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PubMedDate not supplied

A new approach to acoustical evaluation of human respiratory sounds.

The authors developed a method for more precise detection and analysis of the physical features of respiratory and voice sound transmission to the chest wall. Based on their findings using this method, they designed several devices for acoustic examination and evaluation of components of human respiratory sounds. These devices analyze forced expiratory sounds, distinguish between air-borne and structure-borne sounds, and distinguish abnormalities in voice transmission to the chest wall. Tests of the devices on human subjects confirmed the validity of the authors' theoretical models, which offer promise for the development of a new class of medical diagnostic instruments.

Acoustics↗
PubMed1998

Wheezing Lung Sounds Analysis with adaptive local trigonometric transform.

Wheezes are abnormal sounds which are known to be relevant to Chronic Obstructive Pulmonary Diseases (COPD). The analysis of such signals is especially useful in patient monitoring or pharmacology. Respiratory sounds are dependent on the flow and the volume. Furthermore, they can be the result of a complex mixture of events. The analysis of lung sounds can be greatly improved with time-frequency techniques because these methods highlight the evolution of the spectra of events. In this paper, we present the application of the Adaptive Local Trigonometric Decomposition (ALTD) to lung sound analysis. This analysis provides an optimal representation of the signal in the time-frequency domain with a lattice which is adapted in time. In our work, the parameterization of the ALTD is studied for the detection of wheezing phenomena.

Algorithms↗
PubMed1998

Sound- and/or pressure-induced vertigo due to bone dehiscence of the superior semicircular canal.

OBJECTIVES: To present symptoms, patterns of nystagmus, and computed tomographic scan identification of patients with sound- and/or pressure-induced vertigo due to dehiscence of bone overlying the superior semicircular canal. To describe anatomical findings and outcome in 2 patients undergoing plugging of the superior semicircular canal for treatment of these symptoms. DESIGN AND SETTING: Prospective study of a case series in a tertiary care referral center. PATIENTS AND RESULTS: Eight patients with vertigo, oscillopsia, and/or disequilibrium related to sound, changes in middle ear pressure, and/or changes in intracranial pressure were identified in a 2-year period. Seven of these patients also had vertical-torsional eye movements induced by these sound and/or pressure stimuli. The direction of the evoked eye movements could be explained by excitation or inhibition of the superior semicircular canal in the affected ear. Computed tomographic scans of the temporal bones identified dehiscence of bone overlying the affected superior semicircular canal in each case. Disabling disequilibrium in 2 patients prompted plugging of the dehiscent superior canal through a middle cranial fossa approach. Symptoms were improved in each case. One patient developed recurrent symptoms requiring an additional plugging procedure and developed sensorineural hearing loss several days after this second procedure. CONCLUSIONS: We have identified patients with a syndrome of vestibular symptoms induced by sound in an ear or by changes in middle ear or intracranial pressure. These patients can also experience chronic disequilibrium. Eye movements in the plane parallel to that of the superior semicircular canal were evoked by stimuli that have the potential to cause ampullofugal or ampullopetal deflection of this canal's cupula in the presence of a dehiscence of bone overlying the canal. The existence of such deshiscences was confirmed with computed tomographic scans of the temporal bones. Surgical plugging of the affected canal may be beneficial in patients with disabling symptoms.

Adult↗
PubMed1984

Mechanical vibration and sound levels experienced in neonatal transport.

Exposure of neonates to sound and to mechanical vibration was measured while transferring the neonates to a regional referral unit by ambulance and by rotary wing and fixed wing aircraft. Recordings were made during different phases of each type of transportation and were analyzed later. In the nursery, sound levels ranged from 72 to 74 dBA (A-weighted decibel level) (77 to 81 dB), while in transit, levels were higher at 78 to 99 dBA (90 to 110 dB), depending on the means of transport. Vibration was measured in the horizontal and vertical axes relative to the neonate in different frequency ranges. The vibration acceleration magnitude ranged from 0.4 m/sq s to 5.6 m/sq s, depending on the axis and type of transport; the maximum obtained was in rotary wing transport. When compared with adult tolerance levels, both sound and vibration exposure of the neonate are high and potentially hazardous. Further evaluation of vibration stress and means of attenuating sound and vibration in transport infant incubators is desirable to enhance the safety of transported infants.

