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At least 721 records · Page 40Linked to original sources
PubMed2006

Sound speed correction in ultrasound imaging.

A constant sound speed of 1.54 mm/micros is generally used by ultrasound imaging systems for delay and timing. However, the body's sound speed in-homogeneity can lead to defocusing and increased clutter. To provide an improvement using standard transducers, the sound speed used in delay and timing was computed using different sound speeds. We observed improvement in lateral resolution and clutter in phantom, OB, abdominal, and breast imaging. In OB and abdominal imaging using a 4 MHz curved array, 1.48 mm/micros provided higher image quality in many situations. In breast with an 8 MHz linear array, 1.44 mm/micros provided better images in some cases. To provide an automated way to determine and adjust the sound speed used by the imaging system, an algorithm was developed that determines the sound speed that produces the best overall lateral image quality by analyzing the spatial frequency content in a single B-mode frame of channel data using images reconstructed using various trial sound speeds. The metric produced correlates well with the observed best lateral image quality.

Algorithms↗
PubMed2000

Dependence of sonochemical luminescence on various sound fields

To understand the effect of the sound field on sonochemical luminescence, the exact sound pressure must be determined in each field. In this study it was determined by the Shlieren method, which measures the sound pressure without mixing the sound fields. We compared the efficiency of the sonochemical luminescence in three different ways: changing the diameter of the transducer, combining two transducers to obtain crossed propagating directions and surrounding the sound field by a glass cylinder. In the last case cylinders with various sizes were studied. We found that (i) at the same sound pressure, the larger transducer induces stronger luminescence per unit volume, (ii) driving two transducers produces stronger luminescence than the sum of each transducer and (iii) a glass cylinder surrounding the sound field induces stronger luminescence.

Journal Article↗
PubMed2003

High-frequency sound transmissions under water and risk of decompression sickness.

We tested the possible occurrence of a neurological insult secondary to high-frequency sound exposure. Immersed, anesthetized rats were subjected to a simulated diving profile designed to induce decompression sickness, while exposed to the transmission of an acoustic beacon. Intermittent sound at a pressure level of 184.5 dB re 1 microPa at 1 m (1.7 kPa), a frequency of 37 kHz, and with a duration of 4 ms, was transmitted in a duty cycle of 0.26%. Four groups, each containing nine animals, were included in the study as follows: group 1, immersion only, no sound exposure; group 2, immersion with sound exposure; group 3, diving simulation when immersed, no sound exposure; group 4, diving simulation when immersed, with sound exposure. Somatosensory evoked potentials (SSEPs) were recorded the day before the study, and a second recording was made 30 min after immersion. Some of the SSEP components disappeared after the dive in 3 rats from group 3 and 2 rats from group 4. SSEP components could not be identified in a significantly larger number of animals from groups 3 and 4, compared with groups 1 and 2. No differences were found in wave latency, amplitude or conduction time. Our data show that the high-frequency sound exposure employed did not contribute to the development of the neurological insult.

Animals↗
PubMed2000

Hemispheric lateralization in an analysis of speech sounds. Left hemisphere dominance replicated in Japanese subjects.

