Laurie M. Heller

Reliability of transient-evoked otoacoustic emissions

Objective: This investigation addressed four factors affecting transient‐evoked otoacoustic emission (TEOAE) reliability: 1) The effect of evoking‐stimulus level, 2) the effect of analyzing bandwidth, 3) the effect of slight‐mild hearing loss, and 4) the effect of variability in the stimulus spectrum. Design: TEOAEs at 80, 74, 68, and 62 dB pSPL evoking‐stimulus levels were measured in 25 ears spanning a range of hearing levels from normal to mild hearing loss for a minimum of 10 test sessions. Reliability was assessed for 1/6‐, 1/3‐ 1/2‐, and 1‐octave analyzing bandwidths. Results: Evoking‐stimulus level, hearing loss, and center frequency did not significantly affect reliability. With decreasing analyzing bandwidth, reliability decreased. Intrasubject test‐retest standard deviations were 1.2 dB for a broadband analyzing bandwidth and 1.4, 1.5, 1.6, and 1.8 dB for 1‐, 1/2‐, 1/3‐, and 1/6‐octave analyzing bandwidths, respectively. Stimulus variability within narrower bandwidths was to sufficient magnitude to influence test‐retest reliability, and attempts to correct for the variations in stimulus spectrum were unsuccessful. Slopes of the input‐output functions differed across frequencies, with shallower slopes at higher frequencies. Conclusions: In general, TEOAE amplitude is highly reliable. For those individuals in this study who were more variable, the variability was at low frequencies or across the entire frequency spectrum. For clinical applications, the choice of analyzing bandwidth should be based on consideration of both frequency specificity (where narrow analyzing bandwidths are optimal) and reliability(where wide analyzing bandwidths are optimal).

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.

Effect of negative middle-ear pressure on transient-evoked otoacoustic emissions.

Objective: The purpose of the study was to illustrate the effect of negative middle‐ear pressure (MEP) on both the stimulus and response of transient‐evoked otoacoustic emissions (TEOAEs) and the effect of compensating for negative pressure in the middle ear by pneumatically introducing pressure into the ear canal. Simulation of negative MEP by introducing positive pressure into the ear canal also was examined. Design: TEOAEs were measured over 6 mo in a subject who frequently had negative MEP out to ‐150 daPa. Compensation was done for MEPs of ‐105, ‐135, and ‐165 daPa. Simulation of negative pressure was done for these same pressures. The effect of a pressure differential across the eardrum on the stimulus spectrum was measured at 100, 200, and 300 daPa. All measurements were made on the same subject. Results: Small amounts of negative MEP significantly affected both stimulus and response spectra. The simulated negative MEP approximated actual MEP at MEPs of ‐105 and ‐135 daPa. At ‐165 daPa, a divergence between the two spectra occurred below 2.0 kHz. Compensation for negative MEP by pneumatically introducing pressure into the ear canal essentially returned both spectra to that seen when the MEP was close to ambient pressure, at least for frequencies above 1.5 to 2.0 kHz. At lower frequencies, compensation resulted in increased TEOAE amplitude relative to the amplitude at ambient pressure. Conclusions: Small amounts of negative MEP may affect TEOAE spectra and potentially influence the reliability of the test. For long‐term monitoring of TEOAEs, MEPs either should be near ambient pressure or should be compensated for by an equivalent pressure in the ear canal.

Interference in detection of interaural delay in a sinusoidally amplitude‐modulated tone produced by a second, spectrally remote sinusoidally amplitude‐modulated tone

Sensitivity to interaural time delays (ITDs) within high-frequency sinusoidally amplitude-modulated (SAM) target tones was measured in the presence of a second, spectrally remote diotic SAM tone (termed an interferer). Targets and interferers were 100% modulated at 250 Hz and each was presented at 77 dB SPL for a duration of 250 ms. The modulations of targets and interferers were either in-phase or out-of-phase. In the first experiment, when the target SAM tone was centered at 4 kHz, interferers were centered at either 500 Hz, 1 kHz, or 2 kHz. Threshold ITDs were substantially increased in the presence of the interferers as compared to when the targets were presented in isolation. The greatest effects were observed with interferers centered at 500 Hz and 1 kHz. In the second experiment, when the target SAM tone was centered at 2 kHz, interferers were centered at either 500 Hz or 4 kHz. Threshold ITDs increased in the presence of either interferer, but the greatest increase occurred in the presence of the 500-Hz SAM tone. In the third experiment, it was found that presenting the low-frequency SAM tones continuously resulted in less interference than did presenting the interferers and targets coincidently. In all three experiments, the effects produced by the interferers did not depend upon whether they were modulated in-phase or out-of-phase with the target. Taken together, the data argue against the notion that the interference could result from a peripheral, monaural interaction between target and interferer waveforms.

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.

When sound effects are better than the real thing

Sound effects technicians (‘‘Foley Artists’’) have long exploited the fact that two physically different events can produce perceptually similar sounds, such as squeezing a box of cornstarch to imitate footsteps in the snow. Although some sound effects succeed because they produce acoustic waveforms nearly identical to the sounds they are imitating (their targets), in other cases there are obvious acoustic differences between sound effects and their targets. Those differences may provide information about which acoustic features are essential, and which are extraneous, for auditory recognition of an event. To address this question, twelve pairs of sound effects and their associated target events were recorded. Listeners attempted to identify each sound as it was presented over headphones. Next, the listeners were informed of the target sound (e.g., footsteps in the snow) and were asked to rate the sound’s realism. The sound effects were sometimes judged as more realistic than recordings of the target events. Acoustic differences between the waveforms of the most realistic sound effects and their targets were interpreted in terms of psychoacoustic principles.

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 objects 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 balls path, observers judged the balls 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.

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.

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.