Vigilance to Spatialized Auditory Displays: Initial Assessment of Performance and Workload.

Objective: The present study was designed to evaluate human performance and workload associated with an auditory vigilance task that required spatial discrimination of auditory stimuli.

Background: Spatial auditory displays have been increasingly developed and implemented into settings that require vigilance toward auditory spatial discrimination and localization (e.g.

Pre-stimulus brain state predicts auditory pattern identification accuracy.

Recent studies show that pre-stimulus band-specific power and phase in the electroencephalogram (EEG) can predict accuracy on tasks involving the detection of near-threshold stimuli. However, results in the auditory modality have been mixed, and few works have examined pre-stimulus features when more complex decisions are made (e.g.

Confidence tracks sensory- and decision-related ERP dynamics during auditory detection.

Recent research has focused on measuring neural correlates of metacognitive judgments in decision and post-decision processes during memory retrieval and categorization. However, many tasks (e.g.

Sustained frontal midline theta enhancements during effortful listening track working memory demands.

Recent studies demonstrate that frontal midline theta power (4-8 Hz) enhancements in the electroencephalogram (EEG) relate to effortful listening. It has been proposed that these enhancements reflect working memory demands. Here, the need to retain auditory information in working memory was manipulated in a 2-interval 2-alternative forced-choice delayed pitch discrimination task ("Which interval contained the higher pitch?").

Enhanced auditory spatial performance using individualized head-related transfer functions: An event-related potential study.

This study examined event-related potential (ERP) correlates of auditory spatial benefits gained from rendering sounds with individualized head-related transfer functions (HRTFs). Noise bursts with identical virtual elevations (0°-90°) were presented back-to-back in 5-10 burst "runs" in a roving oddball paradigm. Detection of a run's start (i.

Modeling Two-Channel Speech Processing With the EPIC Cognitive Architecture.

An important application of cognitive architectures is to provide human performance models that capture psychological mechanisms in a form that can be "programmed" to predict task performance of human-machine system designs. Although many aspects of human performance have been successfully modeled in this approach, accounting for multitalker speech task performance is a novel problem. This article presents a model for performance in a two-talker task that incorporates concepts from psychoacoustics, in particular, masking effects and stream formation.

Enhancing listener strategies using a payoff matrix in speech-on-speech masking experiments.

Speech recognition was measured as a function of the target-to-masker ratio (TMR) with syntactically similar speech maskers. In the first experiment, listeners were instructed to report keywords from the target sentence. Data averaged across listeners showed a plateau in performance below 0 dB TMR when masker and target sentences were from the same talker.

Do you hear where I hear?: isolating the individualized sound localization cues.

It is widely acknowledged that individualized head-related transfer function (HRTF) measurements are needed to adequately capture all of the 3D spatial hearing cues. However, many perceptual studies have shown that localization accuracy in the lateral dimension is only minimally decreased by the use of non-individualized head-related transfer functions. This evidence supports the idea that the individualized components of an HRTF could be isolated from those that are more general in nature.

Effects of target-masker contextual similarity on the multimasker penalty in a three-talker diotic listening task.

In many multitalker listening tasks, the degradation in performance that occurs when the number of interfering talkers increases from one to two is much larger than would be predicted from the corresponding decrease in the signal-to-noise ratio (SNR). In this experiment, a variety of contextually-relevant speech maskers, contextually-irrelevant speech maskers and non-speech maskers were used to examine the impact that the characteristics of the interfering sound sources have on the magnitude of this "multimasker penalty." The results show that a significant multimasker penalty only occurred in cases where two specific conditions were met: 1) the stimulus contained at least one contextually-relevant masker that could be confused with the target; and 2) the signal-to-noise ratio of the target relative to the combined masker stimulus was less than 0 dB.

Effects of bandwidth on auditory localization with a noise masker.

Although high-frequency content is known to be critically important for the accurate location of isolated sounds, relatively little is known about the importance of high-frequency spectral content for the localization of sounds in the presence of a masker. In this experiment, listeners were asked to identify the location of a pulsed-noise target in the presence of a randomly located continuous noise masker. Both the target and masker were low-pass filtered at one of eight cutoff frequencies ranging from 1 to 16 kHz, and the signal-to-noise ratio was varied from -12 to +12 dB.

Multitalker speech perception with ideal time-frequency segregation: effects of voice characteristics and number of talkers.

When a target voice is masked by an increasingly similar masker voice, increases in energetic masking are likely to occur due to increased spectro-temporal overlap in the competing speech waveforms. However, the impact of this increase may be obscured by informational masking effects related to the increased confusability of the target and masking utterances. In this study, the effects of target-masker similarity and the number of competing talkers on the energetic component of speech-on-speech masking were measured with an ideal time-frequency segregation (ITFS) technique that retained all the target-dominated time-frequency regions of a multitalker mixture but eliminated all the time-frequency regions dominated by the maskers.

Effect of target-masker similarity on across-ear interference in a dichotic cocktail-party listening task.

Similarity between the target and masking voices is known to have a strong influence on performance in monaural and binaural selective attention tasks, but little is known about the role it might play in dichotic listening tasks with a target signal and one masking voice in the one ear and a second independent masking voice in the opposite ear. This experiment examined performance in a dichotic listening task with a target talker in one ear and same-talker, same-sex, or different-sex maskers in both the target and the unattended ears. The results indicate that listeners were most susceptible to across-ear interference with a different-sex within-ear masker and least susceptible with a same-talker within-ear masker, suggesting that the amount of across-ear interference cannot be predicted from the difficulty of selectively attending to the within-ear masking voice.

Effects of periodic masker interruption on the intelligibility of interrupted speech.