Evoked magnetic responses to speech sounds [R. Näätänen, A. Lehtokoski, M. Lennes, M. Cheour, M. Huotilainen, A. Iivonen, M. Vainio, P. Alku, R.J. Ilmoniemi, A. Luuk, J. Allik, J. Sinkkonen and K. Alho, Language-specific phoneme representations revealed by electric and magnetic brain responses. Nature, 385 (1997) 432-434.] were recorded from 13 Japanese subjects (right-handed). Infrequently presented vowels ([o]) among repetitive vowels ([e]) elicited the magnetic counterpart of mismatch negativity, MMNm (Bilateral, nine subjects; Left hemisphere alone, three subjects; Right hemisphere alone, one subject). The estimated source of the MMNm was stronger in the left than in the right auditory cortex. The sources were located posteriorly in the left than in the right auditory cortex. These findings are consistent with the results obtained in Finnish [R. Näätänen, A. Lehtokoski, M. Lennes, M. Cheour, M. Huotilainen, A. Iivonen, M.Vainio, P.Alku, R.J. Ilmoniemi, A. Luuk, J. Allik, J. Sinkkonen and K. Alho, Language-specific phoneme representations revealed by electric and magnetic brain responses. Nature, 385 (1997) 432-434.][T. Rinne, K. Alho, P. Alku, M. Holi, J. Sinkkonen, J. Virtanen, O. Bertrand and R. Näätänen, Analysis of speech sounds is left-hemisphere predominant at 100-150 ms after sound onset. Neuroreport, 10 (1999) 1113-1117.] and English [K. Alho, J.F. Connolly, M. Cheour, A. Lehtokoski, M. Huotilainen, J. Virtanen, R. Aulanko and R.J. Ilmoniemi, Hemispheric lateralization in preattentive processing of speech sounds. Neurosci. Lett., 258 (1998) 9-12.] subjects. Instead of the P1m observed in Finnish [M. Tervaniemi, A. Kujala, K. Alho, J. Virtanen, R.J. Ilmoniemi and R. Näätänen, Functional specialization of the human auditory cortex in processing phonetic and musical sounds: A magnetoencephalographic (MEG) study. Neuroimage, 9 (1999) 330-336.] and English [K. Alho, J. F. Connolly, M. Cheour, A. Lehtokoski, M. Huotilainen, J. Virtanen, R. Aulanko and R.J. Ilmoniemi, Hemispheric lateralization in preattentive processing of speech sounds. Neurosci. Lett., 258 (1998) 9-12.] subjects, prior to the MMNm, M60, was elicited by both rare and frequent sounds. Both MMNm and M60 sources were posteriorly located in the left than the right hemisphere.

Adult↗
PubMed2006

Can the speed of sound be used for detecting critical states of fluid mixtures?

The phenomenology of sound speeds in fluid mixtures is examined near and across critical lines. Using literature data for binary and ternary mixtures, it is shown that the ultrasound speed along an isotherm-isopleth passes through a minimum value in the form of an angular (or V-shaped) point at critical states. The relation between critical and pseudo-critical coordinates is discussed. For nonazeotropic fixed-composition fluid mixtures, pseudo-critical temperatures and pressures are found to be lower than the corresponding critical temperatures and pressures. The analysis shows that unstable pseudo-critical states cannot be detected using acoustic methods. The thermodynamic link between sound speeds and isochoric heat capacities is formulated and discussed in terms of p-Vm-T derivatives capable of being calculated using cubic equations of state. Based on the Griffiths-Wheeler theory of critical phenomena, a new specific link between critical sound speeds and critical isochoric heat capacities is deduced in terms of the rate of change of critical pressures and critical temperatures along the p-T projection of the critical locus of binary fluid mixtures. It is shown that the latter link can be used to obtain estimates of critical isochoric heat capacities from the experimental determination of critical speeds of sound. The applicability domain of the new link does not include binary systems at compositions along the critical line for which the rate of change in pressure with temperature changes sign. The new equation is combined with thermodynamic data to provide approximate numerical estimates for the speed of sound in two mixtures of carbon dioxide and ethane at different temperatures along their critical isochores. A clear decrease in the sound speed is found at critical points. A similar behavior is suggested by available critical heat capacity data for several binary fluid mixtures. Using an acoustic technique, the critical temperature and pressure were determined for three different mixtures of methane and propane, and compared with literature data obtained using conventional methods. It is concluded that acoustic-based techniques are reliable to determine, for the most part, critical surfaces of fluid mixtures. The remaining few cases where the present analysis cannot be applied could be tested by the thermodynamic calculation of critical sound speeds using crossover equations of state in conjunction with experimentally determined critical isochoric heat capacities.

Journal Article↗
PubMedDate not supplied

Contribution of heating, ventilation, and air conditioning airflow and conversation to the ambient sound in a neonatal intensive care unit.

