Sound Spectrum Analysis Research Articles

Intraction between tracheal sound and flow rate: a comparison of some different flow evaluations from lung sounds

We simultaneously recorded tracheal sound and air flow from nine normal subjects (seven males and two females). Sound was picked up at the supra sternal notch with an air-coupled sensitive microphone held in a small airtight probe. Flow was measured at the mouth using a pneumotachograph Fleisch n degrees 2. Both sound and flow were directly digitized at a sampling rate of 5120 Hz and then divided in 128-sample blocks. For each sound block the frequency spectrum was computed using the fast Fourier transform. In order to evaluate instantaneous flow-rate from tracheal sounds we investigated eight methods divided in two groups of four. In the first group (i.e., reference curves methods), we assumed that a relationship existed between sound and flow and was thus reflected by the variations of certain parameters. We chose to use simple straightforward relationships, already known and published. We tested four different parameters. During a calibration phase, we built for each parameter P a reference curve representing the variations of P versus flow and being specific to each subject. Then, an unknown flow was evaluated in calculating P on a 128-sample block, and the reference curve gave the corresponding flow. In the second group, we made a hierarchial clustering analysis of sound spectra for revealing the frequency modifications, induced by the flow. We tested two kinds of spectra as well as two ways of associating a flow to a given cluster. This led us to four other methods for calculating the flow. All the eight methods but one gave a mean uncertainty in the measure of flow of about 15%.(ABSTRACT TRUNCATED AT 250 WORDS)

Source correlation effects on the sound power radiation from spherical shells

The sound power radiated from a fluid-loaded thin spherical shell under the action of correlated axisymmetric annular forces is formulated in this study. By assuming that two forces possess identical bandlimited white-noise spectra, uniformly distributed against the equator of the spherical shell, numerical evaluations of the nondimensional sound power are performed for a steel shell immersed in air and water, respectively. The results show that (1) keeping the input power the same, point forces always produce higher sound power levels than distributed forces; (2) when the band of excitation falls into a relatively low frequency region where only very few, if any, shell modes can be excited, the cross spectra between forces generally have important effects on the radiated sound power level; (3) when the band covers a relatively wide frequency range where more shell modes can be excited, the role of source correlations becomes important only if the two forces are located close to one another; (4) when two forces are positively correlated (r=+1), there always exists an optimal separation distance (expressed as angle Θ1) between the two forces that will produce a relatively minimum sound power level. This phenomenon of sound power reduction is discussed by means of sound power spectrum analysis. These conclusions are applicable for spherical shells immersed in air and in water.

Light Scattering Analysis of Strained-Layer Superlattices

ABSTRACTRaman scattering has been used to examine strained-layer GaSb/AlSb superlattices for a variety of growth imperfections. Analysis of zone-folded acoustic phonon spectra permit a determination of the superlattice period, the individual layer widths, some estimate of the interfacial widths, and evidence for variations in layer thicknesses.

Effect of quantitated stenoses on arterial sound spectrum analysis

Spectral analysis of carotid Doppler signals has been shown to be accurate in determining the degree of carotid artery stenosis when compared with arteriography. Since the Doppler angle and the amount of gain used during measurement may affect results, an in vitro study was performed measuring peak frequency, mode frequency, and percent window at various Doppler angles and gains to determine if these latter factors could affect results of the test. A spectrum analyzer with an 8 MHz continuouswave Doppler probe was utilized. Seven cross-sectional area stenoses (0 to 100 percent) were applied to an undiseased bifurcated cadaver artery which was suspended in a saline bath and placed in a pulsatile circulatory system. At each stenosis, peak frequency, mode frequency, and percent window were measured at three Doppler angles (45 degrees, 60 degrees, and 75 degrees) at a constant gain and at three different gains (low, medium, and high) at a constant Doppler angle of 60 degrees. Arterial pressure was measured distal to the stenoses. Critical stenoses were present at greater than 82 percent area reduction. At a Doppler angle of 60 degrees and medium gain, correlation coefficients between percentage of stenosis and peak frequency, mode frequency, and percent window were 0.9520, 0.8369, and −0.9861, respectively. However, peak frequency and mode frequency actually decreased at stenotic areas of more than 82 percent and were similar to frequencies seen at stenotic areas of 61 percent. Peak frequency significantly decreased as Doppler angle increased, so there was an even greater overlap of peak frequency values at larger angles. Percent window did not appear to be affected by Doppler angle. At an angle of 60 degrees and different gains, there appeared to be very little overlap of percent window values between any stenoses. Peak frequency and mode frequency did not appear to be affected by gain. This study demonstrates an excellent correlation between percentage of stenosis and peak frequency and percent window. However, peak frequency was significantly affected by changes in Doppler angle and did not differentiate subcritical (61 percent) from critical (96 percent) stenoses. Percent window, however, was not significantly affected by Doppler angle or gain and was able to differentiate between all degrees of stenosis.

