Ecological sound loudness in environmental sound representations.

Listeners recognizing environmental sounds must contend with variations in level due to the source level and the environment. Nonetheless, variations in level disrupt short-term sound recognition [Susini, Houix, Seropian, and Lemaitre (2019). J. Acoust. Soc. Am. 146(2), EL172-EL176] suggesting that loudness is encoded. We asked whether the experimental custom of setting sounds to equal levels disrupts long-term recognition, especially if it creates a mismatch with ecological loudness. Environmental sounds were played at equalized or ecological levels. Although recognition improved with increased loudness and familiarity, this relationship was unaffected by equalization or real-life experience with the source. However, sound pleasantness was altered by deviations from the ecological level.

Identification of Everyday Sounds Affects Their Pleasantness.

This study examines the role of source identification in the emotional response to everyday sounds. Although it is widely acknowledged that sound identification modulates the unpleasantness of sounds, this assumption is based on sparse evidence on a select few sounds. We gathered more robust evidence by having listeners judge the causal properties of sounds, such as actions, materials, and causal agents. Participants also identified and rated the pleasantness of the sounds. We included sounds from a variety of emotional categories, such as Neutral, Misophonic, Unpleasant, and Pleasant. The Misophonic category consists of everyday sounds that are uniquely distressing to a subset of listeners who suffer from Misophonia. Sounds from different emotional categories were paired together based on similar causal properties. This enabled us to test the prediction that a sound's pleasantness should increase or decrease if it is misheard as being in a more or less pleasant emotional category, respectively. Furthermore, we were able to induce more misidentifications by imposing spectral degradation in the form of envelope vocoding. Several instances of misidentification were obtained, all of which showed pleasantness changes that agreed with our predictions.

Who's that Knocking at My Door? Neural Bases of Sound Source Identification.

When hearing knocking on a door, a listener typically identifies both the action (forceful and repeated impacts) and the object (a thick wooden board) causing the sound. The current work studied the neural bases of sound source identification by switching listeners' attention toward these different aspects of a set of simple sounds during functional magnetic resonance imaging scanning: participants either discriminated the action or the material that caused the sounds, or they simply discriminated meaningless scrambled versions of them. Overall, discriminating action and material elicited neural activity in a left-lateralized frontoparietal network found in other studies of sound identification, wherein the inferior frontal sulcus and the ventral premotor cortex were under the control of selective attention and sensitive to task demand. More strikingly, discriminating materials elicited increased activity in cortical regions connecting auditory inputs to semantic, motor, and even visual representations, whereas discriminating actions did not increase activity in any regions. These results indicate that discriminating and identifying material requires deeper processing of the stimuli than discriminating actions. These results are consistent with previous studies suggesting that auditory perception is better suited to comprehend the actions than the objects producing sounds in the listeners' environment.

No difference in cross-modal attention or sensory discrimination thresholds in autism and matched controls.

Autism has been associated with abnormalities in sensory and attentional processing. Here, we assessed these processes independently in the visual and auditory domains using a visual contrast-discrimination task and an auditory modulation-depth discrimination task. To evaluate changes in sensory function by attention, we measured behavioral performance (discrimination accuracy) when subjects were cued to attend and respond to the same stimulus (frequent valid cue) or cued to attend to one stimulus and respond to the non-cued stimulus (infrequent invalid cue). The stimuli were presented at threshold to ensure equal difficulty across participants and groups. Results from fifteen high-functioning adult individuals with autism and fifteen matched controls revealed no significant differences in visual or auditory discrimination thresholds across groups. Furthermore, attention robustly modulated performance accuracy (performance was better for valid than invalid cues) in both sensory modalities and to an equivalent extent in both groups. In conclusion, when using this well-controlled method, we found no evidence of atypical sensory function or atypical attentional modulation in a group of high functioning individuals with clear autism symptomatology.

The Egocentric Nature of Action-Sound Associations.

Actions that produce sounds infuse our daily lives. Some of these sounds are a natural consequence of physical interactions (such as a clang resulting from dropping a pan), but others are artificially designed (such as a beep resulting from a keypress). Although the relationship between actions and sounds has previously been examined, the frame of reference of these associations is still unknown, despite it being a fundamental property of a psychological representation. For example, when an association is created between a keypress and a tone, it is unclear whether the frame of reference is egocentric (gesture-sound association) or exocentric (key-sound association). This question is especially important for artificially created associations, which occur in technology that pairs sounds with actions, such as gestural interfaces, virtual or augmented reality, and simple buttons that produce tones. The frame of reference could directly influence the learnability, the ease of use, the extent of immersion, and many other factors of the interaction. To explore whether action-sound associations are egocentric or exocentric, an experiment was implemented using a computer keyboard's number pad wherein moving a finger from one key to another produced a sound, thus creating an action-sound association. Half of the participants received egocentric instructions to move their finger with a particular gesture. The other half of the participants received exocentric instructions to move their finger to a particular number on the keypad. All participants were performing the same actions, and only the framing of the action varied between conditions by altering task instructions. Participants in the egocentric condition learned the gesture-sound association, as revealed by a priming paradigm. However, the exocentric condition showed no priming effects. This finding suggests that action-sound associations are egocentric in nature. A second part of the same session further confirmed the egocentric nature of these associations by showing no change in the priming effect after moving to a different starting location. Our findings are consistent with an egocentric representation of action-sound associations, which could have implications for applications that utilize these associations.