Sound reduction strategies in the neonatal intensive care unit (NICU) must focus on the sources of excessive sound. We studied the relative contribution of personnel conversation and heating, ventilation, and air conditioning (HVAC) airflow by measuring several parameters of sound during four environmental conditions: unaltered ambient sound, HVAC airflow off, HVAC airflow and conversation off, and conversation off. All measurements were decreased by interrupting HVAC airflow and conversation. The reduction was greater when conversation was stopped. The method of sound reduction did not change the frequency distribution of sound. Attention to personnel conversation may be effective in lowering sound exposure in the NICU. The contribution of HVAC airflow should be measured in new constructions and renovations.

Air Conditioning↗
PubMed1981

Systematic sound preference asa characteristic of phonological disability.

Systematic sound preference was described as a common phonological process seen in young children with unintelligible speech. In its classic form, sound preference occurred when an entire class of sounds was replaced by one sound. Sound preference most commonly occurred in the word-initial position and affected fricatives more frequently than any other manner category. In cases where sound preference did not affect all members of a manner of production, it affected the voiceless and/or non-labial sounds.

Child, Preschool↗
PubMed1987

Electroacoustic calibration for sound field warble tone thresholds.

Walker, Dillon, and Byrne (1984) suggested reference equivalent threshold sound pressure levels (RETSPLs) for warble tones with specific modulation parameter values audited from a test position at the critical distance in a semireverberant sound field. This study evaluated these RETSPLs in two typical audiometric rooms and with typically encountered FM tones. Thresholds were measured under earphones and in two sound fields for 6-11 normal hearers at six test frequencies. Results indicated that there was a small but statistically significant difference between earphone and sound field thresholds in 4 of 24 comparisons. However, in both sound fields, 99% of the sound field thresholds were within 10 dB of the earphone thresholds. It is concluded that these RETSPLs are appropriate for electroacoustic calibration of sound field warble tones similar to those used in this study.

Acoustic Stimulation↗
PubMed1977

Visual lung-sound characterization by time-expanded wave-form analysis.

To characterize lung sounds objectively, we examined, by means of time-amplitude plots, selected tape recordings of auscultatory phenomena considered by six observers to be typical of those in a standard classification. Normal lung sounds could not consistently be visually distinguished from adventitious sounds at conventional chart recorder speeds of 100 mm per second or less, but the differentiation was easily achieved when the time scale of the plots was raised to 800 mm per second. When discontinuous sounds (rales, crackles or crepitations) were heard clinically, the time-expanded wave forms showed intermittent "discontinuous" deflections usually less than 10 msec in duration. When continuous sounds (rhonchi or wheezes) were heard, the deflections were usually more than 250 msec. Time-expanded wave form analysis provides reproducible visual displays that allow documentation of the differentiating features of lung sounds and enhances the diagnostic utility of the sounds.

Auscultation↗
PubMed2006

Nonlinear auditory mechanism enhances female sounds for male mosquitoes.

Sound plays an important role in the life history of mosquitoes. Male mosquitoes detect females by the sound generated by their wingbeat. Because female wings are weak acoustic radiators, males have been driven by sexual selection to evolve sensitive acoustic sensors. Mosquito antennae are very sensitive acoustic receivers, featuring up to 16,000 sensory cells, a number comparable with that contained in the human cochlea. The antennal sound receiver exhibits frequency selectivity, input amplification, and self-generated oscillations, features that parallel the functional sophistication of the cochlear amplifier. Although arguably the male antenna is well suited to receiving weak female sounds, the role of active mechanisms in mosquito hearing is far from understood. Previous mechanical studies on mosquito hearing largely focused on the steady-state antennal response to harmonic sounds, mostly evaluating the data through conventional Fourier transforms. Here, we report on the time-resolved mechanical behavior of the male antenna in response to female sounds. Crucially, stimuli were designed to reflect the temporal acoustic profile of a female flying by. With these stimuli, several previously unreported nonlinear features were unveiled, involving amplification, compression, and hysteresis. The time-resolved analysis reveals that, through the active participation of the sensory neurons, the antenna mechanically responds to enlarge its own range of detection. This behavior augments the capacity of the antennal receiver to detect female sounds, enhancing the male's chance to successfully pursue a passing female.

Acoustics↗
PubMed2002

Precognitive and cognitive elements in sound localization.

