The Dog Soundscape: Recurrence, Emotional Impact, Acoustics, and Implications for Dog Observations and Dog-Human Interactions.

While numerous dog behavioral studies use environmental sounds, the dog soundscape remains undescribed. We proposed a list of 79 sounds classified into six categories: Dog, Dog accessories, Human, city and vehicles, Garden, countryside and weather, and Household. In a survey, 620 dog owners scored the frequency of their dog's exposure to, and thus, the recurrence of, each of the 79 sounds, from never to daily. The survey results also extended to about 25 sounds the number of acknowledged sounds that are likely to elicit stress or fear, that is, negative emotional sensitivity, in dogs. Sound recurrence and emotional sensitivity were not correlated, showing no beneficial effect of frequent exposure to, and no deleterious effect of scarcity of, sound events. We suggest that for the sake of dog welfare, researchers, veterinarians, trainers, and owners may limit dogs' exposure to the sensitive sounds identified in the study during their dog observations and dog-human interactions. A corpus of 84 sounds was collected. The sounds were spectrally analyzed by determining their F0 and 10 dB bandwidth parameters. At the lowest sound frequencies, where canine hearing is poorest, negative emotional sensitivity was generally low. At the middle and high sound center frequencies/F0s, sensitivity greatly varied from lowest to highest, which is incompatible with both the general assumption and dog auditory detection thresholds. How emotional sensitivity relates to F0 (pitch) and hearing sensitivity remains undetermined. Finally, we suggest that future behavioral audiometric studies of dogs may maximize the spectral spread of each sound while minimizing the spectral overlap between sounds so as to reduce both the testing duration and the risk of inadvertently targeting or, conversely, missing frequency-dependent hearing impairments.

Are dogs with congenital hearing and/or vision impairments so different from sensory normal dogs? A survey of demographics, morphology, health, behaviour, communication, and activities.

The births of domestic dogs with pigment deletion and associated congenital hearing and/or vision impairments are increasing, as a result of mutations of certain genes expressing popular coat colour patterns (Merle, piebald, Irish spotting). The future of these dogs is often pessimistic (early euthanasia or placement in rescues/fosters, lack of interactions and activities for adults). These pessimistic scenarios result from popular assumptions predicting that dogs with congenital hearing/vision impairments exhibit severe Merle-related health troubles (cardiac, skeletal, neurological), impairment-related behavioural troubles (aggressiveness, anxiety), and poor capacities to communicate, to be trained, and to be engaged in leisure or work activities. However, there is no direct scientific testing, and hence no evidence or refutation, of these assumptions. We therefore addressed an online questionnaire to owners of 223 congenitally sensory impaired (23 vision impaired, 63 hearing impaired, 137 hearing and vision impaired) and 217 sensory normal dogs from various countries. The sensory normal cohort was matched in age, lifetime with owner, breed and sex with the sensory impaired cohort, and was used as a baseline. The questionnaire assessed demographics, morphology, sensory impairments, health and behavioural troubles, activities, and dog-owner communication. Most hearing and/or vision impaired dogs exhibited abnormal pigment deletion in their coat and irises. Vision impaired dogs additionally exhibited ophthalmic abnormalities typically related to Merle. The results are opposed to all above-listed assumptions, except for neurological troubles, which were more frequently reported in sensory impaired dogs. However, we suggest that this finding could be partially accounted for by a lack of diagnosis of breed-related drug sensitivity and impairment-related compulsive behaviours. Results about communication and activities are particularly optimistic. The need for future studies of numerous dogs from various breeds tested for Merle, piebald and medical-drug-resistance genes, and the beneficial effects that present and future research may have on the future of sensory impaired dogs, are discussed.

Auditory Time-Frequency Masking for Spectrally and Temporally Maximally-Compact Stimuli.

