Investigating the Utility of a Compact Loudspeaker Array for Audiometric Testing.

PURPOSE: This project addressed the uses of a loudspeaker array for audiometric measurements. It sought to evaluate a prototype compact array in terms of the reliability of test results across sound booths. METHOD: A seven-loudspeaker array was developed to deliver sounds from -60° to +60° on an arc with a radius of 0.5 m. The system was equipped with a head position sensing system to maintain the listener's head near the optimal test position. Three array systems were distributed to each of the two test sites for within-subject assessments of booth equivalence on tests of sound localization, speech reception in noise, and threshold detection. A total of 36 subjects participated, 18 at each test site. RESULTS: Results showed excellent interbooth consistency on tests of sound localization using speech and noise signals, including conditions in which one or both ears were covered with a muff. Booth consistency was also excellent on sound field threshold measurements for detecting quasi-diffuse noise bands. Nonequivalence was observed in some cases of speech-in-noise tests, particularly with a small one-person booth. Acoustic analyses of in situ loudspeaker responses indicated that some of the nonequivalent comparisons on speech-in-noise tests could be traced to the effects of reflections. CONCLUSIONS: Overall, the results demonstrate the utility and reliability of a compact array for the assessment of localization ability, speech reception in noise, and sound field thresholds. However, the results indicate that researchers and clinicians should be aware of the reflection effects that can influence the results of sound field tests in which signal and noise levels from separate loudspeakers are critical.

An Exploratory Study of Walking, Listening, and Remembering in Younger and Middle-Aged Adults.

PURPOSE: The purpose of this study was to assess how needing to listen and remember information while walking affects speech perception, memory task performance, and gait in younger and middle-aged adults. METHOD: Four gait parameters (stride duration, step variability, whole-body center of mass acceleration, and mediolateral head acceleration) were measured when younger and middle-aged participants stood or walked on a treadmill while they simultaneously completed a speech-on-speech perception task and a preload memory task, singly and in combination. RESULTS: Speech perception was significantly poorer for middle-aged than for younger participants. Performance on the speech perception measure did not differ significantly between walking and standing for either group of participants, but the additional cognitive load of the memory task reduced performance on the speech perception task. Memory task performance was significantly poorer when combined with the speech perception task than when measured in isolation for both participant groups, but no further declines were noted when participants were also walking. Mediolateral head acceleration, which has been linked to loss of balance, was significantly greater during multitask trials, as compared to when participants were only walking without being required to listen or remember. Post hoc analysis showed that dual- and multitask influences on mediolateral head acceleration were more prominent for middle-aged than for younger participants. Stride duration was longer in the multitask condition than when participants were only walking. CONCLUSIONS: Results of this exploratory study indicate that gait may be impacted when individuals (both younger and middle-aged) are listening and remembering while walking. Data also substantiate prior findings of early age-related declines in the perception of speech in the presence of understandable speech maskers.

Spatial release from informational masking enhances the early cortical representation of speech sounds.

Introduction: Spatial separation between competing speech streams reduces their confusion (informational masking), improving speech processing under challenging listening conditions. The precise stages of auditory processing involved in this benefit are not fully understood. This study used event-related potentials to examine the processing of target speech under conditions of informational masking and its spatial release. Methods: Participants detected noise-vocoded target speech presented with two-talker noise-vocoded masking speech. In separate conditions, the same set of targets were spatially co-located with maskers to produce informational masking and spatially separated from maskers using a perceptual manipulation to release the informational masking. Results: An increase in N1 and P2 amplitude, consistent with cortical auditory evoked potentials, and a later sustained positivity (P300) were observed in response to target onsets only under conditions supporting release from informational masking. At target intensities above masking threshold in both spatial conditions, N1 and P2 latencies were shorter when targets and maskers were perceptually separated. Discussion: These results indicate that spatial release from informational masking benefits speech representation beginning in the early stages of auditory perception. Additionally, these results suggest that the auditory evoked potential itself may be heavily dependent upon how information is perceptually organized rather than physically organized.

Early aging and postural control while listening and responding.

