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PubMed2004

Simulation study of effects of speed of sound and attenuation on ultrasound lateral resolution.

Experiments have shown that the lateral profile of a point target measured with a clinical ultrasound scanner is wider when the target is embedded in a urethane phantom than when it is in a traditional gel phantom. The behavior has been attributed to the low speed of sound in the urethane material, with the possibility that some of the broadening is caused by increased attenuation in this material. In this paper we apply a computer simulation model to study this behavior. Lateral beam profiles modeled for targets within a medium having a speed of sound and an attenuation matching that of urethane are compared with profiles for targets in a water-based gel. Simulations yield results that agree qualitatively with published experimental results. The lateral profile broadening in urethane is caused by the 6 % mismatch between speed of sound in this material and the speed of sound assumed in the receive focusing and beam forming. Attenuation plays a lesser role than the mismatch of the speed of sound.

Algorithms↗
PubMed1997

Maternal perception of sound-provoked fetal movement in the early intrapartum period.

OBJECTIVE: To determine the relationship between maternal perception of sound-provoked fetal movement in the early intrapartum period and perinatal outcome. METHOD: 739 singleton pregnant women of at least 32 weeks gestation who were admitted to the labor ward, underwent the maternal perception of sound-provoked fetal movement test. All were in the latent phase of labor with singleton cephalic presentation. The result of maternal perception of sound-provoked fetal movement was compared with the perinatal outcome using sensitivity, specificity, negative predictive value, positive predictive value and accuracy. RESULTS: When 739 pregnant women were compared to the perinatal outcome, maternal perception of sound-provoked fetal movement had sensitivity 100%, specificity 98.9%, positive predictive value 15.1%, negative predictive value 100%, and accuracy 90.1%. CONCLUSION: The finding suggested the usefulness of maternal perception of sound-provoked fetal movement as an effective screening test to identify fetuses at risk in the early intrapartum period because of its high sensitivity and specificity. This is a simple and inexpensive test for evaluating fetal well-being in a primary health care setting.

Acoustic Stimulation↗
PubMed2002

Effect of sex steroids and coital experience on ferrets' preference for the smell, sight and sound of conspecifics.

Previous research showed that ferrets of both sexes recognize potential opposite-sex mates on the basis of volatile body odors. We compared the ability of estrogen and androgen treatments to activate a preference in gonadectomized male and female ferrets for distal cues (volatile body odors alone or volatile odors+sight+sounds) from male versus female stimulus ferrets using an airtight Y-maze and a "stimulus proximity" or a "discrete trials" testing paradigm. Sexually naive, gonadectomized male and female ferrets that received either testosterone propionate (TP) or estradiol benzoate (EB) spent equal time in proximity to goal boxes that provided either volatile odors alone or odors+sight+sounds of male and female stimulus animals. After they received coital experience, male and female subjects (treated with either EB or TP) showed a significant preference for both types of opposite-sex stimuli. When discrete trials tests were given to these ferrets prior to receiving coital experience, EB-treated females preferred to approach odor only cues, as well as odors+sight+sounds of stimulus males, and this preference was further strengthened after coital experience. Sexually naive, TP-treated males preferred to approach volatile odor cues from stimulus females; however, these animals showed an equal preference for odors+sight+sounds of stimulus females and males. Again, after coital experience, males' preference for both sets of cues from stimulus females was significantly enhanced. Thus, in sexually naive ferrets, discrete trials, but not stimulus proximity tests, revealed a preference for distal cues (body odors with or without concurrent sight and sounds) from opposite-sex conspecifics in subjects of both sexes. Coital experience significantly enhanced these preferences for heterosexual distal cues under both testing paradigms.

Animal Communication↗
PubMed2000

Collinear acousto-optic diffraction using two nearby sound frequencies

Collinear acousto-optic spectrometers with sound consisting of one frequency have a spectral transfer function with many good characteristics, such as a narrow bandwidth, ... the side lobes, however, are rather high. To reduce these side lobes, one can try to apodize the sound in the acousto-optic cell by using a sound wave consisting out of two frequencies. At certain times, this produces a more smoothened sound field in the cell than in the one-frequency case. The resulting transfer function will contain lower side lobes. Also, the influence of all the sound field parameters--the amplitude, frequency difference, and time--on the transmission function is studied. Out of these results, better-performing collinear spectrometers can be designed.

Journal Article↗
PubMed1997

Pre-attentive processing of spectrally complex sounds with asynchronous onsets: an event-related potential study with human subjects.