Many audio applications perform perception-based time-frequency (TF) analysis by decomposing sounds into a set of functions with good TF localization (i.e. with a small essential support in the TF domain) using TF transforms and applying psychoacoustic models of auditory masking to the transform coefficients. To accurately predict masking interactions between coefficients, the TF properties of the model should match those of the transform. This involves having masking data for stimuli with good TF localization. However, little is known about TF masking for mathematically well-localized signals. Most existing masking studies used stimuli that are broad in time and/or frequency and few studies involved TF conditions. Consequently, the present study had two goals. The first was to collect TF masking data for well-localized stimuli in humans. Masker and target were 10-ms Gaussian-shaped sinusoids with a bandwidth of approximately one critical band. The overall pattern of results is qualitatively similar to existing data for long maskers. To facilitate implementation in audio processing algorithms, a dataset provides the measured TF masking function. The second goal was to assess the potential effect of auditory efferents on TF masking using a modeling approach. The temporal window model of masking was used to predict present and existing data in two configurations: (1) with standard model parameters (i.e. without efferents), (2) with cochlear gain reduction to simulate the activation of efferents. The ability of the model to predict the present data was quite good with the standard configuration but highly degraded with gain reduction. Conversely, the ability of the model to predict existing data for long maskers was better with than without gain reduction. Overall, the model predictions suggest that TF masking can be affected by efferent (or other) effects that reduce cochlear gain. Such effects were avoided in the experiment of this study by using maximally-compact stimuli.

Corrigendum: Perceptual factors contribute more than acoustical factors to sound localization abilities with virtual sources.

[This corrects the article on p. 451 in vol. 8, PMID: 25688182.].

Auditory azimuthal localization performance in water as a function of prior exposure.

OBJECTIVE: We report two psychoacoustical experiments that assessed the relationship between auditory azimuthal localization performance in water and duration of prior exposure to the milieu. BACKGROUND: The adaptability of spatial hearing abilities has been demonstrated in air for both active and passive exposures to altered localization cues. Adaptability occurred faster and was more complete for elevation perception than for azimuth perception. In water, spatial hearing is believed to solely rely on smaller than normal cues-to-azimuth: interaural time differences. This should produce a medial bias in localization judgments toward the center of the horizontal plane, unless the listeners have adapted to the environment. METHOD: Azimuthal localization performance was measured in seawater for eight azimuthal directions of a low-frequency (< 500 Hz) auditory target. Seventeen participants performed a forced-choice task in Experiment 1. Twenty-eight other participants performed a pointing task in Experiment 2. RESULTS: In both experiments we observed poor front/back discrimination but accurate left/right discrimination, regardless of prior exposure. A medial bias was found in azimuth perception, whose size decreased as the exposure duration of the participant increased. CONCLUSION: The study resembles earlier results showing that passive exposure to altered azimuth cues elicits the adaptability of internal audio-spatial maps, that is, the behavioral plasticity of spatial hearing abilities. APPLICATION: Studies of the adaptability of the auditory system to altered spatial information may yield practical implications for scuba divers, hearing-impaired listeners with reduced sensitivity to spatial cues, and various normal-hearing users of virtual auditory displays.

Perceptual factors contribute more than acoustical factors to sound localization abilities with virtual sources.

Human sound localization abilities rely on binaural and spectral cues. Spectral cues arise from interactions between the sound wave and the listener's body (head-related transfer function, HRTF). Large individual differences were reported in localization abilities, even in young normal-hearing adults. Several studies have attempted to determine whether localization abilities depend mostly on acoustical cues or on perceptual processes involved in the analysis of these cues. These studies have yielded inconsistent findings, which could result from methodological issues. In this study, we measured sound localization performance with normal and modified acoustical cues (i.e., with individual and non-individual HRTFs, respectively) in 20 naïve listeners. Test conditions were chosen to address most methodological issues from past studies. Procedural training was provided prior to sound localization tests. The results showed no direct relationship between behavioral results and an acoustical metrics (spectral-shape prominence of individual HRTFs). Despite uncertainties due to technical issues with the normalization of the HRTFs, large acoustical differences between individual and non-individual HRTFs appeared to be needed to produce behavioral effects. A subset of 15 listeners then trained in the sound localization task with individual HRTFs. Training included either visual correct-answer feedback (for the test group) or no feedback (for the control group), and was assumed to elicit perceptual learning for the test group only. Few listeners from the control group, but most listeners from the test group, showed significant training-induced learning. For the test group, learning was related to pre-training performance (i.e., the poorer the pre-training performance, the greater the learning amount) and was retained after 1 month. The results are interpreted as being in favor of a larger contribution of perceptual factors than of acoustical factors to sound localization abilities with virtual sources.

