Sound localization: information theory analysis

Sound localization has been studied extensively. Curiously, although much is known about factors that affect errors, little is known about factors that influence response time. Three experiments were performed in an attempt to identify the separate influence of each of several different factors. All trials used a single broadband noise signal emanating from one of a subset of six loudspeakers equally spaced around the participant in the azimuthal plane. Both the size of the subset and the balance of relative probabilities from speaker to speaker were altered to evaluate the relationship between information content and the dependent variable, choice reaction time. Choice reaction time was found to be related to the information content of the sound stimulus in all cases. It was also found to be related to the presence of pairs of speakers that were symmetrically opposed in front of the behind the participant. Models of choice reaction time in a sound localization task have clear implications for practice. For example, they suggest that multiple auditory collision warnings may endanger drivers.     

Sound localization in large mammals: Localization of complex sounds by horses.

The idea that large mammals localize sounds more accurately than small mammals has been noted frequently and is usually explained by reference to their large interaural distance and the correspondingly broad binaural time (Δt) and spectral (Δfi) differences between their 2 ears. In Exps I and II, sound-localization thresholds for single clicks and 100-msec noise bursts were determined in 5 horses, and the magnitude of the binaural time (Δt) and spectral (Δfi) cues for sound direction were measured in Exp III with 1 horse. Results show that although Ss had relatively large interaural distances and physically broad binaural-localization cues available to them, their sound direction thresholds were markedly poorer than those of other large mammals--averaging 22° for noise and 30° for clicks. It appears that sound-localization acuity is not determined simply by the physical availability of binaural cues. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sound localization acuity in very young infants: An observer-based testing procedure.

Infants 8 to 28 weeks of age were tested to determine the smallest sound shift off midline and along the horizontal axis that could be reliably discriminated, that is, minimum audible angle. Both sound-shift and no-shift trials were presented. For each trial, an observer decided, based solely on the infant's behavior, whether the sound shifted location (i.e., an observer-based yes–no task). To isolate sensory from nonsensory factors, analyses were performed on d′ scores. The results indicated increasing localization acuity with age. The video records revealed numerous auditory orienting behaviors (e.g., alerting, quieting, and lateral head and eye movements) and highlighted the value of not requiring that specific behavioral responses be performed on sound-shift trials. Possible factors contributing to these developmental trends are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sound localization in pigeon (Columba livia).

The presence of a binaurally activated nucleus (nucleus laminaris) in the hindbrain of birds suggests that they may be capable of binaural sound localization. In this report, after verification that pigeons were capable of either homing or scanning for the source of a sound, 5 Ss were also shown to be (a) capable of localizing a single burst of noise whose duration was too brief for homing or scanning; (b) capable of using either binaural time or intensity disparities for the localization of brief tones; (c) capable of localizing a single tone-pip throughout their frequency range of hearing from 125 Hz to 8 kHz, though having considerable difficulty in their midfrequency range (1–2 kHz); and (d) capable of localizing a single brief burst of narrow band noise even in their midfrequency range. It is concluded that the capacity of pigeons to localize brief sounds and to use binaural disparity cues for doing so is not qualitatively different from that of mammals and, therefore, that the nucleus laminaris or some similar brain-stem nuclei in pigeons are probably analogous in their contribution to sound localization to the superior olivary complex in mammals. (55 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sound localization in the median sagittal plane by listeners with presbyacusis

In Experiment 1, a group of listeners with substantial hearing loss due to presbyacusis and a group of listeners with normal hearing were given three localization tests: a frontal plane test in which they judged whether sounds came from the left, overhead, or the right; a sagittal plane test in which they judged whether sounds came from directly in front, overhead, or behind; and an elevation test in which they judged the vertical position of sounds coming from in front. The two groups performed similarly on the frontal plane test, which chiefly depended upon their ability to use binaural localization cues. They performed differently on the sagittal plane and elevation tests, for which the predominant localization cues were spectral. The listeners with presbyacusis were substantially less accurate than those with normal hearing in both of these instances. They had particular difficulty judging source elevation, rarely scoring much above chance. Follow-up testing of a group of subjects in the early stages of presbyacusis showed localization performance that was intermediate to the other two groups, but far more like that of the normal-hearing listeners. In Experiment 2, additional tests were run with the following conditions designed to encourage improved performance by listeners with presbyacusic hearing loss: (1) filtering of stimuli to preclude masking of more informative high-frequency components by low frequencies; (2) simplification of the elevation test and greater spatial separation of its loudspeaker sources; and (3) use of hearing aids. Conditions 1 and 2 had no appreciable effect on performance; condition 3 significantly improved presbyacusic listeners' ability to localize in the sagittal plane, particularly when sounds came from the front.     