Auditory profile analysis of irregular sound spectra.

The discrimination of changes in the shapes of sound spectra is reported. The change was always an intensity increment to the 948-Hz component of a multitone complex. First, the ability of naive listeners to learn to discriminate a change in a "regular" background or reference spectrum (equal-level tones equally spaced in logarithmic frequency) was measured as a function of the number of trials. On the average, threshold improved about 10 dB over 3000 trials, with about 50% of the decrease in threshold occurring during the first 750 trials. In a subsequent series of experiments, the overall pattern of spectral shape of the background was varied randomly. Two kinds of perturbations in spectral shape were employed: Randomly choosing the frequencies of the reference spectra and randomly choosing the amplitudes of the components of the reference spectra. The experimental manipulations involved fixing the random spectra across a block of trials, varying the reference spectra from interval to interval of each trial, and providing extensive practice in discriminating specific randomly perturbed reference spectra. The results of the spectrum-learning and random perturbation experiments provide insight into the roles of critical band filtering, sensory variability, and short-term and long-term memory representations in auditory profile analysis. Further, the appropriateness of the generalization of a simple energy detection model is discussed.

Relative accuracy of the diagnostic components of noninvasive carotid arterial tests: A comparison of pulsed Doppler arteriography and spectrum analysis

Pulsed Doppler ultrasonography (UA), sound spectrum analysis, and subjective interpretation of the audible signal are valuable methods for assessing carotid arterial disease; however, the relative contribution of each in making a diagnosis is disputed. To investigate this issue, 258 noninvasive carotid studies with measured x-ray comparisons were reviewed. Internal carotid spectra, UA images, and images combined with the technician's comments were each interpreted blindly by three independent readers. Percentage of stenosis was categorized into six groups: 0, 1% to 24%, 25% to 49%, 50% to 74%, 75% to 99%, and 100%. Each reader's assessment of the individual noninvasive components and his overall reading of the complete study were compared with x-ray findings and with those of the other two readers. The readings of the three observers were consistent within each diagnostic component (p < 0.001). For each reader, the technician's comments significantly improved the accuracy of ultrasonic imaging alone (p < 0.001). Spectrum analysis was as good as the image plus technician's comments and, for two of three readers, was better than the image alone (p < 0.001).

Hemodynamic study by doppler sound spectrum analysis of aortic valvular disease

Hemodynamic study by doppler sound spectrum analysis of aortic valvular disease

Precise comparison of experimental and theoretical SNRs in CO_2 laser heterodyne systems

A detailed comparison of experimental and theoretical SNR in an IR laser heterodyne system has been made with three different signal analyzers. Good agreement, considerably better than a factor of 1.5, is reported. Accurate allowance was made for transmission in the receiver optics, the effective quantum efficiency of the detector due to shot noise domination by the local oscillator, and for coherent speckle effects across the collection aperture. The evaluation of SNR with a surface acoustic wave spectrum analyzer and digital integrator is described in some detail. As an illustration an absolute measurement of backscattering strength in the atmosphere from an airborne equipment at altitudes up to 13.1 km is provided.

Evaluation of transplant renal artery blood flow by Doppler sound-spectrum analysis.

Doppler ultrasonography sound-spectrum analysis (SSA) was used to evaluate blood flow in the transplanted kidney and its renal artery. Seven patients with posttransplant hypertension and a bruit over the transplanted kidney were screened for renal artery stenosis (RAS). In five patients, RAS was diagnosed by SSA, and in two it was not. These findings were confirmed by subsequent angiography in all patients. Three patients studied after surgical correction of their RAS had improvement in their SSA patterns. Fourteen hypertensive patients with a cause other than RAS were evaluated by SSA. None of them had SSA findings suggestive of RAS. Doppler ultrasonography with SSA is an effective, noninvasive technique of monitoring transplant renal blood flow, especially in the screening of hypertensive transplant recipients for transplant RAS.

EFFICACY OF SALBUTAMOL IN TREATMENT OF INFANT PERTUSSIS DEMONSTRATED BY SOUND SPECTRUM ANALYSIS

The value of sound spectrum analysis (sonography) as an indicator of the severity of symptomatic pertussis was assessed in four infants aged 3 weeks to 5 months. Coughing paroxysms and whooping could be clearly distinguished and measured on the sonogram. Sonography was then used to evaluate the effects of oral salbutamol on pertussis. The drug reduced the frequency and shortened the duration of the whoops; however, it did not have corresponding effect on the cough. Salbutamol seemed to relieve the laryngeal spasms and consequently eased the infant's breathing difficulties.

On the multivariate analysis of avian vocalizations

In a recent paper in this journal, Sparling & Williams (1978) demonstrated several multivariate techniques by applying them to measurements of albatross calls. Their paper contains a useful summary of the literature, but includes several misleading interpretations of the analyses. Since the stated purpose of that article was to familiarize biologists with proper uses of the statistical methods, it is important to clarify the problems, some of which I discuss below. I then mention how such techniques are likely to be particularly valuable in the near future, when coupled with real-time sound spectrum analysis.