Priming Gestures with Sounds.

We report a series of experiments about a little-studied type of compatibility effect between a stimulus and a response: the priming of manual gestures via sounds associated with these gestures. The goal was to investigate the plasticity of the gesture-sound associations mediating this type of priming. Five experiments used a primed choice-reaction task. Participants were cued by a stimulus to perform response gestures that produced response sounds; those sounds were also used as primes before the response cues. We compared arbitrary associations between gestures and sounds (key lifts and pure tones) created during the experiment (i.e. no pre-existing knowledge) with ecological associations corresponding to the structure of the world (tapping gestures and sounds, scraping gestures and sounds) learned through the entire life of the participant (thus existing prior to the experiment). Two results were found. First, the priming effect exists for ecological as well as arbitrary associations between gestures and sounds. Second, the priming effect is greatly reduced for ecologically existing associations and is eliminated for arbitrary associations when the response gesture stops producing the associated sounds. These results provide evidence that auditory-motor priming is mainly created by rapid learning of the association between sounds and the gestures that produce them. Auditory-motor priming is therefore mediated by short-term associations between gestures and sounds that can be readily reconfigured regardless of prior knowledge.

Evidence for a basic level in a taxonomy of everyday action sounds.

We searched for evidence that the auditory organization of categories of sounds produced by actions includes a privileged or "basic" level of description. The sound events consisted of single objects (or substances) undergoing simple actions. Performance on sound events was measured in two ways: sounds were directly verified as belonging to a category, or sounds were used to create lexical priming. The category verification experiment measured the accuracy and reaction time to brief excerpts of these sounds. The lexical priming experiment measured reaction time benefits and costs caused by the presentation of these sounds prior to a lexical decision. The level of description of a sound varied in how specifically it described the physical properties of the action producing the sound. Both identification and priming effects were superior when a label described the specific interaction causing the sound (e.g. trickling) in comparison to the following: (1) more general descriptions (e.g. pour, liquid: trickling is a specific manner of pouring liquid), (2) more detailed descriptions using adverbs to provide detail regarding the manner of the action (e.g. trickling evenly). These results are consistent with neuroimaging studies showing that auditory representations of sounds produced by actions familiar to the listener activate motor representations of the gestures involved in sound production.

Auditory perception of material is fragile while action is strikingly robust.

While many psychoacoustic studies have found that listeners can recover some causal properties of sound-generating objects (such as the material), comparatively little is known about the causal properties of the sound-generating actions and how they are perceived. This article reports on a study comparing the performance of listeners required to identify either the actions or the materials used to generate sound stimuli. Stimuli were recordings of a set of cylinders of two sizes and four materials (wood, plastic, glass, metal) undergoing four different actions (scraping, rolling, hitting, bouncing). Experiment 1 tested how well each sound conveyed that it was generated with a different action or material. Experiment 2 measured both accuracy and reaction times for the identification of actions and materials. Listeners were faster and more accurate at identifying the action than the material. Even for the subset of sounds for which actions and materials were equivalently well identified, listeners were faster at identifying the action than the material. These results suggest that the auditory system is well-suited to extract information about sound-generating actions.

Binaural interference in lateralization thresholds for interaural time and level differences.

Listeners discriminated changes in either interaural time differences (ITDs) or interaural level differences (ILDs) in one noise band (the target) in the presence or absence of an uninformative spectrally-remote second noise band (the interferer). The noise bands had center frequencies of 500 and 4000 Hz and bandwidths of 50 and 400 Hz, respectively. When one band was a target, the other served as an interferer. The interferer was presented either diotically or dichotically with ITDs or ILDs that varied randomly across intervals. "Interference" was defined as occurring if the target thresholds were elevated in the presence of an interferer. For ITD discrimination, interference was greater for the 4000-Hz target than for the 500-Hz target, but for ILD discrimination, interference for the 500-Hz target was greater than or equal to that obtained for the 4000-Hz target. Larger interference effects were obtained when the interferer ITD or ILD was randomly varied, revealing that interference can be large not only for high-frequency targets but also for low-frequency targets with high-frequency interferers. The data are consistent with a model in which listeners combine lateral position across frequency with interaural information weighted according to the accuracy with which positions are encoded in each frequency region.

Detecting incipient inner-ear damage from impulse noise with otoacoustic emissions.

Audiometric thresholds and otoacoustic emissions (OAEs) were measured in 285 U.S. Marine Corps recruits before and three weeks after exposure to impulse-noise sources from weapons' fire and simulated artillery, and in 32 non-noise-exposed controls. At pre-test, audiometric thresholds for all ears were

Low-level otoacoustic emissions may predict susceptibility to noise-induced hearing loss.