Simultaneous masking additivity for short Gaussian-shaped tones: spectral effects.

Laback et al. [(2011). J. Acoust. Soc. Am. 129, 888-897] investigated the additivity of nonsimultaneous masking using short Gaussian-shaped tones as maskers and target. The present study involved Gaussian stimuli to measure the additivity of simultaneous masking for combinations of up to four spectrally separated maskers. According to most basilar membrane measurements, the maskers should be processed linearly at the characteristic frequency (CF) of the target. Assuming also compression of the target, all masker combinations should produce excess masking (exceeding linear additivity). The results for a pair of maskers flanking the target indeed showed excess masking. The amount of excess masking could be predicted by a model assuming summation of masker-evoked excitations in intensity units at the target CF and compression of the target, using compressive input/output functions derived from the nonsimultaneous masking study. However, the combinations of lower-frequency maskers showed much less excess masking than predicted by the model. This cannot easily be attributed to factors like off-frequency listening, combination tone perception, or between-masker suppression. It was better predicted, however, by assuming weighted intensity summation of masker excitations. The optimum weights for the lower-frequency maskers were smaller than one, consistent with partial masker compression as indicated by recent psychoacoustic data.

Auditory efferents facilitate sound localization in noise in humans.

The mammalian auditory system contains descending neural pathways, some of which project onto the cochlea via the medial olivocochlear (MOC) system. The function of this efferent auditory system is not entirely clear. Behavioral studies in animals with olivocochlear (OC) lesions suggest that the MOC serves to facilitate sound localization in noise. In the current work, noise-induced OC activity (the OC reflex) and sound-localization performance in noise were measured in normal-hearing humans. Consistent with earlier studies, both measures were found to vary substantially across individuals. Importantly, significant correlations were observed between OC-reflex strength and the effect of noise on sound-localization performance; the stronger the OC reflex, the less marked the effect of noise. These results suggest that MOC activation by noise helps to counteract the detrimental effects of background noise on neural representations of direction-dependent spectral features, which are especially important for accurate localization in the up/down and front/back dimensions.

Additivity of nonsimultaneous masking for short Gaussian-shaped sinusoids.

The additivity of nonsimultaneous masking was studied using Gaussian-shaped tone pulses (referred to as Gaussians) as masker and target stimuli. Combinations of up to four temporally separated Gaussian maskers with an equivalent rectangular bandwidth of 600 Hz and an equivalent rectangular duration of 1.7 ms were tested. Each masker was level-adjusted to produce approximately 8 dB of masking. Excess masking (exceeding linear additivity) was generally stronger than reported in the literature for longer maskers and comparable target levels. A model incorporating a compressive input/output function, followed by a linear summation stage, underestimated excess masking when using an input/output function derived from literature data for longer maskers and comparable target levels. The data could be predicted with a more compressive input/output function. Stronger compression may be explained by assuming that the Gaussian stimuli were too short to evoke the medial olivocochlear reflex (MOCR), whereas for longer maskers tested previously the MOCR caused reduced compression. Overall, the interpretation of the data suggests strong basilar membrane compression for very short stimuli.

Individual differences and left/right asymmetries in auditory space perception. I. Localization of low-frequency sounds in free field.

The number of subjects in studies on human spatial hearing is generally small. Therefore, individual differences and the factors underlying variability are unknown. In this study, we investigated across-listener variability in auditory localization abilities in a group of 50 naïve adults with normal hearing. Targets were trains of low-frequency noise bursts presented to 1 of 12 hidden speakers in the azimuthal plane. We observed less across-listener variability in the variance of individual responses but more in the root-mean-square and signed errors, which tended to increase with target angle. One third of the listeners demonstrated systematically smaller signed errors with left-sided targets than with right-sided ones. These asymmetries were observed less frequently in left-handers and females than in right-handers and males. Performance was not correlated with age. About 4 of 6 listeners trained with sensory feedback showed no reduction of asymmetries with training but rather showed a reduction in errors on their "best" side. Across-listener variability in the asymmetry of brain organization, notably linked to handedness or gender, is discussed.

