Frequency Analysis Of Sounds Research Articles

Time–frequency analysis and classification of temporomandibular joint sounds

In this paper, we present a method for time–frequency analysis and classification of temporomandibular joint (TMJ) sounds based on evolutionary spectrum. Many researchers have worked on sounds recorded from patients with pain and/or mechanical disfunction at TMJ. It is generally accepted that a detailed analysis of TMJ sounds might offer valuable information for diagnosis and initiation of a treatment. In this work, TMJ sounds from patients with different symptoms were recorded by means of accelerometers during jaw opening and closing cycles. Then, four main categories of TMJ signals were defined based on patient's medical examination and evolutionary spectra. A method is presented to classify TMJ sounds using their joint time–frequency moments and neural networks.

Noise Control of a Table Fan

The cause of high noise generated by a table fan has been investigated. The noise source was identified by sound intensity mapping and frequency analysis of noise signal. The base of the fan stand was radiating high noise. The cause of this noise was found to be due to the resonance of fan stand. The excitation forcing frequencies were traced to the magnetic noise of the fan motor. A substantial noise reduction was achieved when the natural frequencies of fan stand were altered by stiffening its base and by increasing the mass of the base.

Neural analysis of sound frequency in insects

Summary Insects, like other hearing animals, must extract information from the sounds they hear so that they may respond appropriately. One parameter of sound that carries information is its frequency content. Insects analyze sound frequency to identify mates, to judge the distance to potential competitors, and to detect predators and prey. We review how frequency is analyzed in the insect nervous system, focusing on two taxa in which this problem has been studied most intensively, katydids and crickets. BioEssays 21:295‐303, 1999. r 1999 John Wiley & Sons, Inc.

Neural analysis of sound frequency in insects

Neural analysis of sound frequency in insects

Human complex sound analysis*

The analysis of complex sound features is important for the perception of environmental sounds, speech and music, and may be abnormal in disorders such as specific language impairment in children, and in common adult lesions including stroke and multiple sclerosis. This work addresses the problem of how the human auditory system detects features in complex sound, and uses those features to perceive the auditory world. The work has been carried out using two independent means of testing the same hypotheses; detailed psychophysical studies of neurological patients with central lesions, and functional imaging using positron emission tomography and functional magnetic resonance imaging of normal subjects. The psychophysical and imaging studies have both examined which brain areas are concerned with the analysis of auditory space, and which are concerned with the analysis of timing information in the auditory system. This differs from many previous human auditory studies, which have concentrated on the analysis of sound frequency. The combined lesion and functional imaging approach has demonstrated analysis of the spatial property of sound movement within the right parietal lobe. The timing work has confirmed that the primary auditory cortex is active as a function of the time structure of sound, and therefore not only concerned with frequency representation of sounds.

Human complex sound analysis*

The analysis of complex sound features is important for the perception of environmental sounds, speech and music, and may be abnormal in disorders such as specific language impairment in children, and in common adult lesions including stroke and multiple sclerosis. This work addresses the problem of how the human auditory system detects features in complex sound, and uses those features to perceive the auditory world. The work has been carried out using two independent means of testing the same hypotheses; detailed psychophysical studies of neurological patients with central lesions, and functional imaging using positron emission tomography and functional magnetic resonance imaging of normal subjects. The psychophysical and imaging studies have both examined which brain areas are concerned with the analysis of auditory space, and which are concerned with the analysis of timing information in the auditory system. This differs from many previous human auditory studies, which have concentrated on the analysis of sound frequency. The combined lesion and functional imaging approach has demonstrated analysis of the spatial property of sound movement within the right parietal lobe. The timing work has confirmed that the primary auditory cortex is active as a function of the time structure of sound, and therefore not only concerned with frequency representation of sounds.

Sound frequency analysis and the site of snoring in natural and sedation-induced sleep

Frequency analysis of snoring sounds has been shown to correlate with the site of upper airway narrowing. The aim of this study was to compare the sound frequency spectra of snores generated during induced snoring at sleep nasendoscopy with those during natural sleep. The sound of 11 subjects snoring overnight and during sleep nasendoscopy was digitally recorded. The observed site of vibration was noted for each snore sample recorded at sleep nasendoscopy. A Fast Fourrier Transformation was used to produce frequency spectra. At sleep nasendoscopy observed palatal snores (76) had a median peak frequency at 136 Hz, tongue based snores (10) at 1243 Hz and simultaneous palate and tongue (six) at 190 Hz. The median power ratios (defined as the area under the frequency spectra below 750 Hz/area above 750 Hz) were 33 for palatal snores, 0.2 for tongue base snores and 5 for simultaneous palate and tongue. Natural snores (275) had a dominant median peak at 132 Hz with a ratio of 88. A comparison of overnight snores (200) of those subjects (eight) with observed palatal snores (76) was made. Neither the peak frequency nor power ratio of natural and induced snores were significantly different (P = 0.85 and P = 0.13, respectively). The power ratio in four of the subjects individually was significantly different (P < 0.05). These results suggest that sedation-induced snores contain a high frequency component consistent with an element of tongue base snoring, not evident in natural snores. Thus sleep nasendoscopy may not accurately reflect snoring during natural sleep. Sound frequency analysis during natural sleep may therefore be a better predictive investigation for the success of palatal surgery.