It is not unusual for communication to take place while people are involved in another activity. This paper describes a study that measures the impact of listening while also completing an active postural control task. The focus was on whether the combination of listening and balancing was more detrimental to middle-aged adults than it was to younger adults as age-related changes in both hearing and postural control can occur within this age range. Speech understanding in the presence of noise and speech maskers was measured when participants (n = 15/group) were simply standing still, as well as when they were asked to complete a balancing-with-feedback postural control task, requiring different levels of effort. Performance on the postural control task also was measured in isolation. Results indicated that dual-task costs for postural control were larger when the masker was speech (vs noise) for the middle-aged group but not for the younger group. Dual-task costs in postural control increased with degree of high-frequency hearing loss even when age was controlled. Overall, results suggest that postural control in middle-aged adults can be compromised when individuals are communicating in challenging environments, perhaps reflecting an increased need for cognitive resources to successfully understand messages.

Postural Control While Listening in Younger and Middle-Aged Adults.

OBJECTIVES: The motivation for this research is to determine whether a listening-while-balancing task would be sensitive to quantifying listening effort in middle age. The premise behind this exploratory work is that a decrease in postural control would be demonstrated in challenging acoustic conditions, more so in middle-aged than in younger adults. DESIGN: A dual-task paradigm was employed with speech understanding as one task and postural control as the other. For the speech perception task, participants listened to and repeated back sentences in the presence of other sentences or steady-state noise. Targets and maskers were presented in both spatially-coincident and spatially-separated conditions. The postural control task required participants to stand on a force platform either in normal stance (with feet approximately shoulder-width apart) or in tandem stance (with one foot behind the other). Participants also rated their subjective listening effort at the end of each block of trials. RESULTS: Postural control was poorer for both groups of participants when the listening task was completed at a more adverse (vs. less adverse) signal-to-noise ratio. When participants were standing normally, postural control in dual-task conditions was negatively associated with degree of high-frequency hearing loss, with individuals who had higher pure-tone thresholds exhibiting poorer balance. Correlation analyses also indicated that reduced speech recognition ability was associated with poorer postural control in both single- and dual-task conditions. Middle-aged participants exhibited larger dual-task costs when the masker was speech, as compared to when it was noise. Individuals who reported expending greater effort on the listening task exhibited larger dual-task costs when in normal stance. CONCLUSIONS: Listening under challenging acoustic conditions can have a negative impact on postural control, more so in middle-aged than in younger adults. One explanation for this finding is that the increased effort required to successfully listen in adverse environments leaves fewer resources for maintaining balance, particularly as people age. These results provide preliminary support for using this type of ecologically-valid dual-task paradigm to quantify the costs associated with understanding speech in adverse acoustic environments.

Auditory Comprehension in School-Aged Children With Normal Hearing and With Unilateral Hearing Loss.

Purpose The purpose of this study was to measure auditory comprehension performance in school-aged children with unilateral hearing loss (UHL) and with normal hearing (NH) in quiet and in the presence of child-produced two-talker babble (TTB). Method Listeners were school-aged children (7-12 years) with permanent UHL (n = 25) or NH (n = 14). Comprehension of three short stories taken from the Test of Narrative Language (Gillam & Pearson, 2004) was measured in quiet and in the presence of TTB at two signal-to-noise ratios (SNRs): (a) +6 dB and (b) the individualized SNR required to achieve 50% sentence understanding in the presence of the same TTB masker in a prior study (Griffin, Poissant, & Freyman, 2019). Target/masker spatial configuration was 0°/±60° azimuth. Results As a group, subjects with UHL demonstrated auditory comprehension abilities in favorable listening environments (i.e., quiet, +6 dB SNR) that were statistically equivalent to the NH group. However, in the most challenging listening condition (individualized SNR), many subjects with UHL demonstrated poorer comprehension performance than their age-matched peers with NH. Comprehension abilities were not associated with degree of UHL, unaided speech intelligibility index at 65 dB SPL in the impaired ear, side of UHL, or sex. Conclusions As a group, children with UHL demonstrated deficits in auditory comprehension compared to age-matched peers with NH in challenging listening environments. Findings highlight the importance of ensuring good SNRs for children with UHL.