Temporal effects in simultaneous masking with on- and off-frequency noise maskers: effects of signal frequency and masker level.

Temporal effects in simultaneous masking were measured as a function of masker level for an on-frequency broadband masker and an off-frequency narrow-band masker for signal frequencies of 750, 1730, and 4000 Hz. The on-frequency masker was 10 equivalent rectangular bandwidths (ERBs) wide and centered at the signal frequency; the off-frequency masker was 500 Hz wide and its lower frequency edge was 1.038 ERBs higher in frequency than the signal. The primary goal of the study was to determine whether previously observed differences regarding the effects of signal frequency and masker level on the temporal effect for these two different types of masker might be due to considerably different signal levels at threshold. Despite similar masked thresholds, the effects of signal frequency and masker level in the present study were different for the two masker types. The temporal effect was significant for the two highest frequencies and absent for the lowest frequency in the presence of the broadband masker, but was more or less independent of frequency for the narrow-band masker. The temporal effect increased but then decreased as a function of level for the broadband masker (at the two higher signal frequencies, where there was a temporal effect), but increased and reached an asymptote for the narrow-band masker. Despite the different effects of signal frequency and masker level, the temporal effects for both types of masker can be understood in terms of a basilar-membrane input-output function that becomes more linear during the course of masker stimulation.

Effectiveness of narrow-band versus tonal off-frequency maskers.

The present study was a follow-up to a pilot study in which it was found that a 500-Hz-wide narrow-band noise (NBN) masker produced more masking than a tonal (T) masker for signal frequencies both above and below the masker frequency. The aim of the present study was to determine to what extent these results were influenced by an interaction of the relatively rapid temporal envelope fluctuations of the NBN and the short (10-ms) duration of the signal. In the first experiment, the masking produced by a regular NBN, a low-noise noise (LNN), and a T was compared. The LNN produced less masking than the NBN, and about as much as the T, suggesting that the inherent amplitude fluctuations in the NBN were largely responsible for the greater masking produced by that masker. In the second experiment, the masking produced by a regular NBN was compared with that by a T for a signal duration of 10 or 200 ms. The difference in masking between the two maskers was reduced or eliminated when the signal duration was 200 ms, because the threshold in the presence of the NBN masker decreased more with increasing signal duration. This could reflect a decreased "confusion" between the signal and the inherent fluctuations of the NBN masker.

The neuroanatomical substrate of sound duration discrimination.

We investigated the neuroanatomical substrate of sound duration discrimination, using the same experimental design as in a previous study on sound intensity discrimination [J. Neurosci. 18 (16) (1998) 6388]. Seven normal subjects were trained to detect deviant sounds presented with a slightly longer duration than a 300 ms long standard harmonic sound, using a Go/No Go paradigm. Individual psychometric curves were assessed using a three-step psychoacoustic procedure. Subjects were then scanned while passively listening to the standard sound, and while discriminating changes in sound duration at four different performance levels (d'=1.5, 2.5, 3.5 and 4.5). Analysis of regional cerebral blood flow (rCBF) data outlined activation, during the discrimination conditions, of a right hemispheric fronto-parietal network very similar to the one previously observed for intensity discrimination, as well as additional activation in the right prefrontal cortex (Brodmann Area (BA) 10), bilateral basal ganglia and cerebellar hemispheres. These findings suggest that discrimination of sound duration, as for discrimination of sound intensity, involves two cerebral networks: a supramodal right fronto-parietal cortical network responsible for allocation of sensory attentional resources, and a network of regions such as the basal ganglia, cerebellum, and right prefrontal cortex, more specifically involved in the temporal aspects of the discrimination task.