Sound localization behavior is of great importance for an animal's survival. To localize a sound, animals have to detect a sound source and assign a location to it. In this review we discuss recent results on the underlying mechanisms and on modulatory influences in the barn owl, an auditory specialist with very well developed capabilities to localize sound. Information processing in the barn owl auditory pathway underlying the computations of detection and localization is well understood. This analysis of the sensory information primarily determines the following orienting behavior towards the sound source. However, orienting behavior may be modulated by cognitive (top-down) influences such as attention. We show how advanced stimulation techniques can be used to determine the importance of different cues for sound localization in quasi-realistic stimulation situations, how attentional influences can improve the response to behaviorally relevant stimuli, and how attention can modulate related neural responses. Taken together, these data indicate how sound localization might function in the usually complex natural environment.

Journal Article↗
PubMed1999

Effect of positioning on recorded lung sound intensities in subjects without pulmonary dysfunction.

BACKGROUND AND PURPOSE: Physical therapists often use positioning to assist in the reexpansion of collapsed lung segments. An increase in lung sound intensity on auscultation is considered indicative of lung expansion. This study was designed to examine whether clinical interpretation of auscultatory findings is warranted. SUBJECTS: The subjects (5 male, 6 female) were young physical therapist students without pulmonary dysfunction (mean age=20.4 years, mean height=166.3 cm, mean weight=57.5 kg). Subjects with lung disease were excluded because pulmonary pathology is difficult to standardize. METHODS: Lung sounds electronically recorded over the posterior chest wall of subjects in sitting and side-lying positions were compared. Measures included peak intensity, frequency at maximum power, and median frequency. RESULTS: In the sitting position, inspiratory sounds recorded over the left posterior chest wall were louder than those recorded on the right side. In the side-lying positions, the sound intensity recorded from the dependent chest wall was louder than that recorded from the nondependent chest wall. In side-lying positions, the upper hemithorax is "nondependent," and the side in contact with the bed is "dependent." Sound intensities recorded over both posterior chest walls in the sitting position were louder than those recorded over the same lung area in the nondependent side-lying position. There was no difference in the sound intensity recorded between the sitting and dependent side-lying postures. CONCLUSION AND DISCUSSION: When comparative auscultation of the chest wall is used by physical therapists to assess the adequacy of pulmonary ventilation, patient posture and regional differences in breath sound intensity can influence clinical interpretation.

Adult↗
PubMed1995

Cerebral generators of mismatch negativity (MMN) and its magnetic counterpart (MMNm) elicited by sound changes.

Infrequent ("deviant") sounds occurring in a sequence of repetitive ("standard") sounds elicit an event-related brain potential (ERP) response called the mismatch negativity (MMN) even in the absence of attention to these sounds. MMN appears to be caused by a neuronal mismatch between the deviant auditory input and a sensory-memory trace representing the standard stimuli. This automatic mismatch process has presumably a central role in discrimination of changes in the acoustic environment outside the focus of attention. Thus, localizing cerebral generators of MMN might help identify brain mechanisms of auditory sensory memory and involuntary attention. This review summarizes results from studies aimed at localizing MMN generators on the basis of (1) scalp-distribution, (2) magnetoencephalographic (MEG), (3) intracranial, and (4) brain-lesion data. These studies indicate that a major MMN source is located in the auditory cortex. However, the exact location of this MMN generator appears to depend on which feature of a sound is changed (e.g., frequency, intensity, or duration), as well as on the complexity of the sound (e.g., a simple tone versus complex sound). Consequently, memory traces for different acoustic features, as well as for sounds of different complexity, might be located in different regions of auditory cortex. However, MMN appears to have generators in other brain structures, too. There is some evidence for contribution of frontal-lobe activity to the MMN, which might be related to the involuntary switching of attention to a stimulus change occurring outside the focus of attention. In addition, intracranial MMN recordings in animals suggest that at least in some species, MMN subcomponents also may be generated in the thalamus and hippocampus.

Acoustic Stimulation↗
PubMed2002

Effects of multi-channel compression time constants on subjectively perceived sound quality and speech intelligibility.

