderate hearing loss. II. Correlation analysis

OBJECTIVE: The study was conducted to determine the relationship between measures of auditory performance in elderly individuals. Specifically, its goal was to uncover a set of measures correlated with the set of measures of speech understanding under specific conditions of interference to gain a better understanding of decline of the "cocktail party effect" in aging. DESIGN: Audiological status and auditory performance of a group of elderly (60- to 81-yr-old) individuals were determined through a test battery. When present, the hearing loss of elderly subjects was symmetrical in the two ears and, at most, moderate. The battery included tests of speech intelligibility on the word and sentence levels, with and without the presence of interfering speech. In addition pure-tone and speech reception thresholds, perception of spectrally or temporally distorted speech and auditory resolution of frequency, time, and space were tested. Two tests received special consideration: the Speech Perception In Noise Test and the Modified Rhyme Reverberation Test. RESULTS: Results indicated that, despite the nearly normal hearing levels that characterized much of the subject group, auditory sensitivity measures showed persistent correlation to all other measures, with the exception of auditory resolution regarding frequency, time, and space. As a set, sensitivity measures accounted for more than 85% of the variance. When auditory sensitivity was controlled for, other factors underlying speech processing in the presence of interfering stimuli were uncovered, factors most likely related to the ability to perceptually segregate one speech signal from another. CONCLUSIONS: The findings suggest that, to determine the relationship between audiological/auditory test results of an elderly population, it is important to remove the effects of hearing loss through appropriate statistical methods.     

Development of private speech among low-income Appalachian children.

Observed the occurrence of 9 subtypes of private speech (e.g., self-guidance and expression of affect) among 36 low-income 5–10 yr old Appalachian children in the school environment. Narratives of Ss' behavior were recorded and coded. Findings support L. Vygotsky's (1962) viewpoint in that most private speech appeared to serve a cognitively self-guiding function. Subtypes showed developmental trends predicted by Vygotsky's theory, resembled those found by L. Kohlberg et al (1968), and showed generally positive relationships with social speech. Private speech increased under conditions of cognitively demanding tasks and adult absence. The suggestion by Kohlberg claiming that private speech is functionally unitary and that the subtypes emerge in a hierarchically related sequence was not supported. Ss were slower in rate but not different in form of development as compared with previously studied middle-class children. Boys developed more slowly than did girls, a finding related to Appalachian cultural sex roles. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Repair of inflammatory tracheoesophageal fistula

Benign acquired tracheoesophageal fistula is uncommon. Erosin of the membranous wall of the trachea and the anterior esophageal wall by the high-pressure cuff on a tracheostomy tube, often against the anvil of a nasogastric tube, may produce such fistulas. Techniques for closure have included patching the tracheal defect with muscle and, often, multiple staged procedures, planned or unplanned. Since any cuff lesion severe enough to cause a fistula necessarily damages the trachea circumferentially at the same level, definitive correction must include circumferential tracheal resection as well as closure of the fitstula. Five patients with tracheoesophageal fistula due to cuff perforation had repair by such a single-stage procedure. Through an anterior approach the involved trachea was resected, primary anastomosis was done, and the esophagus was closed in layers. In 3 of these 5 patients muscle was interposed for added security. One patient had undergone a prior attempt at repair elsewhere. One required a second resection of trachea for subsequent stomal stenosis. Repair in 2 additional patients with fistulas of complex origin related to direct trauma, sepsis, and foreign body involved adaptation of the basic technique to the special problem; 1 of these procedures was necessarily staged. Results in all 7 patients have been good.     

Asymmetric relationships among perceptions of facial identity, emotion, and facial speech

Effects of variation in an irrelevant stimulus dimension on judgments of faces with respect to a relevant dimension were investigated. Dimensions were identity, emotional expression, and facial speech. The irrelevant dimension was correlated with, constant, or orthogonal to the relevant one. Reaction times (RTs) were predicted to increase over these conditions to the extent that the relevant dimension could not be processed independently of the irrelevant one. RTs for identity judgments were independent of variation in expression or facial speech, but RTs for expression and facial speech judgments were influenced by identity variation. Facial speech perception was affected by identity even when variation in the mouth region was eliminated. Moreover, observers could judge speech faster for personally familiar faces than for unfamiliar faces. The results suggest asymmetric dependencies between different components of face perception. Identity is perceived independently of, but may exert an influence on, expression and facial speech analysis.     

Antenatal diagnosis of esophageal atresia with tracheoesophageal fistula

We have studied the antibody response to hepatitis B vaccine in 42 hemodialysis patients; 8 of them were diagnosed as having HCV infection before vaccination. Hemodialysis patients received four doses of recombinant HB vaccine (Engerix-B, SKB, 40 micrograms per dose). Seroconversion occurred in 71.4% of all hemodialysis patients; in 79.4% of HCV-negative and in 37.5% of HCV-positive patients. Effective immunity (anti-HBs titer higher than 100 m IU/ml) was observed in 12.5% of HCV positive and in 35.3% of HCV-negative patients. We conclude that HCV infection may modify or postpone the response to hepatitis B vaccine.     

Surgical closure of persisting failed tracheoesophageal voice fistula

Tracheoesophageal puncture (TEP) is a highly successful procedure for voice restoration. Occasionally, however, patients fail to achieve satisfactory voice or develop salivary leakage through the fistula into the trachea. Closure of the TEP is then necessary. In most cases, spontaneous closure occurs once the prosthesis has been removed. When the fistula does not close spontaneously, surgical closure is indicated to prevent aspiration and pulmonary complications. We describe a three-layer technique that employs interposition of dermal graft. The technique was used on 14 patients over a 7-year period. Most patients received irradiation to the neck. Complete closure was achieved in 13 of 14 cases; 1 patient developed partial breakdown of the closure. Our technique is relatively easy to perform and has a high success rate (92%). Irradiation did not adversely affect the closure rate.     