Aircraft↗
PubMed1998

What sounds reach fetuses: biological and nonbiological modeling of the transmission of pure tones.

In utero transmission of external and maternal sounds has been studied in pregnant women and in an animal model of human species, the sheep. These works, especially the most recent ones, suggest that local and environmental factors interfere in such a way that signals are attenuated in a complex manner as frequency increases. The present work investigated whether a plain rubber sphere which was filled with water could be considered as a reliable nonbiological model in a study describing the characteristics of sound transmission. A sweeping pure tone, presented externally, was measured inside the rubber sphere using a high signal-to-noise ratio experimental hydrophone. A paradigmatic three components curve was observed between 100 and 20,000 Hz. In the first component of the curve (low to midfrequencies between 100 and 1,000 Hz), the intensity of the inside signal remained stable. The second component of the curve was composed of higher frequencies with the inside pressure falling gradually, demonstrating attenuation of the external signal. The third component of the curve appeared above a critical frequency, the value of which depended on several model and environment parameters. In this component, a series of rapid peaks and drops of the inside high frequency pressure was observed, indicating the presence of resonance systems. Analyses were carried out on the effects of several acoustical parameters, including: the size of the sphere, the location of the hydrophone in the sphere, the distance between the signal source and the hydrophone, the location of the external reference microphone, and the acoustical structure of the environment. These parameters allowed for the definition of their respective roles in the in-utero transmission of external sounds. These data were then compared with measurements performed within a biological model--ewes--under close acoustical settings. The comparisons confirmed the validity of the measurements, suggesting that the model may be useful in studies of sound transmission in utero.

Acoustic Stimulation↗
PubMed1990

Frequency analysis of the first heart sound for patients on chronic hemodialysis.

According to Adolph et al., valuable information on the nature of myocardium can be obtained through frequency analysis of first heart sounds (S1) during the isometric contraction phase (ICP). We compared dominant frequencies (DF), which were defined as the frequency of maximum sound voltage, of S1 among 37 outpatients undergoing chronic hemodialysis (HD group) and 28 outpatients with neurosis (control group). Heart sounds, which were obtained at apex by a sound microphone and polygraph, were analyzed into frequency spectra by the maximum entropy method through a computer. Left ventricular dimensions and wall thickness were measured by echocardiography. Histories of hemodialysis ranged from 4 to 164 months, with an average of 54 months. Age and body weight of patients before each hemodialysis were comparable with control subjects. Although systolic blood pressure, left ventricular mass (LVM), and combined left ventricular mass (CLVM), which means LVM and the blood it contains, showed higher values in the HD group, the ratio of LVM and CLVM and ejection fraction were almost equal in both groups. Therefore, if elastic tissue of myocardium of HD patients is less, lower DF is expected. However, DFs were 22.6 +/- 7.8 Hz in the HD group and 22.6 +/- 9.6 Hz in the control group. It was concluded that (1) hypertension and overhydration were not primary causes of uremic cardiomyopathy, and (2) myocardium of HD patients received no significant damage if cardiac function remained intact, even through left ventricular hypertrophy and dilatation were induced.

Adult↗
PubMed1992

Visual factors in sound localization in mammals.

The ability of mammals to localize sound varies widely among species. During the past decade, evidence has accumulated that this variation cannot be accounted for simply on the basis of the availability of the physical cues for locus. Evidence is presented that a major factor in sound localization is the need to direct the field of best vision to a sound source for further scrutiny. Thus, species with broad fields of best vision (such as visual streaks) require less accurate information regarding the location of a sound source than do species with very narrow fields of best vision (such as foveae). To support this suggestion, data are reported for the width of the field of best vision in the form of retinal ganglion cell isodensity contours for thirteen species of mammals. The possible contribution of other factors including binocular fields, visual acuity, and the degree to which a species is predatory in lifestyle, is also examined.