Neuronal mechanisms involved in the processing of complex sounds with asynchronous onsets were studied in reading subjects. The sound onset asynchrony (SOA) between the leading partial and the remaining complex tone was varied between 0 and 360 ms. Infrequently occurring deviant sounds (in which one out of 10 harmonics was different in pitch relative to the frequently occurring standard sound) elicited the mismatch negativity (MMN), a change-specific cortical event-related potential (ERP) component. This indicates that the pitch of standard stimuli had been pre-attentively coded by sensory-memory traces. Moreover, when the complex-tone onset fell within temporal integration window initiated by the leading-partial onset, the deviants elicited the N2b component. This indexes that involuntary attention switch towards the sound change occurred. In summary, the present results support the existence of pre-perceptual integration mechanism of 100-200 ms duration and emphasize its importance in switching attention towards the stimulus change.

Adolescent↗
PubMed2003

The sound-level-dependent growth in the extent of fMRI activation in Heschl's gyrus is different for low- and high-frequency tones.

fMRI (functional magnetic resonance imaging) was used to investigate whether the growth in activation of the human auditory cortex, with increasing sound level, is discernibly different for high- and low-frequency tones. Ten volunteers were scanned whilst listening to sequences of low-frequency (0.30-kHz) tones at sound levels between 42 and 96 dB sound pressure level (SPL), and 10 whilst listening to high-frequency (4.75-kHz) tones at the same sound levels. Activation was measured in Heschl's gyrus (including primary auditory cortex) which has been shown to be most sensitive to changes in sound level. For the 0.30-kHz tone, the extent of activation was flat up to 66 dB and then showed a rapid growth which continued up to the highest level studied (96 dB SPL). In contrast, increasing the level of 4.75-kHz tones produced a steady growth in the extent of activation across the range of levels studied. These results are consistent with physiological evidence suggesting that recruitment of primary auditory cortical neurones may be different at high and low frequencies.

Acoustic Stimulation↗
PubMed2004

A physiological correlate for the intolerance to both internal and external sounds.

The notion that stress can induce chronic tinnitus, or increase its intensity, is predominant in the literature on tinnitus. However, there is little empirical support for this claim, since previous studies rely merely on subjective reports. In the present study, we used an objective physiological measure of stress (i.e., basal secretion of the stress hormone cortisol), in order to assess the relationship between tinnitus and stress. We hypothesized that tinnitus, a permanent internal sound, should behave as a stressor and should be accompanied by chronically elevated cortisol levels in individuals with severe tinnitus. In addition, we hypothesized that suffering from severe tinnitus should generalize to an intolerance towards external sounds. Two groups each comprised of 18 participants (with and without tinnitus) matched on education and health status participated in the study. Tinnitus severity, as assessed by tinnitus-related distress, was high in half of the tinnitus participants, and low in the other half. Basal cortisol levels were measured using saliva samples (five saliva samples per day for 3 days within a week) taken in the participant's natural environment. Intolerance to external sounds was assessed psychometrically. The high tinnitus-related distress group had chronic cortisol levels greater than both the low tinnitus-related distress and control groups, and also displayed greater intolerance to external sounds. The low tinnitus-related distress and control groups did not differ from each other on either of these measures. Our study thus provides the first physiological and empirical evidence of a link between intolerance to both internal (tinnitus) and external sounds in persons with tinnitus, and is compatible with the clinical observation that severe tinnitus is associated with high stress levels.

Aged↗
PubMed1999

Sound duration selectivity in the pallid bat inferior colliculus.

Neurons selective for sound duration have been reported in the auditory midbrain and cortex of several specialized vertebrate species that process behaviorally relevant signals of stereotypic duration. This study examines duration selectivity in the inferior colliculus (IC) of the pallid bat to determine if this selectivity is limited to regions that serve echolocation, or if it extends to low-frequency regions that serve passive listening. It also focuses on the temporal response properties of duration-selective neurons to elucidate mechanisms that may underlie the creation of this selectivity. Of 140 neurons tested, 36% were selective for short durations of </=7 ms, and acted as short-pass or bandpass duration filters. Sixteen percent, termed long duration neurons, differed in that they required minimum sound durations of 5-50 ms before responding, and all acted as long-pass duration filters. Short duration neurons were equally common in the high-frequency region serving echolocation and the lateral low-frequency region that serves passive listening, indicating that selectivity for short duration sounds was not associated only with the specialized function of echolocation. Long duration neurons were most common in the medial low-frequency region IC. Selectivity for short and long duration sounds was therefore not uniformly distributed across the IC. Analyses of the temporal response properties of short duration neurons, and the application of bicuculline to block gamma-aminobutyric acid-A receptors, were used to infer the synaptic interactions that underlie the creation of duration selectivity, the role of inhibition in its creation, and whether a coincidence mechanism proposed by Casseday et al. (Science 264 (1994) 847-850) is consistent with the behavior of the duration-selective neurons recorded in the pallid bat IC. Present results suggest that while some neurons do behave in a manner that is consistent with the coincidence mechanism, the behaviors of others suggest that more than one mechanism may create a selectivity for short duration sounds.