Sound frequency analysis and the site of snoring in natural and sedation induced sleep

Frequency analysis of snoring sounds has been shown to correlate with the site of upper airway narrowing. The aim of this study was to compare the sound frequency spectra of snores generated during induced snoring at sleep nasendoscopy with those during natural sleep. The sound of 11 subjects snoring overnight and during sleep nasendoscopy was digitally recorded. The observed site of vibration was noted for each snore sample recorded at sleep nasendoscopy. A Fast Fourrier Transformation was used to produce frequency spectra. At sleep nasendoscopy observed palatal snores (76) had a median peak frequency at 136 Hz, tongue based snores (10) at 1243 Hz and simultaneous palate and tongue (six) at 190 Hz. The median power ratios (defined as the area under the frequency spectra below 750 Hz/area above 750 Hz) were 33 for palatal snores, 0.2 for tongue base snores and 5 for simultaneous palate and tongue. Natural snores (275) had a dominant median peak at 132 Hz with a ratio of 88. A comparison of overnight snores (200) of those subjects (eight) with observed palatal snores (76) was made. Neither the peak frequency nor power ratio of natural and induced snores were significantly different (P = 0.85 and P = 0.13, respectively). The power ratio in four of the subjects individually was significantly different (P < 0.05). These results suggest that sedation-induced snores contain a high frequency component consistent with an element of tongue base snoring, not evident in natural snores. Thus sleep nasendoscopy may not accurately reflect snoring during natural sleep. Sound frequency analysis during natural sleep may therefore be a better predictive investigation for the success of palatal surgery.

MRI acoustic noise: sound pressure and frequency analysis.

The large gradient coils used in MRI generate, simultaneously with the pulsed radiofrequency (RF) wave, acoustic noise of high intensity that has raised concern regarding hearing safety. The sound pressure levels (SPLs) and power spectra of MRI acoustic noise were measured at the position of the human head in the isocenter of five MRI systems and with 10 different pulse sequences used in clinical MR scanning. Each protocol, including magnetization-prepared rapid gradient echo (MP-RAGE; 113 dB SPL linear), fast gradient echo turbo (114 dB SPL linear), and spin echo T1/2 mm (117 dB SPL linear), was found to have the high SPLs, rapid pulse rates, amplitude-modulated pulse envelopes, and multipeaked spectra. Since thickness and SPL were inversely related, the T1-weighted images generated more intense acoustic noise than the proton-dense T2-weighted measures. The unfiltered linear peak values provided more accurate measurements of the SPL and spectral content of the MRI acoustic noise than the commonly used dB A-weighted scale, which filters out the predominant low frequency components. Fourier analysis revealed predominantly low frequency energy peaks ranging from .05 to approximately 1 kHz, with a steep high frequency cutoff for each pulse sequence. Ear protectors of known attenuation ratings are recommended for all patients during MRI testing.

Detection of tracheal stenosis by frequency analysis of tracheal sounds.

To develop a simple noninvasive method for detecting tracheal stenosis, tracheal sounds were analyzed using fast-Fourier transform. The subjects were all female and included 5 normal volunteers and 13 patients with tracheal stenosis mostly secondary to thyroid cancer (11 extrathoracic and 2 intrathoracic lesions). Tracheal sounds were recorded during spontaneous breathing and were digitized with an analog-to-digital converter. Pulmonary functions, including forced expiratory volume in 1 s (FEV1) expressed as percentage of vital capacity, peak expiratory flow rate (PEFR), the ratio of FEV1 to PEFR (Empey's index), and the ratio of expiratory to inspiratory flow rates at 50% vital capacity, were measured. A computed tomography scan was used to obtain the tracheal minimum cross-sectional area. Whereas PEFR demonstrated a weak correlation with the stenotic area, FEV1%, Empey's index, and the ratio of expiratory to inspiratory flow rates at 50% vital capacity did not. The power of the fast-Fourier transform spectrum of normal tracheal sounds decreased as the frequency increased up to 500 Hz. A small spectral peak was observed at approximately 1 kHz. Patients with significant tracheal stenosis demonstrated an increase in the peak spectral power at approximately 1 kHz and in the mean spectral power from 600 to 1,300 Hz in their tracheal sounds. In patients with extrathoracic lesions, the peak and mean spectral powers correlated well with the area of the stenosis as defined by computed tomography scan. In patients with intrathoracic lesions, abnormalities in the pulmonary functions as well as tracheal sound spectra appeared more evident despite milder stenoses.(ABSTRACT TRUNCATED AT 250 WORDS)

The frequency analysis of prosthetic valve sounds using digital transmission for remote diagnosis to detect the malfunction

The frequency analysis of prosthetic valve sounds using digital transmission for remote diagnosis to detect the malfunction