OBJECTIVE: The purpose of this study was to determine the influence of the compression time constants in a multi-channel compression hearing aid on both subjectively assessed speech intelligibility and sound quality in realistic binaural acoustical situations for normal-hearing and hearing-impaired listeners. DESIGN: A nonlinear hearing aid with 15 independent compression channels of approximated critical bandwidth was simulated on a personal computer. Various everyday life situations containing different sounds such as speech and speech in noise were recorded binaurally through original hearing aid microphones placed in BTE hearing aid cases. Two experiments were run with normal hearing and hearing-impaired subjects. For each subject, hearing thresholds were established using in situ audiometry. The static I/O-curve parameters in all channels of the hearing aid were then adjusted so that normal speech received an insertion gain corresponding to the NAL-R formula (Byrne & Dillon, 1986). The compression ratio was kept constant at 2.1:1. In the first experiment with six normal-hearing and six hearing-impaired subjects, the hearing aid was programmed to four different settings by changing only the compression time constants while all the parameters describing the static nonlinear Input/Output-curve were kept constant. The compression threshold was set to a very low value. In the second experiment with seven normal-hearing and eight hearing-impaired subjects, the hearing aid was programmed to four settings by changing the release time constants and the compression threshold while all other remaining parameters were kept constant. Using a complete A/B pair comparison procedure, subjects were presented binaurally with the amplified sounds and asked to subjectively assess their preference for each hearing aid setting with regards to speech intelligibility and sound quality. RESULTS AND CONCLUSIONS: In Experiment 1, all subjects showed a significant preference for the longest release time (4 sec) over the two shorter release times (400 msec and 40 msec), pertaining to quality and intelligibility. In combination with the long release time, the attack time (1 msec or 100 msec) was of less importance. Larger inter-individual differences were observed among all subjects with regard to the perceived sound quality of musical and nonspeech signals. In Experiment 2 the hearing-impaired subjects showed a significant preference for the hearing aid setting with a long release time (4 sec) and a low compression threshold (20 dB SPL), both with regard to sound quality and speech intelligibility. With a short release time (40 msec), a lower compression threshold (20 dB SPL) was preferred over a higher threshold (50 dB SPL). Among normal-hearing subjects, the same settings were also preferred for speech intelligibility. However, no significant differences were observed in these subjects regarding the assessment of sound quality. Again, more individual variability was found during the assessment of music and nonspeech signals. In sum, the preference of a rather long release time raises the question of whether a compression system with a very short time constant is the optimal means to compensate for the sensory recruitment phenomenon.

Acoustic Stimulation↗
PubMed2000

The adaptive significance of host location by vibrational sounding in parasitoid wasps.

Vibrational sounding, which is a form of echolocation, is a means of host location by some parasitoid wasps. The wasp taps the substrate (wood, stem or soil) and detects the position of a potential host through the returning 'echoes'. The deployment of vibrational sounding is inferred through the form of the subgenual organ in the female tibia in combination with the presence of modifications to the female antenna used for tapping the substrate. Vibrational sounding and its associated modifications were found in two families. The use of vibrational sounding by parasitoid wasps was positively correlated with the depth of the host in the substrate relative to the size of the parasitoid. There were also significant correlations between the use of vibrational sounding and parasitism of immobile and concealed hosts and between vibrational sounding and idiobiosis. The data suggested that vibrational sounding evolved under a variety of ecological conditions, being employed in the location of wood-boring, stem-boring, soil-dwelling and cocooned hosts and stem-nesting aculeates, often in situations in which the host does not produce vibrations itself.

Acoustics↗
PubMed1992

Auditory processing of complex sounds: an overview.