Animals↗
PubMed2002

Effect of prenatal sound stimulation on medio-rostral neostriatum/hyperstriatum ventrale region of chick forebrain: a morphometric and immunohistochemical study.

The higher auditory association area in chick forebrain, i.e. medio-rostral neostriatum/hyperstriatum ventrale region (MNH), is involved in juvenile auditory filial imprinting. Studies show that neuronal size as well as expression of calcium-binding proteins, parvalbumin (PV) and calbindin D28K (CaBP) are regulated by neuronal activation. In the present study, we have determined the effect of extra auditory stimulation, given as a prenatal sound enrichment protocol, on MNH neurons of posthatch day 1 chicks. Patterned species-specific or musical (sitar) sounds were provided in a graded manner from embryonic day 10 through hatching. Thionin and immunohistochemically stained (PV and CaBP) neurons were evaluated by morphometric methods. The thionin-stained MNH neurons of both the auditory stimulated groups showed a significant increase in nuclear area compared to controls. The change in nuclear dimension was greater in the music-stimulated than in the species-specific sounds-stimulated group. These observations indicate a positive influence of prenatal sound stimulation on MNH neurons. The auditory stimulated groups also demonstrated an increase in the proportion of PV- and CaBP-neurons compared to controls, with the species-specific sounds-stimulated group showing a significantly higher percentage of immunostained cells than the music-stimulated group. However, immunostained cells of both the auditory stimulated groups did not show a significant change in size. These cytoplasmic proteins, by acting as intracellular buffers, enable neurons to display high electrical activity without calcium overload. The influx of Ca(2+) ions is essential for long-term potentiation, a phenomenon important for learning and memory. The increase in percentage of the neurons containing calcium-binding proteins may provide a morphological basis for enhancement of auditory imprinting and learning.

Acoustic Stimulation↗
PubMed1996

Sound level variation findings for pianissimo and fortissimo phonations in repeated measurements.

Ten vocally untrained female university students vocalized /a:/ at five given pitches within the average female speaking range (196, 220, 262, 330, and 396 Hz) as softly as possible (pianissimo) and as loudly as musically acceptable (fortissimo). To study the repeatability of voice range profile (sound level) measurement, the procedure was repeated 10 times in each of the five sample sessions during the day, in connection with vocal loading that included five oral readings (45 min each), 15-min pauses, and a lunch break (45 min). A sound level meter specially designed for voice range profile measurement was used. The effect of the loading was seen on the mean sound level changes and intraindividual variation on SDs. The difference between the first phonation and best performance indicates significance of the repetition of the measurement. The sound level averaged across the pitches rose significantly during loading. The intraindividual SD varied between 3 and 4 dBA according to pitch and loudness, and the sound level difference between the first phonation and best performance was approximately 5 dBA in pianissimo and approximately 7 dBA in fortissimo.

Adult↗
PubMed2000

Perception of complex sounds: N1 latency codes pitch and topography codes spectra.

OBJECTIVES: This work aimed to find out whether the human cortical 'tonotopy' represents the true fundamental frequency (Fo) of complex sounds, or the center frequency CF at which harmonics peak in the audio spectrum. Indeed, complex periodic sounds (such as those of the human voice, musical instruments, etc.) comprise a 'fundamental component' (Fo) and its 'harmonics' (2Fo, 3Fo, ...nFo). These often peak around a certain frequency CF. As Fo and CF are confounded in pure (sinusoidal) tones, the question of whether Fo or CF is represented through tonotopy had been hitherto unresolved. METHODS: Whole-head recordings of brain electrical activity were obtained for 16 subjects submitted to an array of 9 different series of sounds (3 Fox3 CF). Electrophysiological data were analyzed separately for each sound and each subject with brain functional imaging and dipole reconstruction. RESULTS: Equivalent dipole sources of N1 components were, significantly for all subjects, more and more frontally oriented as CF increased, independently of Fo. CONCLUSIONS: Sounds are mapped in both the right and the left primary auditory cortices according to the spectral profiles of their harmonics (CF), rather than their fundamental frequencies (Fo).