Speaker Sex Identification Utilizing a Constant Laryngeal Source

It has been demonstrated that the sex of speakers can be reliably and accurately identified in the absence of idiosyncratic glottal wave forms. This finding led to the hypothesis that there are other sex‐related differences in the supraglottal vocal tract which produce discriminable acoustic differences in speech. As a test of this hypothesis, ten males and ten females counted to ten and read the second sentence of the “Rainbow Passage” using an electronic artificial larynx (F0=120 Hz) with a closed glottis. Tho vocalizations were tape recorded, randomized, and played to 30 listeners who then determined the speakers' sex. Later, the vocalizations were subjected to a sound spectrum analysis. Results indicated that male voices with energy concentrations shifted toward the lower frequencies were identified above chance as were females with energy concenctrations shifted toward the higher frequencies. Speakers whose energy concentrations were centralized were most often confused. These results confirm the hyp...

Speaker sex identification utilizing a constant laryngeal source

It has been demonstrated that the sex of speakers can be reliably and accurately identified in the absence of idiosyncratic glottal wave forms. This finding led to the hypothesis that there are other sex-related differences in the supraglottal vocal tract which produce discriminable acoustic differences in speech. As a test of this hypothesis, ten males and ten females counted to ten and read the second sentence of the “Rainbow Passage” using an electronic artificial larynx (F0=120 Hz) with a closed glottis. Tho vocalizations were tape recorded, randomized, and played to 30 listeners who then determined the speakers' sex. Later, the vocalizations were subjected to a sound spectrum analysis. Results indicated that male voices with energy concentrations shifted toward the lower frequencies were identified above chance as were females with energy concenctrations shifted toward the higher frequencies. Speakers whose energy concentrations were centralized were most often confused. These results confirm the hypothesis that sex-related supraglottal vocal tract characteristics play a major role in the identification of speaker sex.

FREQUENCY MODULATION INCONOCEPHALUS NIGROPLEURUM, THE BLACK-SIDED MEADOW KATYDID (ORTHOPTERA: TETTIGONIIDAE)

AbstractFrequency modulation has been discovered in the calling song of a conocephaline katydid,Conocephalus nigropleurum(Bruner). Real time sound spectrum analysis reveals a drop of 5 khz during the closing wingstroke.

New Evidence on the Persisting Nuclei

The laboratory evaluation of the acoustic microbubble spectrum analyzer has disclosed several types of persisting microbubble phenomena as a varying abnormal attenuation with frequency. Microbubble populations are detected in a tank filled with tap water only sporadically and may be influenced significantly by barometric pressure. Distilled water open to the atmosphere can become rapidly charged with persisting microbubbles. An increase of temperature or a reduction of local pressure can be used to expand microbubbles into the detection range of the instrument. For limited excursions of temperature and pressure, the change in attenuation is reversible, indicating a stability range for persisting microbubbles. The observed attenuation spectra include examples of sharp peaks, which indicate a narrow range of microbubble size, and broad peaks, which indicate a distribution of sizes. [This work supported in part by the Office of Naval Research.]

Use of thermosensitive paper in sound-spectrum analysis.

The use of thermosensitive paper is mooted in the design of an all-purpose sound-spectrum analyzer that would instantaneously and continuously provide both display and permanent graphic record. Some applications and extensions of the technique are suggested.

Refracting Sound Waves

Structures are described which refract and focus sound waves. They are similar in principle to certain recently developed electromagnetic wave lenses in that they consist of arrays of obstacles which are small compared to the wave-length. These obstacles increase the effective density of the medium and thus effect a reduced propagation velocity of sound waves passing through the array. This reduced velocity is synonymous with refractive power so that lenses and prisms can be designed. When the obstacles approach a half wave-length in size, the refractive index varies with wave-length and prisms then cause a dispersion of the waves (sound spectrum analyzer). Path length delay type lenses for focusing sound waves are also described. A diverging lens is discussed which produces a more uniform angular distribution of high frequencies from a loud speaker.

A New Analyzer for the Audible Frequency Range

This instrument was designed for comparatively rapid analysis of sound spectra produced by musical instruments. It is a heterodyne analyzer using an intermediate frequency of 20 kilocycles per second. The filter is a magnetostrictive resonator of very low decrement capable of distinguishing between two frequency components only forty cycles per second apart while differing by some fifty decibels in amplitude. The amplitudes are measured by a logarithmic voltmeter controlling a cathode-ray oscillograph which records their relative magnitude, calibrated directly in decibels, on a strip of photographic paper. The recording camera is geared to the oscillator which furnishes the heterodyne frequency in such a way that the audible range up to 10,000 cycles per second may be swept out in a comparatively short time. Every effort has been made to reduce the duration of transients in the system. Preliminary tests indicate that a complete analysis may be made in about twenty seconds.