Process and strategy in memory for speech among younger and older adults.

Younger and older adults listened to and immediately recalled short passages of speech that varied in the rate of presentation and in the degree of linguistic and prosodic cuing. Although older adults showed a differential decrease in recall performance as a function of increasing speech rate, age differences in recall were reduced by the presence of linguistic and prosodic cues. Under conditions of optimum linguistic redundancy, older adults were also found to add more words and to make more meaning-producing reconstructions in recall. Differences in overall performance are accounted for in terms of age-related changes in working memory processing and strategy utilization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The recirculation of naive and memory lymphocytes

It has been clearly shown that continuous recirculation of lymphocytes is crucial for the development of primary immune responses and that naive CD4 cells are distinguished from memory CD4 cells by differences in expression of several adhesion molecules. These findings suggest that changes in migratory behavior accompany the naive to memory cell transition. This area is first reviewed and then to evaluate this hypothesis, we compare the tissue distributions of highly purified naive and memory CD4 cells after transfer to syngeneic recipients. Naive cells which express high levels of L-selectin, and low levels of alpha 4 and beta 2 integrins, and CD44 localized in secondary lymphoid organs and were detectable in these tissues and in the blood for several weeks after transfer. Memory cells, which have a reciprocal phenotype, showed a markedly different distribution, particularly with respect to tissues where entry is controlled through high endothelial venules.     

Young children's understanding of interpretive diversity between different-age listeners.

Tested children's understanding of interpretive diversity by assessing their attributions of knowledge to a mother and a preverbal baby, who both had access to an informative verbal message. In Exp 1, most children between ages 4 and 8 yrs overattributed knowledge to the preverbal baby after an informative message. Exps 1a and 1b demonstrated that overattributions were not due to conflating the speaker's intent to inform with the informativeness of the message, nor were they due to overestimating babies' limited knowledge. In Exp 2, 6- and 8-yr-olds acknowledged interpretive differences between the baby and adult listener if the message was not obviously informative. It is concluded that children do not readily view individual differences as related to interpretive differences, especially in the absence of cues inherent to a message that might suggest that the message has multiple interpretations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Human listeners provide insights into echo features used by dolphins (Tursiops truncatus) to discriminate among objects.

Echolocating bottlenose dolphins (Tursiops truncatus) discriminate between objects on the basis of the echoes reflected by the objects. However, it is not clear which echo features are important for object discrimination. To gain insight into the salient features, the authors had a dolphin perform a match-to-sample task and then presented human listeners with echoes from the same objects used in the dolphin's task. In 2 experiments, human listeners performed as well or better than the dolphin at discriminating objects, and they reported the salient acoustic cues. The error patterns of the humans and the dolphin were compared to determine which acoustic features were likely to have been used by the dolphin. The results indicate that the dolphin did not appear to use overall echo amplitude, but that it attended to the pattern of changes in the echoes across different object orientations. Human listeners can quickly identify salient combinations of echo features that permit object discrimination, which can be used to generate hypotheses that can be tested using dolphins as subjects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Test-retest reliability of high-frequency thresholds at bedside with sensorineural hearing-impaired listeners

Previous investigations have established the reliability of high-frequency thresholds performed in a sound suite using headphones. In addition, test-retest reliability of high-frequency thresholds in adults with normal hearing in a hospital room versus a sound-treated booth has also been established. The current study evaluated the test-retest reliability of thresholds in the 8000- to 18000-Hz range in 15 hearing-impaired adults (26 ears) with varying degrees of sensorineural hearing loss. A high-frequency audiometer and supra-aural earphones were used to measure thresholds in a typical hospital room. Results revealed no significant difference between repeated threshold measures. This study represents the third phase of an ongoing project to develop reliable bedside monitoring of patients undergoing ototoxic medical treatment.     

Production of intoxication states by actors: perception by lay listeners

The effects of ingesting ethanol have been shown to be somewhat variable in humans; there appear to be but few universals. Yet, questions about intoxication often are asked by law enforcement personnel (especially relative to DUI), clinicians and various individuals in social settings. A key question: Is it possible to determine if a person is intoxicated by observing them in some manner? A closely associated one: Can speech be used for that purpose? Two of the many issues related to the second of these questions involve the possibility that (1) speakers, especially actors, can effectively mimic the speech of intoxicated individuals, and (2) they may be able to volitionally reduce any speech degradation which results from intoxication. The approach used to test these two questions tasked auditors to determine if these simulations were possible. To this end, young, healthy actors chosen on the basis of a large number of selection criteria were asked to produce several types of controlled utterances (1) during a learning phase, (2) when sober, (3) at three simulated levels of intoxication (mildly, legally and severely drunk), (4) during actual, and parallel, levels of intoxication, and (5) at the highest intoxication level attained but when attempting to sound completely sober. Two aural-perceptual studies were conducted; both involved counterbalanced ABX procedures where each subject was paired with him/herself. Listeners were normally hearing university students drawn from undergraduate phonetics and linguistics courses. In the first study, they rated the actors as being more intoxicated--when they actually were sober but simulating drunkenness--88% more often than when they actually were intoxicated. In the second study, they were judged as sounding less inebriated when attempting to sound sober (than they actually were) 61% of the time. These relationships would appear to impact a number of situations; one of special importance would be the detection of intoxication in motorists.