Sound localization in a predatory rodent, the northern grasshopper mouse (Onychomys leucogaster).

A comparison of the ability of mammals to localize sound revealed that among the animals examined to date, none of the rodents have been able to localize as accurately as the carnivores. Because all of these rodents are prey animals, the question arises as to whether their poor localization acuity is a phyletic trait of Rodentia or whether it is a trait common to prey species that may be under less selective pressure than predators to localize sound accurately. To answer this question, sound localization acuity was determined in a species that is both predatory and a rodent, the northern grasshopper mouse. Localization thresholds for a single 100-ms noise burst were determined for three grasshopper mice using a conditioned avoidance procedure. Their 50% discrimination threshold of 19° is larger than that of any of the previously tested carnivores and well within the range of other rodents. However, calculations of the binaural sound localization cues available to rodents (based on their head size) suggest that the grasshopper mouse may make more efficient use of the available locus cues than other rodents. Thus, although the grasshopper mouse cannot localize as accurately as carnivores, it appears to be more accurate than predicted for a nonpredatory rodent of its size. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Sound localization acuity in very young infants: An observer-based testing procedure": Correction.

Reports an error in the original article by B. A. Morrongiello et al (Developmental Psychology, 1990[Jan], Vol 26[1], 75–84). Corrections are made to the sentence beginning on Page 78, Column 2, Line 12 and to the text at the bottom of Page 80, Column 2, 4 lines from the bottom. (The following abstract of this article originally appeared in record 1990-11976-001.) Infants 8 to 28 weeks of age were tested to determine the smallest sound shift off midline and along the horizontal axis that could be reliably discriminated, that is, minimum audible angle. Both sound-shift and no-shift trials were presented. For each trial, an observer decided, based solely on the infant's behavior, whether the sound shifted location (i.e., an observer-based yes–no task). To isolate sensory from nonsensory factors, analyses were performed on d′ scores. The results indicated increasing localization acuity with age. The video records revealed numerous auditory orienting behaviors (e.g., alerting, quieting, and lateral head and eye movements) and highlighted the value of not requiring that specific behavioral responses be performed on sound-shift trials. Possible factors contributing to these developmental trends are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temporal Ventriloquism: Sound Modulates the Flash-Lag Effect.

Asound presented in close temporal proximity to a visual stimulus can alter the perceived temporal dimensions of the visual stimulus (temporal ventriloquism). In this article, the authors demonstrate temporal ventriloquism in the flash-lag effect (FLE), a visual illusion in which a flash appears to lag relative to a moving object. In Experiment 1, the magnitude and the variability of the FLE were reduced, relative to a silent condition, when a noise burst was synchronized with the flash. In Experiment 2, the sound was presented before, at, or after the flash (± ～100 ms), and the size of the FLE varied linearly with the delay of the sound. These findings demonstrate that an isolated sound can sharpen the temporal boundaries of a flash and attract its temporal occurrence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sound localization in an old-world fruit bat (Rousettus aegyptiacus): Acuity, use of binaural cues, and relationship to vision.

The passive sound-localization acuity of Egyptian fruit bats (Rousettus aegyptiacus) was determined using a conditioned-avoidance procedure. The mean minimum audible angle for left-right discrimination for 3 bats was 11.6°—very near the mean for terrestrial mammals. The bats also were able to localize low- and high-frequency pure tones, indicating that they can use both binaural phase-difference and binaural intensity-difference cues to localize sound. Moreover, they were able to use the binaural phase-difference cue up to at least 5.6 kHz, which is higher than other mammals yet tested. The width of the Egyptian fruit bats' field of best vision was 27°. This value is consistent with the hypothesis that the role of passive sound localization is to direct the eyes for visual scrutiny of sound sources. Thus, the passive localization abilities of these echolocating megachiropteran fruit bats do not deviate from the patterns established for nonecholocating mammals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Habituation, prepulse inhibition, fear conditioning, and drug modulation of the acoustically elicited pinna reflex in rats.