Speech-in-Noise and Quality-of-Life Measures in School-Aged Children With Normal Hearing and With Unilateral Hearing Loss.

OBJECTIVES: (1) Measure sentence recognition in co-located and spatially separated target and masker configurations in school-aged children with unilateral hearing loss (UHL) and with normal hearing (NH). (2) Compare self-reported hearing-related quality-of-life (QoL) scores in school-aged children with UHL and NH. DESIGN: Listeners were school-aged children (6 to 12 yrs) with permanent UHL (n = 41) or NH (n = 35) and adults with NH (n = 23). Sentence reception thresholds (SRTs) were measured using Hearing In Noise Test-Children sentences in quiet and in the presence of 2-talker child babble or a speech-shaped noise masker in target/masker spatial configurations: 0/0, 0/-60, 0/+60, or 0/±60 degrees azimuth. Maskers were presented at a fixed level of 55 dBA, while the level of the target sentences varied adaptively to estimate the SRT. Hearing-related QoL was measured using the Hearing Environments and Reflection on Quality of Life (HEAR-QL-26) questionnaire for child subjects. RESULTS: As a group, subjects with unaided UHL had higher (poorer) SRTs than age-matched peers with NH in all listening conditions. Effects of age, masker type, and spatial configuration of target and masker signals were found. Spatial release from masking was significantly reduced in conditions where the masker was directed toward UHL subjects' normal-hearing ear. Hearing-related QoL scores were significantly poorer in subjects with UHL compared to those with NH. Degree of UHL, as measured by four-frequency pure-tone average, was significantly correlated with SRTs only in the two conditions where the masker was directed towards subjects' normal-hearing ear, although the unaided Speech Intelligibility Index at 65 dB SPL was significantly correlated with SRTs in four conditions, some of which directed the masker to the impaired ear or both ears. Neither pure-tone average nor unaided Speech Intelligibility Index was correlated with QoL scores. CONCLUSIONS: As a group, school-aged children with UHL showed substantial reductions in masked speech perception and hearing-related QoL, irrespective of sex, laterality of hearing loss, and degree of hearing loss. While some children demonstrated normal or near-normal performance in certain listening conditions, a disproportionate number of thresholds fell in the poorest decile of the NH data. These findings add to the growing literature challenging the past assumption that one ear is "good enough."

How repetition influences speech understanding by younger, middle-aged and older adults.

OBJECTIVE: To examine benefit from immediate repetition of a masked speech message in younger, middle-aged and older adults. DESIGN: Participants listened to sentences in conditions where only the target message was repeated, and when both the target message and its accompanying masker (noise or speech) were repeated. In a follow-up experiment, the effect of repetition was evaluated using a square-wave modulated noise masker to compare benefit when listeners were exposed to the same glimpses of the target message during first and second presentation versus when the glimpses differed. STUDY SAMPLE: Younger, middle-aged and older adults (n = 16/group) for the main experiment; 15 younger adults for the follow-up experiment. RESULTS: Repetition benefit was larger when the target but not the masker was repeated for all groups. This was especially true for older adults, suggesting that these individuals may be more negatively affected when a background message is repeated. Data obtained using noise maskers suggest that it is slightly more beneficial when listeners hear different (versus identical) portions of speech between initial presentation and repetition. CONCLUSIONS: Although subtle age-related differences were found in some conditions, results confirm that repetition is an effective repair strategy for listeners spanning the adult age range.

Can monaural temporal masking explain the ongoing precedence effect?

The precedence effect for transient sounds has been proposed to be based primarily on monaural processes, manifested by asymmetric temporal masking. This study explored the potential for monaural explanations with longer ("ongoing") sounds exhibiting the precedence effect. Transient stimuli were single lead-lag noise burst pairs; ongoing stimuli were trains of 63 burst pairs. Unlike with transients, monaural masking data for ongoing sounds showed no advantage for the lead, and are inconsistent with asymmetric audibility as an explanation for ongoing precedence. This result, along with supplementary measurements of interaural time discrimination, suggests different explanations for transient and ongoing precedence.