The past 30 years has seen a remarkable development in our understanding of how the auditory system--particularly the peripheral system--processes complex sounds. Perhaps the most significant has been our understanding of the mechanisms underlying auditory frequency selectivity and their importance for normal and impaired auditory processing. Physiologically vulnerable cochlear filtering can account for many aspects of our normal and impaired psychophysical frequency selectivity with important consequences for the perception of complex sounds. For normal hearing, remarkable mechanisms in the organ of Corti, involving enhancement of mechanical tuning (in mammals probably by feedback of electro-mechanically generated energy from the hair cells), produce exquisite tuning, reflected in the tuning properties of cochlear nerve fibres. Recent comparisons of physiological (cochlear nerve) and psychophysical frequency selectivity in the same species indicate that the ear's overall frequency selectivity can be accounted for by this cochlear filtering, at least in bandwidth terms. Because this cochlear filtering is physiologically vulnerable, it deteriorates in deleterious conditions of the cochlea--hypoxia, disease, drugs, noise overexposure, mechanical disturbance--and is reflected in impaired psychophysical frequency selectivity. This is a fundamental feature of sensorineural hearing loss of cochlear origin, and is of diagnostic value. This cochlear filtering, particularly as reflected in the temporal patterns of cochlear fibres to complex sounds, is remarkably robust over a wide range of stimulus levels. Furthermore, cochlear filtering properties are a prime determinant of the 'place' and 'time' coding of frequency at the cochlear nerve level, both of which appear to be involved in pitch perception. The problem of how the place and time coding of complex sounds is effected over the ear's remarkably wide dynamic range is briefly addressed. In the auditory brainstem, particularly the dorsal cochlear nucleus, are inhibitory mechanisms responsible for enhancing the spectral and temporal contrasts in complex sounds. These mechanisms are now being dissected neuropharmacologically. At the cortical level, mechanisms are evident that are capable of abstracting biologically relevant features of complex sounds. Fundamental studies of how the auditory system encodes and processes complex sounds are vital to promising recent applications in the diagnosis and rehabilitation of the hearing impaired.

Animals↗
PubMedDate not supplied

Infants' learning about words and sounds in relation to objects.

In acquiring language, babies learn not only that people can communicate about objects and events, but also that they typically use a particular kind of act as the communicative signal. The current studies asked whether 1-year-olds' learning of names during joint attention is guided by the expectation that names will be in the form of spoken words. In the first study, 13-month-olds were introduced to either a novel word or a novel sound-producing action (using a small noisemaker). Both the word and the sound were produced by a researcher as she showed the baby a new toy during a joint attention episode. The baby's memory for the link between the word or sound and the object was tested in a multiple choice procedure. Thirteen-month-olds learned both the word-object and sound-object correspondences, as evidenced by their choosing the target reliably in response to hearing the word or sound on test trials, but not on control trials when no word or sound was present. In the second study, 13-month-olds, but not 20-month-olds, learned a new sound-object correspondence. These results indicate that infants initially accept a broad range of signals in communicative contexts and narrow the range with development.

Child Development↗
PubMed2006

Sounding airflow enhances aerosol delivery into the paranasal sinuses.

BACKGROUND: The use of aerosol therapy is commonly suggested in the treatment of paranasal disorders but it is difficult to achieve an effective penetration of drugs into the sinuses. The authors have recently shown that an oscillating airflow produced by phonation (nasal humming) causes a large increase in the gas exchange between the nose and the paranasal sinuses. This is reflected by a high peak in nasally exhaled nitric oxide (NO) levels because NO accumulated in the sinuses is rapidly washed-out via the sinus ostia. OBJECTIVE: This study was designed to test whether the increase in sinus gas exchange caused by an oscillating airflow could be used to enhance penetration of a drug into the sinuses. MATERIALS AND METHODS: In six healthy subjects a nitric oxide-synthase inhibitor L-NAME was administrated into the nostrils by a jet nebulizer connected to a duck call, which could be modified to generate either a sounding airflow or a non-sounding airflow. The degree of L-NAME penetration into the sinuses was judged from the reduction in nasal NO during humming exhalations. Sinus drug deposition was also studied in a model of the nose and sinus. RESULTS: In humans the delivery of L-NAME with the non-sounding airflow had no effect on the NO levels achieved during humming, whereas L-NAME administration with sound caused a significant 22-35% reduction in nasal NO. In the model the aerosol delivery with the sounding airflow caused a fourfold increase in sinus drug deposition as compared with an aerosol without sound. CONCLUSION: A sounding airflow increases the delivery of an aerosolized drug into the paranasal sinuses.

Administration, Intranasal↗