Adult↗
PubMed2001

Parental reports of 'MAMA' sounds in infants: an exploratory study.

This study investigated the use of 'mama' or similar sounds (collectively referred to as 'MAMA') by 75 infants less than six months of age. Parents were directed to listen for 'MAMA' sounds and to note the sounds made, the age of onset, whether the sounds appeared to be directed to any person or persons and whether they appeared to have a purpose. 'MAMA' began at a mode of two months, range two weeks to five months, was usually part of a cry, and was always interpreted as a 'wanting' sound. Most parents thought that the infant wanted some form of attention, but a minority thought it indicated hunger. Responses to a Structured Response Protocol indicated that some infants uttering 'MAMA' were satisfied if a favourite caretaker approached and paid attention to them while the remainder were satisfied if they were both paid attention to and picked up. The 'MAMA' cry appears to promote attention-giving behaviour by parents and other caretakers.

Child Language↗
PubMed2002

Thresholds of discomfort for complex stimuli: acoustic and sound-quality predictors.

The purpose of this study was to explain differences in threshold of discomfort (TD) across complex stimuli using acoustic and sound-quality variables as predictors. Two 4-tone complexes and 10 environmental sounds were used as stimuli. The environmental sounds consisted of a baby crying, hairdryer blowing, glass breaking, jet engine propelling, person laughing, motorcycle accelerating, orchestra tuning, telephone ringing, siren blowing, and toilet flushing. One-third octave band (1/3 OB) spectra were obtained for the 12 stimuli, with overall rms amplitude held constant across the stimuli. Nine acoustic quantities describing the high- and low-frequency content, peakiness, and bandwidth of each 1/3 OB spectrum were defined. Twenty adult subjects, 6 men and 14 women, with normal hearing sensitivity participated in the study. TDs were obtained from each subject for all of the stimuli. In addition, subjects rated each of the stimuli for annoyance, harshness, loudness, noisiness, and tinniness on a 10-point scale. These ratings were completed at a level 10 dB below each subjects TD for that stimulus. A hierarchical multiple regression analysis was used to estimate the amount of variance in TDs accounted for by subject differences, defined acoustic properties, and sound-quality ratings. Results indicated that, after controlling for intersubject differences, acoustic and sound-quality factors significantly influenced TD ratings. Increases in high-frequency cutoff and low-frequency cutoff, as well as higher ratings of loudness and annoyance, were associated with higher TDs. Associated with lower TDs were an increase in the frequency of the primary spectral peak, an increase in the number of spectral peaks, an increase in the center frequency, an increase in the area under the frequency response curve 30 dB down from the peak amplitude, an increase in the calculated loudness level re ANSI S3.4-1980, and higher ratings of tinniness.

Acoustics↗
PubMed1998

Effects of treatment for sound errors in apraxia of speech and aphasia.

This investigation was designed to examine the acquisition, generalization, and maintenance effects of a treatment for sound errors in speakers with co-occurring apraxia of speech and aphasia. Three speakers with chronic apraxia of speech and aphasia were studied in the context of a multiple baseline design across speakers and behaviors. Treatment combined the use of minimal contrast pairs with traditional sound production training techniques such as integral stimulation and articulatory placement cueing and was applied sequentially to sounds that were determined to be consistently in error before training. Results revealed increased correct sound productions for all speakers in trained and untrained words. Response generalization effects across sounds and stimulus generalization effects varied, but appeared to be limited for most speakers. Although positive maintenance effects were evidenced, some loss of treatment gains was noted following cessation of treatment.

Apraxias↗
PubMed2001

Use of the flexion test of the distal forelimb in the sound horse: repeatability and effect of age, gender, weight, height and fetlock joint range of motion.