The Effects of Musical Training on Speech Detection in the Presence of Informational and Energetic Masking.

Recent research has suggested that musicians have an advantage in some speech-in-noise paradigms, but not all. Whether musicians outperform nonmusicians on a given speech-in-noise task may well depend on the type of noise involved. To date, few groups have specifically studied the role that informational masking plays in the observation of a musician advantage. The current study investigated the effect of musicianship on listeners' ability to overcome informational versus energetic masking of speech. Monosyllabic words were presented in four conditions that created similar energetic masking but either high or low informational masking. Two of these conditions used noise-vocoded target and masking stimuli to determine whether the absence of natural fine structure and spectral variations influenced any musician advantage. Forty young normal-hearing listeners (20 musicians and 20 nonmusicians) completed the study. There was a significant overall effect of participant group collapsing across the four conditions; however, planned comparisons showed musicians' thresholds were only significantly better in the high informational masking natural speech condition, where the musician advantage was approximately 3 dB. These results add to the mounting evidence that informational masking plays a role in the presence and amount of musician benefit.

Strength of onset and ongoing cues in judgments of lateral position.

This study describes the contributions to auditory image position of an interaural time delay (ITD) cue at onset relative to subsequent ITDs during the ongoing part of a stimulus. Test stimuli were trains of 1-ms binaural noise bursts; lateral position was measured with a wideband acoustic pointer that subjects adjusted to match the intracranial position of test stimuli. In different conditions the ongoing part of the stimulus (the bursts following the first one) either had a consistent ITD (the same ITD on each ongoing burst), or had alternating leading and lagging components with ITDs that opposed one another. As duration of the ongoing part was increased from 4 to 250 ms, with the initial ITD fixed, lateral position changed from being dominated by the onset ITD to being dominated by the ongoing consistent or leading ITD. With alternating ongoing ITDs equal contributions from onset and ongoing parts were obtained at an ongoing duration of about 40 ms; with consistent ongoing ITDs equal contributions were obtained at about 15 ms. The results point up the increased dominance of onset cues when ongoing cues are ambiguous, as they often are in real-world settings.

The Effect of Aging and Priming on Same/Different Judgments Between Text and Partially Masked Speech.

OBJECTIVES: It is well known from previous research that when listeners are told what they are about to hear before a degraded or partially masked auditory signal is presented, the speech signal "pops out" of the background and becomes considerably more intelligible. The goal of this research was to explore whether this priming effect is as strong in older adults as in younger adults. DESIGN: Fifty-six adults-28 older and 28 younger-listened to "nonsense" sentences spoken by a female talker in the presence of a 2-talker speech masker (also female) or a fluctuating speech-like noise masker at 5 signal-to-noise ratios. Just before, or just after, the auditory signal was presented, a typed caption was displayed on a computer screen. The caption sentence was either identical to the auditory sentence or differed by one key word. The subjects' task was to decide whether the caption and auditory messages were the same or different. Discrimination performance was reported in d'. The strength of the pop-out perception was inferred from the improvement in performance that was expected from the caption-before order of presentation. A subset of 12 subjects from each group made confidence judgments as they gave their responses, and also completed several cognitive tests. RESULTS: Data showed a clear order effect for both subject groups and both maskers, with better same-different discrimination performance for the caption-before condition than the caption-after condition. However, for the two-talker masker, the younger adults obtained a larger and more consistent benefit from the caption-before order than the older adults across signal-to-noise ratios. Especially at the poorer signal-to-noise ratios, older subjects showed little evidence that they experienced the pop-out effect that is presumed to make the discrimination task easier. On average, older subjects also appeared to approach the task differently, being more reluctant than younger subjects to report that the captions and auditory sentences were the same. Correlation analyses indicated a significant negative association between age and priming benefit in the two-talker masker and nonsignificant associations between priming benefit in this masker and either high-frequency hearing loss or performance on the cognitive tasks. CONCLUSIONS: Previous studies have shown that older adults are at least as good, if not better, at exploiting context in speech recognition, as compared with younger adults. The current results are not in disagreement with those findings but suggest that, under some conditions, the automatic priming process that may contribute to benefits from context is not as strong in older as in younger adults.

