Lexical and indexical cues in masking by competing speech

Three experiments were conducted using the TVM sentences, a new set of stimuli for competing speech research. These open-set sentences incorporate a cue name that allows the experimenter to direct the listener’s attention to a target sentence. The first experiment compared the relative efficacy of directing the listener’s attention to the cue name versus instructing the subject to listen for a particular talker’s voice. Results demonstrated that listeners could use either cue about equally well to find the target sentence. Experiment 2 was designed to determine whether differences in intelligibility among talkers’ voices that were noted when three utterances were presented together persisted when each talker’s sentences were presented in steady-state noise. Results of experiment 2 showed only minor intelligibility differences between talkers’ utterances presented in noise. The final experiment considered how providing accurate and inaccurate information about the target talker’s voice influenced speech recognition performance. This voice cue was found to have minimal effect on listeners’ ability to understand the target utterance or ignore a masking voice

Release and re-buildup of listeners’ models of auditory space

When listeners hear sound presented repeatedly in a room with reflections, echo threshold rises. The current experiments tested how long this buildup in echo threshold would last when exposure to a different simulated space (designated as room B) intervened before returning to the original space (designated room A). Stimuli were trains of lead–lag click pairs (room A) and trains of clicks with no reflections (room B) in an ABA sequence. After buildup in room A, echo threshold for click pairs in room A decreased in direct relation to amount of intervening exposure to room B. After 11 click pairs of room B, the effect of exposure to room A was gone. A second buildup in echo threshold in room A was not differentially affected by prior exposure to room A or a different simulated room, room C. Listeners appear to form a model when exposed to sound in a particular space, which is lost quickly upon hearing sound in a different space. Storing previous models is inefficient because the processes of buildup and breakdown occur quickly to sound in a new space

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

Manipulations of listeners’ echo perception are reflected in event-related potentials

To gain information from complex auditory scenes, it is necessary to determine which of the many loudness, pitch, and timbre changes originate from a single source. Grouping sound into sources based on spatial information is complicated by reverberant energy bouncing off multiple surfaces and reaching the ears from directions other than the source’s location. The ability to localize sounds despite these echoes has been explored with the precedence effect: Identical sounds presented from two locations with a short stimulus onset asynchrony (e.g., 1–5 ms) are perceived as a single source with a location dominated by the lead sound. Importantly, echo thresholds, the shortest onset asynchrony at which a listener reports hearing the lag sound as a separate source about half of the time, can be manipulated by presenting sound pairs in contexts. Event-related brain potentials elicited by physically identical sounds in contexts that resulted in listeners reporting either one or two sources were compared. Sound pairs perceived as two sources elicited a larger anterior negativity 100–250 ms after onset, previously termed the object-related negativity, and a larger posterior positivity 250–500 ms. These results indicate that the models of room acoustics listeners form based on recent experience with the spatiotemporal properties of sound modulate perceptual as well as later higher-level processing

Influence of Musical Training on Understanding Voiced and Whispered Speech in Noise

<div><p>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.</p></div

Onset dominance in lateralization

[[abstract]]Saberi and Perrott [Acustica 81, 272-275 (1995)] found that the in-head lateralization of a relatively long-duration pulse train could be controlled by the interaural delay of the single pulse pair that occurs at onset. The present study examined this further, using an acoustic pointer measure of lateralization, with stimulus manipulations designed to determine conditions under which lateralization was consistent with the interaural onset delay. The present stimuli were wideband pulse trains, noise-burst trains, and inharmonic complexes, 250 ms in duration, chosen for the ease with which interaural delays and correlations of select temporal segments of the stimulus could be manipulated. The stimulus factors studied were the periodicity of the ongoing part of the signal as well as the multiplicity and ambiguity of interaural delays. The results, in general, showed that the interaural onset delay controlled lateralization when the steady state binaural cues were relatively weak, either because the spectral components were only sparsely distributed across frequency or because the interaural time delays were ambiguous. Onset dominance can be disrupted by sudden stimulus changes within the train, and several examples of such changes are described. Individual subjects showed strong left-right asymmetries in onset effectiveness. The results have implications for understanding how onset and ongoing interaural delay cues contribute to the location estimates formed by the binaural auditory system