The flexion test of the distal limb is a commonly used clinical tool in both lame and sound horses. In the latter use it is given some predictive value. In recent studies it has been shown that examiner-related factors (force, time) may strongly influence the outcome of the test. In the present study, the possible influences of a number of horse-related factors and short- and long-term repeatability were investigated. Flexion tests were performed by the same researcher in 100 clinically sound horses under standardized conditions. The outcome of the test was scored on a 9-point semiquantitative scale. The maximum flexion angles of the fetlock joints were measured and the range of motion (ROM) of the fetlock joint was calculated. In the second part of the study, flexion tests were repeated, at intervals of 10 min, 30 min, 48 h and 6 months in 23 horses to assess repeatability. Over 60% of the 100 sound horses had a positive flexion test. Of these, about 50% showed a slight lameness, 35% a mild lameness, and 15% a distinct lameness. There was no influence of weight, height or ROM on the score of the flexion test. The outcome of the flexion test increased significantly with age and was significantly higher in mares than in geldings. When repeating the flexion test with short intervals of 10 and 30 min, the score increased significantly after the second test. Repeated flexion after 48 h did not result in a significantly different outcome. Over a 6-month period, the outcome of the test decreased significantly and the ROM increased significantly. It is concluded that most clinically sound horses have a (slightly) positive flexion test of the distal limb. This and the lack of long-term consistency of the test cast doubt on the presumption that a positive flexion test may be an indication for subclinical joint disorders and question the possible value of the test as a predictor of future joint-related problems. There exists a wide individual variation in ROM of the fetlock joint with, in sound horses, no relationship between ROM and the outcome of the flexion test. The factors age and gender should be taken into account when interpreting the results of a flexion test.

Age Factors↗
PubMed2005

Synchronizing to real events: subjective audiovisual alignment scales with perceived auditory depth and speed of sound.

Because of the slow speed of sound relative to light, acoustic and visual signals from a distant event often will be received asynchronously. Here, using acoustic signals with a robust cue to sound source distance, we show that judgments of perceived temporal alignment with a visual marker depend on the depth simulated in the acoustic signal. For distant sounds, a large delay of sound relative to vision is required for the signals to be perceived as temporally aligned. For nearer sources, the time lag corresponding to audiovisual alignment is smaller and scales at rate approximating the speed of sound. Thus, when robust cues to auditory distance are present, the brain can synchronize disparate audiovisual signals to external events despite considerable differences in time of arrival at the perceiver. This ability is functionally important as it allows auditory and visual signals to be synchronized to the external event that caused them.

Auditory Perception↗
PubMed2001

Ecosystem impacts of three sequential hurricanes (Dennis, Floyd, and Irene) on the United States' largest lagoonal estuary, Pamlico Sound, NC.

Three sequential hurricanes, Dennis, Floyd, and Irene, affected coastal North Carolina in September and October 1999. These hurricanes inundated the region with up to 1 m of rainfall, causing 50- to 500-year flooding in the watershed of the Pamlico Sound, the largest lagoonal estuary in the United States and a key West Atlantic fisheries nursery. We investigated the ecosystem-level impacts on and responses of the Sound to the floodwater discharge. Floodwaters displaced three-fourths of the volume of the Sound, depressed salinity by a similar amount, and delivered at least half of the typical annual nitrogen load to this nitrogen-sensitive ecosystem. Organic carbon concentrations in floodwaters entering Pamlico Sound via a major tributary (the Neuse River Estuary) were at least 2-fold higher than concentrations under prefloodwater conditions. A cascading set of physical, chemical, and ecological impacts followed, including strong vertical stratification, bottom water hypoxia, a sustained increase in algal biomass, displacement of many marine organisms, and a rise in fish disease. Because of the Sound's long residence time ( approximately 1 year), we hypothesize that the effects of the short-term nutrient enrichment could prove to be multiannual. A predicted increase in the frequency of hurricane activity over the next few decades may cause longer-term biogeochemical and trophic changes in this and other estuarine and coastal habitats.

Animals↗
PubMed1997

Representation of sound localization cues in the auditory thalamus of the barn owl.

Barn owls can localize a sound source using either the map of auditory space contained in the optic tectum or the auditory forebrain. The auditory thalamus, nucleus ovoidalis (N.Ov), is situated between these two auditory areas, and its inactivation precludes the use of the auditory forebrain for sound localization. We examined the sources of inputs to the N.Ov as well as their patterns of termination within the nucleus. We also examined the response of single neurons within the N.Ov to tonal stimuli and sound localization cues. Afferents to the N.Ov originated with a diffuse population of neurons located bilaterally within the lateral shell, core, and medial shell subdivisions of the central nucleus of the inferior colliculus. Additional afferent input originated from the ipsilateral ventral nucleus of the lateral lemniscus. No afferent input was provided to the N.Ov from the external nucleus of the inferior colliculus or the optic tectum. The N.Ov was tonotopically organized with high frequencies represented dorsally and low frequencies ventrally. Although neurons in the N.Ov responded to localization cues, there was no apparent topographic mapping of these cues within the nucleus, in contrast to the tectal pathway. However, nearly all possible types of binaural response to sound localization cues were represented. These findings suggest that in the thalamo-telencephalic auditory pathway, sound localization is subserved by a nontopographic representation of auditory space.

Acoustic Stimulation↗