When listeners hear a target signal in the presence of competing sounds, they are quite good at extracting information at instances when the local signal-to-noise ratio of the target is most favorable. Previous research suggests that listeners can easily understand a periodically interrupted target when it is interleaved with noise. It is not clear if this ability extends to the case where an interrupted target is alternated with a speech masker rather than noise.

Cocktail party listening in a dynamic multitalker environment.

A priori information about the location of the target talker plays a critical'role in cocktailparty listening tasks, but little is known about the influence of imperfect spatial information in situations in which the listener has some knowledge about the location of the target speech but does not know its exact location prior to hearing the stimulus. In this study, spatial uncertainty was varied by adjusting the probability that the target talker in a multitalker stimulus would change locations at the end of each trial. The results show that listeners can adapt their strategies according to the statistical properties of a dynamic acoustic environment but that this adaptation is a relatively slow process that may require dozens of trials to complete.

Isolating the energetic component of speech-on-speech masking with ideal time-frequency segregation.

When a target speech signal is obscured by an interfering speech wave form, comprehension of the target message depends both on the successful detection of the energy from the target speech wave form and on the successful extraction and recognition of the spectro-temporal energy pattern of the target out of a background of acoustically similar masker sounds. This study attempted to isolate the effects that energetic masking, defined as the loss of detectable target information due to the spectral overlap of the target and masking signals, has on multitalker speech perception. This was achieved through the use of ideal time-frequency binary masks that retained those spectro-temporal regions of the acoustic mixture that were dominated by the target speech but eliminated those regions that were dominated by the interfering speech.

Monaural speech segregation using synthetic speech signals.

When listening to natural speech, listeners are fairly adept at using cues such as pitch, vocal tract length, prosody, and level differences to extract a target speech signal from an interfering speech masker. However, little is known about the cues that listeners might use to segregate synthetic speech signals that retain the intelligibility characteristics of speech but lack many of the features that listeners normally use to segregate competing talkers. In this experiment, intelligibility was measured in a diotic listening task that required the segregation of two simultaneously presented synthetic sentences.

Audio and visual cues in a two-talker divided attention speech-monitoring task.

Although audiovisual (AV) cues are known to improve speech intelligibility in difficult listening environments, little is known about their role in divided attention tasks that require listeners to monitor multiple talkers at the same time. In this experiment, a call-sign-based multitalker listening test was used to evaluate performance in two-talker AV configurations that combined zero, one, or two channels of visual information (neither, one, or both talkers visible) with zero, one, or two channels of audio information (no audio, both talkers played from the same loudspeaker, and both talkers played through different, spatially separated loudspeakers). The results were analyzed to determine the relative performance levels that would occur with each AV configuration with target information that was equally likely to originate from either of the two talkers in the stimulus.

Interference from audio distracters during speechreading.

Although many audio-visual speech experiments have focused on situations where the presence of an incongruent visual speech signal influences the perceived utterance heard by an observer, there are also documented examples of a related effect in which the presence of an incongruent audio speech signal influences the perceived utterance seen by an observer. This study examined the effects that different distracting audio signals had on performance in a color and number keyword speechreading task. When the distracting sound was noise, time-reversed speech, or continuous speech, it had no effect on speechreading.

Precedence-based speech segregation in a virtual auditory environment.

When a masking sound is spatially separated from a target speech signal, substantial releases from masking typically occur both for speech and noise maskers. However, when a delayed copy of the masker is also presented at the location of the target speech (a condition that has been referred to as the front target, right-front masker or F-RF configuration), the advantages of spatial separation vanish for noise maskers but remain substantial for speech maskers. This effect has been attributed to precedence, which introduces an apparent spatial separation between the target and masker in the F-RF configuration that helps the listener to segregate the target from a masking voice but not from a masking noise.

The impact of hearing protection on sound localization and orienting behavior.

The effect of hearing protection devices (HPDs) on sound localization was examined in the context of an auditory-cued visual search task. Participants were required to locate and identify a visual target in a field of 5, 20, or 50 visual distractors randomly distributed on the interior surface of a sphere. Four HPD conditions were examined: earplugs, earmuffs, both earplugs and earmuffs simultaneously (double hearing protection), and no hearing protection.

Across-ear interference from parametrically degraded synthetic speech signals in a dichotic cocktail-party listening task.

Recent results have shown that listeners attending to the quieter of two speech signals in one ear (the target ear) are highly susceptible to interference from normal or time-reversed speech signals presented in the unattended ear. However, speech-shaped noise signals have little impact on the segregation of speech in the opposite ear. This suggests that there is a fundamental difference between the across-ear interference effects of speech and nonspeech signals.

The isoazimuthal perception of sounds across distance: a preliminary investigation into the location of the audio egocenter.

Evidence indicates that both visual and auditory input may be represented in multiple frames of reference at different processing stages in the nervous system. Most models, however, have assumed that unimodal auditory input is first encoded in a head-centered reference frame. The present work tested this conjecture by measuring the subjective auditory egocenter in six blindfolded listeners who were asked to match the perceived azimuths of sounds that were alternately played between a surrounding arc of far-field speakers and a hand-held point source located three different distances from the head.

Within-ear and across-ear interference in a dichotic cocktail party listening task: effects of masker uncertainty.

Increases in masker variability have been shown to increase the effects of informational masking in non-speech listening tasks, but relatively little is known about the influence that masker uncertainty has on the informational components of speech-on-speech masking. In this experiment, listeners were asked to extract information from a target phrase that was presented in their right ear while ignoring masking phrases that were presented in the same ear as the target phrase and in the ear opposite the target phrase. The level of masker uncertainty was varied by holding constant or "freezing" the talkers speaking the masking phrases, the semantic content used in the masking phrases, or both the talkers and the semantic content in the masking phrases within each block of 120 trials.