A reliable component of the acoustic startle response in animals is a flexion of the ears, the pinna reflex (PR). The present investigation attempted to develop a preparation and apparatus suitable for analyzing the PR in the awake rat. A 2nd goal was to examine the PR under behavioral and pharmacological conditions known to affect other response systems, such as whole-body startle, and determine whether the PR is a valid model for analyzing behavioral plasticity. The amplitude of the PR in 17 spinally transected male Sprague-Dawley rats was directly related to stimulus intensity and exhibited short-term habituation, prepulse inhibition, and enhancement by prior fear conditioning. PR amplitude increased following intraperitoneal administration of strychnine HCl (0.75 mg/kg) and was decreased following clonidine HCl (40 μg/kg). It is concluded that this preparation and response system are valid for studying various forms of behavioral modification. Findings are discussed in terms of the potential utility of this response system in investigating the cellular correlates of behavioral plasticity in mammals. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of oxygen inhalation on noise-induced threshold shifts in humans and chinchillas

Experiments with both humans and chinchillas indicate that the temporary threshold shift after ten-minute stimulation with 100 dB sound pressure level 1 kHz tone diminished more quickly if the subject breathed pure oxygen and it diminished even more quickly when 95% oxygen-5% carbon dioxide was inhaled rather than ambient air. This effect was observed for both poststimulatory and per-stimulatory gas inhalation.     

Sound pollution, noise pollution, and health: Community parameters.

Interviewed a random sample of 2,130 detroit, michigan and 496 los angeles, california families by telephone to explore urban parameters of noise and sound pollution. An adult member of the family reported the health status and sound-noise exposure of all family members. Results suggest (a) a possible association between sound exposure and increased prevalence of both acute and chronic illness; (b) the exposure of males to noise more frequently than females; (c) the interpretation of machine, plane, and traffic sounds as noise, and musical and children's sounds as sound; (d) the interpretation of sounds at work as noise and sounds at home as sound; and (e) the regular annoyance by sounds of approximately 1/4 of the women and 1/3 of the men in our society. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sound localization and use of binaural cues by the gerbil (Meriones unguiculatus).

Noise-localization thresholds and the ability to localize pure tones at 60° separation were determined for gerbils. The gerbils were trained using a two-choice procedure with observing response in which the gerbils made a left or right response to sounds emanating from their left or right side in order to obtain food. The average 75% correct localization threshold of 5 gerbils for a 100-ms noise burst was 27° with chance performance (p?>?.01) reached at 12°. The ability of 4 gerbils to localize both low- and high-frequency pure tones indicates that gerbils are able to use both phase- and intensity-difference locus cues. The frequency at which tone localization was poorest was 2.8 kHz, well below the theoretical frequency of ambiguity of the phase cue but within the frequency range at which phase locking declines in the mammalian auditory system. The sound localization ability of gerbils is typical of small rodents, and there is no obvious sign that it is affected by the degenerative disorder of the central auditory system which has been recently discovered in gerbils. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pitch perception in chinchillas (Chinchilla laniger): Stimulus generalization using rippled noise.

Rippled noises evoke the perception of pitch in human listeners. Infinitely iterated rippled noise (IIRN) is generated when wideband noise (WBN) is delayed, attenuated, and added to the original WBN through either a positive (+) or a negative (-) feedback loop. The pitch of IIRN[+] is matched to the reciprocal of the delay, whereas the pitch of IIRN[-] for the same delay is an octave lower. Chinchillas (Chinchilla laniger) were trained to discriminate IIRN[+] with a 4-ms delay from IIRN[+] with a 2-ms delay and then tested in a stimulus generalization paradigm with IIRN[+] at delays between 2 and 4 ms. Systematic gradients in behavioral response occurred along the dimension of delay, suggesting that a perceptual dimension corresponding to pitch exists for IIRN[+]. Behavioral responses to IIRN[-] test stimuli were more variable among chinchillas, suggesting that IIRN[-] did not evoke similar pitches relative to IIRN[+]. Systematic gradients in behavioral response were observed when IIRN[-] test stimuli were presented in the context of other IIRN[-] stimuli. Thus, other perceptual cues such as timbre may dominate the pitch cues when IIRN[-] test stimuli are presented in the context of IIRN[+] stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spectrin localization in osteoclasts: immunocytochemistry, cloning, and partial sequencing

The presence of spectrin was demonstrated in chick osteoclasts by Western blotting and light and electron microscopic immunolocalization. Additionally, screening of a chick osteoclast cDNA library revealed the presence of alpha-spectrin. Light microscope level immunocytochemical staining of osteoclasts in situ revealed spectrin staining throughout the cytoplasm with heavier staining found at the marrow-facing cell margin and around the nuclei. Confocal microscopy of isolated osteoclasts plated onto a glass substrate showed that spectrin encircled the organelle-rich cell center. Nuclei and cytoplasmic inclusions were also stained and the plasma membrane was stained in a nonuniform, patchy distribution corresponding to regions of apparent membrane ruffling. Ultracytochemical localization showed spectrin to be found at the plasma membrane and distributed throughout the cytoplasm with especially intense staining of the nuclear membrane and filaments within the nuclear compartment.     