Aging and the effect of target-masker alignment.

Similarity between target and competing speech messages plays a large role in how easy or difficult it is to understand messages of interest. Much research on informational masking has used highly aligned target and masking utterances that are very similar semantically and syntactically. However, listeners rarely encounter situations in real life where they must understand one sentence in the presence of another (or more than one) highly aligned, syntactically similar competing sentence(s). The purpose of the present study was to examine the effect of syntactic/semantic similarity of target and masking speech in different spatial conditions among younger, middle-aged, and older adults. The results of this experiment indicate that differences in speech recognition between older and younger participants were largest when the masker surrounded the target and was more similar to the target, especially at more adverse signal-to-noise ratios. Differences among listeners and the effect of similarity were much less robust, and all listeners were relatively resistant to masking, when maskers were located on one side of the target message. The present results suggest that previous studies using highly aligned stimuli may have overestimated age-related speech recognition problems.

Age equivalence in the benefit of repetition for speech understanding.

Although repetition is the most commonly used conversational repair strategy, little is known about its relative effectiveness among listeners spanning the adult age range. The purpose of this study was to identify differences in how younger, middle-aged, and older adults were able to use immediate repetition to improve speech recognition in the presence of different kinds of maskers. Results suggest that all groups received approximately the same amount of benefit from repetition. Repetition benefit was largest when the masker was fluctuating noise and smallest when it was competing speech.

Temporal effects in priming of masked and degraded speech.

When listeners know the content of the message they are about to hear, the clarity of distorted or partially masked speech increases dramatically. The current experiments investigated this priming phenomenon quantitatively using a same-different task where a typed caption and auditory message either matched exactly or differed by one key word. Four conditions were tested with groups of normal-hearing listeners: (a) natural speech presented in two-talker babble in a non-spatial configuration, (b) same as (a) but with the masker time reversed, (c) same as (a) but with target-masker spatial separation, and (d) vocoded sentences presented in speech-spectrum noise. The primary manipulation was the timing of the caption relative to the auditory message, which varied in 20 steps with a resolution of 200 ms. Across all four conditions, optimal performance was achieved when the initiation of the text preceded the acoustic speech signal by at least 400 ms, driven mostly by a low number of "different" responses to Same stimuli. Performance was slightly poorer with simultaneous delivery and much poorer when the auditory signal preceded the caption. Because priming may be used to facilitate perceptual learning, identifying optimal temporal conditions for priming could help determine the best conditions for auditory training.

Attention is critical for spatial auditory object formation.

The precedence effect provides a novel way to examine the role of attention in auditory object formation. When presented with two identical sounds from different locations separated by a short stimulus onset asynchrony (SOA), listeners report a single auditory object at the location of the lead sound. When the SOA is above the echo threshold, listeners report hearing two auditory objects with different locations. Event-related potential (ERP) studies have shown that the number of perceived auditory objects is reflected in an object-related negativity (ORN) 100-250 ms after onset and in a posterior late positivity (LP) 300-500 ms after onset. In the present study, we tested whether these ERP effects are modulated by attention by presenting lead/lag click pairs at and around listeners' echo thresholds, while in separate blocks the listeners (1) attended to the sounds and reported whether the lag sound was a separate source, and (2) performed a two-back visual task. When attention was directed away from the sounds, neither the ORN nor the LP observed in the attend condition was evident. Instead, unattended click pairs above the echo threshold elicited an anterior positivity 250-450 ms after onset. However, an effect resembling an ORN was found in comparing the ERPs elicited by unattended click pairs with SOAs below the attended echo threshold, indicating that the echo threshold may have been lowered when attention was directed away from the sounds. These results suggest that attention modulates early perceptual processes that are critical for auditory object formation.