Animals↗
PubMed1986

Development of auditory localization in dogs: single source and precedence effect sounds.

The development of auditory localization in dogs was investigated in a litter of 12 pups. Behavioral auditory localization consisted of orienting responses to dog vocalizations presented from loudspeakers 90 degrees to each side. Sounds were presented in two configurations, single source (only one loudspeaker) and precedence effect (both loudspeakers, with one slightly leading the other). Localization began around 16 days after birth, for single-source sounds. This is consistent with previous observations and with findings on dogs' auditory neural development. Single-source sounds were localized earlier during development than precedence-effect sounds. This ordering resembles findings on human infants and can be related to neuroanatomical investigations of mammalian brain structures mediating single source versus precedence effect localization.

Age Factors↗
PubMed2004

Different areas of human non-primary auditory cortex are activated by sounds with spatial and nonspatial properties.

In humans, neuroimaging studies have identified the planum temporale to be particularly responsive to both spatial and nonspatial attributes of sound. However, a functional segregation of the planum temporale along these acoustic dimensions has not been firmly established. We evaluated this scheme in a factorial design using modulated sounds that generated a percept of motion (spatial) or frequency modulation (nonspatial). In addition, these sounds were presented in the context of a motion detection and a frequency-modulation detection task to investigate the cortical effects of directing attention to different perceptual attributes of the sound. Motion produced stronger activation in the medial part of the planum temporale and frequency-modulation produced stronger activation in the lateral part of the planum temporale, as well as an additional non-primary area lateral to Heschl's gyrus. These separate subregions are consistent with the notion of divergent processing streams for spatial and nonspatial auditory information. Activation in the superior parietal cortex, putatively involved in the spatial pathway, was dependent on the task of motion detection and not simply on the presence of acoustic cues for motion. This finding suggests that the listening task is an important determinant of how the processing stream is engaged.

Acoustic Stimulation↗
PubMed1999

Classification of asthmatic breath sounds: preliminary results of the classifying capacity of human examiners versus artificial neural networks.

For continuous monitoring of the respiratory condition of patients, e.g., at the intensive care unit, computer assistance is required. Existing mechanical devices, such as the peak expiratory flow meter, provide only with incidental measurements. Moreover, such methods require cooperation of the patient, which at, e.g., the ICU is usually not possible. The evaluation of complicated phenomena such as asthmatic respiratory sounds may be accomplished by use of artificial neural networks. To investigate the merit of artificial neural networks, the capacities of neural networks and human examiners to classify breath sounds were compared in this study. Breath sounds were in vivo recorded from 50 school-age children with asthma and from 10 controls. Sound intervals with a duration of 20 seconds were randomly sampled from asthmatics during exacerbation, asthmatics in remission, and controls. The samples were digitized and related to peak expiratory flow. From each interval, two full breath cycles were selected. Of each selected breath cycle, a Fourier power spectrum was calculated. The so-obtained set of spectral vectors was classified by means of artificial neural networks. Humans evaluated graphic displays of the spectra. Human examiners could not clearly discriminate between the three groups by inspecting the spectrograms. Classification by self-classifying neural networks confirmed the existence of at least three classes; however, discrimination of 11 classes seemed more appropriate. Good results were obtained with supervised networks: as much as 95% of the training vectors could be classified correctly, and 43% of the test vectors. The three patient groups, as discriminated in advance, do not correspond with three sharply separated sets of spectrograms. More than three classes seem to be present. Humans cannot take up the spectral complexity and showed negative classification results. Artificial neural networks, however, are able to handle classification tasks and show positive results.

Acoustics↗
PubMed2002

Sustained magnetic fields reveal separate sites for sound level and temporal regularity in human auditory cortex.

