Monaural perception under dichotic conditions

Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, February 2007.Vita.Includes bibliographical references.Most people have two ears, but we can hear with only one ear. The ability to use two ears can substantially improve performance in many circumstances. There are times, however, when the addition of a second ear results in poorer performance (i.e., contra-aural interference). Contra-aural interference is of interest because it is not explained by current auditory models, it has theoretical ramifications, and its understanding could lead to improvements in the quality of life of the hearing-impaired. More generally, the techniques and results can be applied to fields in which information is combined across an array of sensors (e.g., vision with two eyes and radar arrays). This thesis includes both psychophysical measurements and black-box modeling of level discrimination. Level discrimination was chosen to study contra-aural interference since it has traditionally been considered a monaural task (dependent on only a single ear) even though the loudness of a sound depends on both ears (i.e., binaural). This thesis demonstrates that the ability to discriminate small changes in the level of a low-frequency target stimulus presented at one ear can be adversely affected by a distractor stimulus presented simultaneously and contra-aurally to the target.(cont.) The thesis focuses on conditions in which the target and distractor perceptually fuse; the dominant perception of the stimulus is a compact auditory image with a salient loudness and position and a secondary image referred to as the "time-image". Contra-aural interference was greatest when the introduction of the distractor decreased the reliability of both the perceived loudness and position of the dominant-image. Although the tasks used in this thesis are artificial, their simplicity allows for detailed computational modeling. The results are consistent with a model based on non-optimal integration of the information carried by the dominant-image and the time-image. The modeling separates the effects of internal coding noise and decision noise (criterion jitter). The techniques used to separate the internal coding noise from the criterion jitter can be applied to a broad range of psychology experiments.by Daniel E. Shub.Ph.D

FORUM:Remote testing for psychological and physiological acoustics

Acoustics research involving human participants typically takes place in specialized laboratory settings. Listening studies, for example, may present controlled sounds using calibrated transducers in sound-attenuating or anechoic chambers. In contrast, remote testing takes place outside of the laboratory in everyday settings (e.g., participants' homes). Remote testing could provide greater access to participants, larger sample sizes, and opportunities to characterize performance in typical listening environments at the cost of reduced control of environmental conditions, less precise calibration, and inconsistency in attentional state and/or response behaviors from relatively smaller sample sizes and unintuitive experimental tasks. The Acoustical Society of America Technical Committee on Psychological and Physiological Acoustics launched the Task Force on Remote Testing (https://tcppasa.org/remotetesting/) in May 2020 with goals of surveying approaches and platforms available to support remote testing and identifying challenges and considerations for prospective investigators. The results of this task force survey were made available online in the form of a set of Wiki pages and summarized in this report. This report outlines the state-of-the-art of remote testing in auditory-related research as of August 2021, which is based on the Wiki and a literature search of papers published in this area since 2020, and provides three case studies to demonstrate feasibility during practice

The role of the precedence effect in sound source lateralization

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.Includes bibliographical references (leaf 79).by Daniel E. Shub.S.M

Discrimination and identification of azimuth using spectral shape1

Monaural measurements of minimum audible angle (MAA) (discrimination between two locations) and absolute identification (AI) of azimuthal locations in the frontal horizontal plane are reported. All experiments used roving-level fixed-spectral-shape stimuli processed with nonindividualized head-related transfer functions (HRTFs) to simulate the source locations. Listeners were instructed to maximize percent correct, and correct-answer feedback was provided after every trial. Measurements are reported for normal-hearing subjects, who listened with only one ear, and effectively monaural subjects, who had substantial unilateral hearing impairments (i.e., hearing losses greater than 60 dB) and listened with their normal ears. Both populations behaved similarly; the monaural experience of the unilaterally impaired listeners was not beneficial for these monaural localization tasks. Performance in the AI experiments was similar with both 7 and 13 source locations. The average root-mean-squared deviation between the virtual source location and the reported location was 35°, the average slopes of the best fitting line was 0.82, and the average bias was 2°. The best monaural MAAs were less than 5°. The MAAs were consistent with a theoretical analysis of the HRTFs, which suggests that monaural azimuthal discrimination is related to spectral-shape discrimination

Discrimination and identification of azimuth using spectral shape1

Monaural measurements of minimum audible angle (MAA) (discrimination between two locations) and absolute identification (AI) of azimuthal locations in the frontal horizontal plane are reported. All experiments used roving-level fixed-spectral-shape stimuli processed with nonindividualized head-related transfer functions (HRTFs) to simulate the source locations. Listeners were instructed to maximize percent correct, and correct-answer feedback was provided after every trial. Measurements are reported for normal-hearing subjects, who listened with only one ear, and effectively monaural subjects, who had substantial unilateral hearing impairments (i.e., hearing losses greater than 60 dB) and listened with their normal ears. Both populations behaved similarly; the monaural experience of the unilaterally impaired listeners was not beneficial for these monaural localization tasks. Performance in the AI experiments was similar with both 7 and 13 source locations. The average root-mean-squared deviation between the virtual source location and the reported location was 35°, the average slopes of the best fitting line was 0.82, and the average bias was 2°. The best monaural MAAs were less than 5°. The MAAs were consistent with a theoretical analysis of the HRTFs, which suggests that monaural azimuthal discrimination is related to spectral-shape discrimination