In a longitudinal study with 338 volunteers, audiometric thresholds and otoacoustic emissions were measured before and after 6 months of noise exposure on an aircraft carrier. While the average amplitudes of the otoacoustic emissions decreased significantly, the average audiometric thresholds did not change. Furthermore, there were no significant correlations between changes in audiometric thresholds and changes in otoacoustic emissions. Changes in transient-evoked otoacoustic emissions and distortion-product otoacoustic emissions were moderately correlated. Eighteen ears acquired permanent audiometric threshold shifts. Only one-third of those ears showed significant otoacoustic emission shifts that mirrored their permanent threshold shifts. A Bayesian analysis indicated that permanent threshold shift status following a deployment was predicted by baseline low-level or absent otoacoustic emissions. The best predictor was transient-evoked otoacoustic emission amplitude in the 4-kHz half-octave frequency band, with risk increasing more than sixfold from approximately 3% to 20% as the emission amplitude decreased. It is possible that the otoacoustic emissions indicated noise-induced changes in the inner ear, undetected by audiometric tests. Otoacoustic emissions may therefore be a diagnostic predictor for noise-induced-hearing-loss risk.

Auditory-visual interactions in the perception of a ball's path.

We carried out two experiments to measure the combined perceptual effect of visual and auditory information on the perception of a moving object's trajectory. All visual stimuli consisted of a perspective rendering of a ball moving in a three-dimensional box. Each video was paired with one of three sound conditions: silence, the sound of a ball rolling, or the sound of a ball hitting the ground. We found that the sound condition influenced whether observers were more likely to perceive the ball as rolling back in depth on the floor of the box or jumping in the frontal plane. In a second experiment we found further evidence that the reported shift in path perception reflects perceptual experience rather than a deliberate decision process. Instead of directly judging the ball's path, observers judged the ball's speed. Speed is an indirect measure of the perceived path because, as a result of the geometry of the box and the viewing angle, a rolling ball would travel a greater distance than a jumping ball in the same time interval. Observers did judge a ball paired with a rolling sound as faster than a ball paired with a jumping sound. This auditory-visual interaction provides an example of a unitary percept arising from multisensory input.

A longitudinal study of changes in evoked otoacoustic emissions and pure-tone thresholds as measured in a hearing conservation program.

Non-linear transient-evoked otoacoustic emissions (TEOAEs) at 74dB pSPL, distortion-product otoacoustic emissions (DPOAEs) at 65/45dB SPL and pure-tone audiometry were used to detect noise-induced, inner car changes in a longitudinal study. Repeated-measures ANOVAs were made on the Noise (n=69) and Quiet (n=42) groups. The Noise group's hearing thresholds increased by 1.2 dB and DPOAE amplitude decreased by -0.9 dB. For both groups, TEOAE amplitude decreased by approximately -0.6 dB. Eight of 12 ears with permanent threshold shift (PTS) and 10 of 13 ears with temporary threshold shift (TTS) showed TEOAE decrements or low baseline TEOAE amplitudes. Fewer TTS and PTS ears also showed DPOAE decrements, and there was never a DPOAE decrement without a corresponding TEOAE decrement or low TEOAE baseline. Some TTS ears showed permanent emission decrements. Although otoacoustic emissions show promise in detecting noise-induced inner ear changes, it is premature to use them in hearing conservation programs.

Distortion-Product Otoacoustic Emissions as a Screening Tool for Noise-Induced Hearing Loss.

Noise-induced hearing loss includes both temporary (TTS) and permanent (PTS) threshold shifts. Although TTS and PTS have many similarities, their underlying mechanisms are different. Both TTS and PTS are seen in hearing-conservation programs, making it important to consider both when making physiological measurements of inner-ear damage in applied settings. There are many ways that physiological mechanisms could be useful in screening for NIHL. Can normal-hearing and NIHL ears be differentiated from one another? Can the physiological measure be used in place of behavioural hearing-threshold measures of TTS and PTS? Can it be used to indicate sub-clinical damage (i.e., noise-induced permanent alterations to the inner ear without a corresponding hearing decrement)? Can it be used to indicate pre-clinical hearing loss (i.e., the sub-clinical damage eventually turns into hearing loss)? Finally, can the physiological measure be used to predict susceptibility to NIHL? Evoked otoacoustic emissions (EOAEs) depend on normal outer hair cells for their generation. Because this is the site in the inner ear in humans that is most susceptible to noise, there has been considerable interest in the application of EOAEs to NIHL screening. In this review, the application of distortion-product EOAEs (DPOAEs) is considered for this purpose, emphasizing work from our laboratory, but including that of others as well. Wherever possible, we compare the performance of DPOAEs as a screening tool to transient-evoked otoacoustic emissions (TEOAEs). We emphasize the importance of how well DPOAEs perform in screening for NIHL in individuals rather than for groups of people; the importance of using large numbers of subjects; and the importance of longitudinal studies.