Magnetoencephalography was used to investigate the relationship between the sustained magnetic field in auditory cortex and the perception of periodic sounds. The response to regular and irregular click trains was measured at three sound intensities. Two separate sources were isolated adjacent to primary auditory cortex: One, located in lateral Heschl's gyrus, was particularly sensitive to regularity and largely insensitive to sound level. The second, located just posterior to the first in planum temporale, was particularly sensitive to sound level and largely insensitive to regularity. This double dissociation to the same stimuli indicates that the two sources represent separate mechanisms; the first would appear to be involved with pitch perception and the second with loudness. The delay of the offset of the sustained field was found to increase with interclick interval up to 200 ms at least, which suggests that the sustained field offset represents a sophisticated offset-monitoring mechanism rather than simply the cessation of stimulation.

Acoustic Stimulation↗
PubMed1985

Sound graphs: a numerical data analysis method for the blind.

A system for the creation of computer-generated sound patterns of two-dimensional line graphs is described. The objectives of the system are to provide the blind with a means of understanding line graphs in the holistic manner used by those with sight. A continuously varying pitch is used to represent motion in the x direction. To test the feasibility of using sound to represent graphs, a prototype system was developed and human factors experimenters were performed. Fourteen subjects were used to compare the tactile-graph methods normally used by the blind to these new sound graphs. It was discovered that mathematical concepts such as symmetry, monotonicity, and the slopes of lines could be determined quickly using sound. Even better performance may be expected with additional training. The flexibility, speed, cost-effectiveness, and greater measure of independence provided the blind or sight-impaired using these methods was demonstrated.

Adult↗
PubMed1990

Clinical application of spectral analysis of bowel sounds in intestinal obstruction.

The bowel sounds of 21 patients with mechanical obstruction of the intestine were studied. A computer analysis of bowel sounds was performed using a signal processor. Bowel sounds of patients were classified into 3 types (Types I, II, and III) based on the histograms, although these were not distinguishable on auscultation. The lower, peak, and upper frequencies were 173 +/- 25 Hz, 273 +/- 64 Hz, and 667 +/- 58 Hz, respectively, in Type I; 309 +/- 121 Hz, 632 +/- 94 Hz, and 878 +/- 116 Hz, respectively, in Type II; and 330 +/- 120 Hz, 612 +/- 86 Hz, and 766 +/- 82 Hz, respectively, in Type III. High frequency sounds above 900 Hz were recorded in Types I and II but not in Type III. The ratio of the operated patients was 0, 23, and 100 percent in Types I, II, and III, respectively. The intervals between the times of admission and operation were 4.3 days and 1.2 days in Types II and III, respectively. Thus, it appears that the methods described by the authors could provide a very objective assessment of the severity and help determine the treatment (conservative or operative) of each patient.

Adult↗
PubMed1989

Muscular sound and force relationship during isometric contraction in man.

The contracting muscle generates a low frequency sound detectable at the belly surface, ranging from 11 to 40 Hz. To study the relationship between the muscular sound and the intensity of the contraction a sound myogram (SMG) was recorded by a contact sensor from the biceps brachii of seven young healthy males performing 4-s isometric contractions from 10% to 100% of the maximal voluntary contraction (MVC), in 10% steps. Simultaneously, the electromyogram (EMG) was recorded as an index of muscle activity. SMG and EMG were integrated by conventional methods (iSMG and iEMG). The relationship between iSMG and iEMG vs MVC% is described by parabolic functions up to 80% and 100% MVC respectively. Beyond 80% MVC the iSMG decreases, being about half of its maximal value at 100% MVC. Our results indicate that the motor unit recruitment and firing rate affect the iSMG and iEMG in the same way up to 80% MVC. From 80% to 100% MVC the high motor units' discharge rate and the muscular stiffness together limit the pressure waves generated by the dimensional changes of the active fibres. The muscular sound seems to reflect the intramuscular visco-elastic characteristics and the motor unit activation pattern of a contracting muscle.

Adult↗
PubMed2003

Discrimination analysis of discontinuous breath sounds using higher-order crossings.