Stimulus and listener factors affecting age-related changes in competing speech perception.

The purpose of this study was to examine associations among hearing thresholds, cognitive ability, and speech understanding in adverse listening conditions within and between groups of younger, middle-aged, and older adults. Participants repeated back sentences played in the presence of several types of maskers (syntactically similar and syntactically different competing speech from one or two other talkers, and steady-state speech-shaped noise). They also completed tests of auditory short-term/working memory, processing speed, and inhibitory ability. Results showed that group differences in accuracy of word identification and in error patterns differed depending upon the number of masking voices; specifically, older and middle-aged individuals had particular difficulty, relative to younger subjects, in the presence of a single competing message. However, the effect of syntactic similarity was consistent across subject groups. Hearing loss, short-term memory, processing speed, and inhibitory ability were each related to some aspects of performance by the middle-aged and older participants. Notably, substantial age-related changes in speech recognition were apparent within the group of middle-aged listeners.

Threshold of the precedence effect in noise.

Three effects that show a temporal asymmetry in the influence of interaural cues were studied through the addition of masking noise: (1) The transient precedence effect-the perceptual dominance of a leading transient over a similar lagging transient; (2) the ongoing precedence effect-lead dominance with lead and lag components that extend in time; and (3) the onset capture effect-determination by an onset transient of the lateral position of an otherwise ambiguous extended trailing sound. These three effects were evoked with noise-burst stimuli and were compared in the presence of masking noise. Using a diotic noise masker, detection thresholds for stimuli with lead/lag interaural delays of 0/500 µs were compared to those with 500/0 µs delays. None of the three effects showed a masking difference between those conditions, suggesting that none of the effects is operative at masked threshold. A task requiring the discrimination between stimuli with 500/0 and 0/500 µs interaural delays was used to determine the threshold for each effect in noise. The results showed similar thresholds in noise (10-13 dB SL) for the transient and ongoing precedence effects, but a much higher threshold (33 dB SL) for onset capture of an ambiguous trailing sound.

Influence of musical training on understanding voiced and whispered speech in noise.

This study tested the hypothesis that the previously reported advantage of musicians over non-musicians in understanding speech in noise arises from more efficient or robust coding of periodic voiced speech, particularly in fluctuating backgrounds. Speech intelligibility was measured in listeners with extensive musical training, and in those with very little musical training or experience, using normal (voiced) or whispered (unvoiced) grammatically correct nonsense sentences in noise that was spectrally shaped to match the long-term spectrum of the speech, and was either continuous or gated with a 16-Hz square wave. Performance was also measured in clinical speech-in-noise tests and in pitch discrimination. Musicians exhibited enhanced pitch discrimination, as expected. However, no systematic or statistically significant advantage for musicians over non-musicians was found in understanding either voiced or whispered sentences in either continuous or gated noise. Musicians also showed no statistically significant advantage in the clinical speech-in-noise tests. Overall, the results provide no evidence for a significant difference between young adult musicians and non-musicians in their ability to understand speech in noise.

Priming of lowpass-filtered speech affects response bias, not sensitivity, in a bandwidth discrimination task.

Priming is demonstrated when prior information about the content of a distorted, filtered, or masked auditory message improves its clarity. The current experiment attempted to quantify aspects of priming by determining its effects on performance and bias in a lowpass-filter-cutoff frequency discrimination task. Nonsense sentences recorded by a female talker were sharply lowpass filtered at a nominal cutoff frequency (F) of 0.5 or 0.75 kHz or at a higher cutoff frequency (F + ΔF). The listeners' task was to determine which interval of a two-interval-forced-choice trial contained the nonsense sentence filtered with F + ΔF. On priming trials, the interval 1 sentence was displayed on a computer screen prior to the auditory portion of the trial. The prime markedly affected bias, increasing the number of correct and incorrect interval 1 responses but did not affect overall discrimination performance substantially. These findings were supported through a second experiment that required listeners to make confidence judgments. The paradigm has the potential to help quantify the limits of speech perception when uncertainty about the auditory message is removed.