New growth of axons in the cochlear nucleus of adult chinchillas after acoustic trauma

This study determined the effect of acoustic overstimulation of the adult cochlea on axons in the cochlear nucleus. Chinchillas were exposed to an octave-band noise centered at 4 kHz at 108 dB sound pressure level for 1.75 h. One chinchilla was never exposed to the noise, and several others had one ear protected by an ear plug or prior removal of the malleus and incus. Exposure of unprotected ears caused loss of inner and outer hair cells and myelinated nerve fibers, mostly in the basal half of the cochlea. Cochlear nerve fiber degeneration, ipsilateral to the exposed ears, was traced to regions of the cochlear nucleus representing the damaged parts of the cochlea. In silver impregnations of a deafferented zone in the posteroventral cochlear nucleus, the concentration of axons decreased by 43% after 1 month and by 54% after 2 months. However, by 8 months, the concentration of thinner axons, with diameters of less than 0.46 microm, increased by 46-90% over that at 2 months. The concentration of axons with larger diameters did not change. Between 2 and 8 months small axonal endings appeared next to neuronal cell bodies. This later increase of thinner axons and endings is consistent with a reactive growth of new axons of relatively small diameter. The emergence of small perisomatic boutons suggests that the new axons formed synaptic endings, which might contribute to an abnormal reorganization of the central auditory system and to the pathological changes that accompany acoustic overstimulation.     

Sound stimuli and following in a domestic fowl: Frequency, rate, and duration.

Notes that repetitive taps or tones elicit strong following in the young of domestic fowl. The relations between the physical properties of such sounds, including pure tone frequency, rate, and duration were studied in 5 experiments with White Leghorn chicks. When tone characteristics were varied simultaneously, an optimal duration (i.e.,     

Effects of inner hair cell loss on inferior colliculus evoked potential thresholds, amplitudes and forward masking functions in chinchillas

The effects of outer hair cell (OHC) loss on evoked potential (EVP) thresholds, amplitudes and forward masking (FWM) functions have been fairly well characterized. In contrast, the effects of inner hair cell (IHC) losses are largely unknown, primarily due to the difficulty of producing selective IHC lesions. Recent studies have shown that IHCs of the chinchilla are preferentially damaged by the anticancer drug, carboplatin. In this study, we administered a single 100 mg/kg dose of carboplatin to four chinchillas, to examine the effects of IHC lesions on EVPs measured from the inferior colliculus (IC-EVPs). Thresholds and amplitude functions were measured for 0.25-16 kHz tone bursts, and FWM functions were measured at 1, 2 and 4 kHz, using masker probe intervals of 2, 5, 10, 20, 40 and 80 ms, before and 1-2 months after carboplatin treatment. Histology revealed IHC lesions ranging from approximately 15 to 90%, with virtually no loss of OHCs. Surprisingly, even massive IHC lesions were not associated with elevations of IC-EVP thresholds. IC-EVP amplitudes at suprathreshold levels were sometimes depressed, sometimes enhanced, and in some cases unchanged. IHC lesions increased susceptibility to FWM, particularly at intermediate (10-20 ms) masker-probe intervals, without significantly changing the overall time course of FWM. The results provide new perspectives on the contribution of IHCs to FWM, and on the ability of the central auditory system to adapt to a significant reduction of neural input from the cochlea.     

Use of computed tomography to investigate cheek tooth abnormalities in chinchillas (Chinchilla laniger)

Computerised tomographic scanning was used to investigate tooth structure in chinchillas (Chinchilla laniger), both cheek tooth crown and root abnormalities being common in this species. This paper describes a common form of dental disease affecting species with continuously growing teeth, with particular reference to the chinchilla, and confirms the potential role of computed tomography (CT) in its early diagnosis. CT imaging is compared with previously available methods of investigation which frequently fail to detect early pathological changes.     

机上冷却烧结机对机尾除尘系统的影响

通过对包钢炼铁厂二烧车间工艺改造后的生产实践和测试数据作分析讨论,说明机上冷却工艺有利于除尘系统的正常工作,有利于简化除尘设备改善环境;是烧结行业保护环境的发展方向.