The paper evaluates the performance of an automatic discrimination analysis (DA) method used to discriminate efficiently the types of discontinuous breath sound (DBS), i.e. fine crackles (FCs), coarse crackles (CCs) and squawks (SQs); this may lead to more accurate characterisation of the pulmonary acoustical changes due to the related pathology. Based on higher-order crossings (HOCs), the proposed method, HOC-DA, captured the differences in the oscillatory patterns of FCs, CCs and SQs, which are only exposed when higher (> 1) crossings are employed. Prior to HOC-DA, wavelet-based de-noising of DBSs was employed to eliminate the effects of the vesicular sound (background noise) from their oscillatory pattern. The HOC-DA was applied to 157 discontinuous breath sounds corresponding to 16 cases included in three lung sound databases. Results showed that the HOC-DA efficiently separated FCs from CCs, SQs from CCs (both with an accuracy of 100%), and SQs from FCs (accuracy of 80%), with the optimum order ranging from 9 to 11. When compared with other classification tools, the HOC-DA resulted in high discrimination accuracy without involving high computational complexity. Owing to its simplicity, it could be implemented in a real-time context and be used in clinical medicine as a module of an integrated intelligent patient evaluation system.

Auscultation↗
PubMed2002

Estimation of pulmonary arterial pressure by a neural network analysis using features based on time-frequency representations of the second heart sound.

The objective of the study was to develop a non-invasive method for the estimation of pulmonary arterial pressure (PAP) using a neural network (NN) and features extracted from the second heart sound (S2). To obtain the information required to train and test the NN, an animal model of pulmonary hypertension (PHT) was developed, and nine pigs were investigated. During the experiments, the electrocardiogram, phonocardiogram and PAP were recorded. Subsequently, between 15 and 50 S2 heart sounds were isolated for each PAP stage and for each animal studied. A Coiflet wavelet decomposition and a pseudo smoothed Wigner-Ville distribution were used to extract features from the S2 sounds and train a one-hidden-layer NN using two-thirds of the data. The NN performance was tested on the remaining one-third of the data. NN estimates of the systolic and mean PAPs were obtained for each S2 and then ensemble averaged over the 15-50 S2 sounds selected for each PAP stage. The standard errors between the mean and systolic PAPs estimated by the NN and those measured with a catheter were 6.0 mmHg and 8.4 mmHg, respectively, and the correlation coefficients were 0.89 and 0.86, respectively. The classification accuracy, using 23 mmHg mean PAP and 30 mmHg systolic PAP thresholds between normal PAP and PHT, was 97% and 91%, respectively.

Animals↗
PubMedDate not supplied

Dynamical analysis of diastolic heart sounds associated with coronary artery disease.

In a new approach to noninvasively diagnose coronary artery disease (CAD), auditory correlates attributed to blood flow turbulence have been associated with stenosed coronary arteries. These auditory components have been detected in diseased subjects by spectral estimation of diastolic heart sound recordings made on the surface of the chest. In this study, we investigated the dynamics of the process that produces these sounds in diseased subjects by applying the techniques of dimensional analysis. Our results indicate a difference in the "correlation dimension" between heart sounds of diseased and normal subjects. In particular, diseased subjects show a fractal dimension, implying the presence of a strange attractor and the possible existence of low-dimensional chaos in sounds associated with coronary artery disease.

Algorithms↗
PubMed1994

Quantification of first heart sound frequency dynamics across the human chest wall.

Power spectral analysis has attracted attention because of its potential for non-invasive cardiac diagnosis. However, time-frequency analysis of first heart sound frequency dynamics from canine epicardium has demonstrated that cardiac vibrations are fundamentally multi-component and non-stationary, questioning the validity of power spectral techniques. In this study, we employed time-frequency transforms to characterise first heart sound frequency dynamics from 27 sites across the human thorax. In contrast to the dynamics observed epicardially, the first heart sound frequency law was dominated by quasi-stationary and impulse-like components implying that the instantaneous power and the power spectrum contain most of the diagnostic information in the first heart sound.

Adult↗