Noise surveys of hand-held pneumatic rock drills in Hong Kong

A study of the noise generated by hand-held pneumatic rock drills at 15 road works locations in Hong Kong was conducted in 1989. The locations of road construction works were identified over one week period. Sound pressure levels (SPL) and band frequency analysis were measured with the integrated sound level meter at the level of the operator's ears. The sound levels for all 15 operators exceeded the local statutory limit of 90 dBA. The average sound level was 107.4 dBA and the corresponding continuous equivalent level adjusted to 8 hours or L eq (8h) was 104.8 dBA. The sound levels for the octave frequencies from 125 Hertz to 8000 Hertz were all in excess of 90 dBA. Estimates of the risk of developing hearing impairment for conversation speech among the operators were 18% and 42% after 5 and 10 years of exposure, respectively. Although there is adequate statutory control to restrict and reduce the hazards caused by noise at road construction works to the workers and to the public at large, no noise control measures were noted at the work sites and none of the operators used hearing protection. This situation was compounded by the short-term nature of road works and the high mobility of the operators.

Study on Control of Oscillation Noise by Condensing Vapor in Water.

Measurements of sound pressure level and frequency analysis were carried out for the control of oscillation noise due to the condensation of vapor injected from submerged various orifices into subcooled water. The phenomena were observed by means of shadowgraphy using a still camera. Peak frequency and amount of the oscillaoion noise caused by the condensation of vapor were dependent on subcooling and shapes of injecting orifice. The effect of bulk temperature in a water tank and difference among a single-orifice, a multi-orifice, a prous-disc-orifice and the other orifice were discussed and good predictive results for the visualization in a quiescent subcooled water envirnoment.

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.

Spectral analysis of airflow sounds in patent versus occluded tracheostomy tubes: A pilot study in tracheostomized adult patients

Cannula occlusion is a life-threatening postoperative complication of tracheostomy. Current management largely relies on nursing care for prevention of fatalities because no proven mechanical, machine-based support monitoring exists. The objective of this paper was to address the problem of monitoring the state of cannula patency, based on analysis of airflow acoustic spectral patterns in tracheostomized adult patients in the patent and partially occluded cannula. Tracheal airflow sounds were picked up via a condenser microphone air-coupled to the skin just below the tracheal stoma. Signal output from Mic was amplified, high-pass filtered, digital tape-recorded, and analyzed on a mainframe computer. Although airflow frequencies for patient cannulae were predominantly low-pitched (0.1 to 0.3 kHz), occluded tubes had discrete high-pitched spectral peaks (1.3 to 1.6 kHz). These results suggest that frequency analysis of airflow sounds can identify a change in the status of cannula patency.

Frequency Analysis of Noxious Sounds Originated from Medical Instruments

Frequency Analysis of Noxious Sounds Originated from Medical Instruments

Ontogenetic change in the analysis of sound frequency in the infant rat.

Previous research has shown that there is an ontogenetic shift in the spatial code of sound frequency in the cochlea and central auditory nuclei. During ontogenesis, a given area of the basilar membrane or central auditory nuclei is maximally stimulated by sounds of progressively higher frequencies. Here, a similar ontogenetic shift in the rat's "perception" of sound frequency is reported. Animals were trained with a tone (CS) paired with footshock (US) and generalization of their conditioned response (CR) to different frequencies was assessed either 0.5 or 72 hr later. When 15-day-old animals were trained with an 8-kHz tone and tested 0.5 hr later, greater suppression of activity (CR) was evoked by the 8-kHz tone than by either a 12-kHz or a 6-kHz tone. When tested 72 hr after training, however, greater suppression of activity was evoked by a 12-kHz tone than by the 8-kHz training stimulus or by a 24-kHz tone. This shift in the peak of the generalization gradient could not be accounted for by changes in unconditioned responses to the test stimuli. Additionally, the observed shift in the generalization gradient was age-dependent. It was not observed when pups were trained at 18 days old and tested 72 hr later. The implications of these data for studies of the ontogenesis of learning and memory are discussed.

Accurate measurement of displacement by means of sound frequency in a resonant pipe. Theoretical analysis of sound frequency by blowing an air jet onto the open end of a pipe.

Sound generates when compressed air is blown onto the open-ended face of a small pipe. The sound frequency varies with the displacement of a solid placed close to another open-ended face of the pipe. This paper deals with the theoretical analysis of the sound frequency generated on the pipe. A theoretical investigation considers air jet behavior on the open-ended face, and the sound impedances both inside and outside of the pipe. The results of sample calculations for the theoretical frequency equation and the experiments coincide significantly for cases of large displacement ; however differences between both results are observed for cases of smaller displacement.

Frequency analysis of Ionescu-Shiley prosthetic closing sounds in patients with normally functioning prostheses.

To document the frequency distribution of lonescu-Shiley (IS) bovine pericardial xenograft valve sounds, a study was conducted on three groups of clinically stable subjects with valves implanted for less than 5 years. These groups consisted of 61 subjects with aortic IS valves, 28 subjects with mitral IS valves and 18 subjects with mitral Hancock porcine xenograft valves. Multiple comparisons with a Scheffe with mitral Hancock porcine xenograft valves. Multiple comparisons with a Scheffe test at level a=0.01 showed that the spectral characteristics of closing sounds produced by normal IS and Hancock xenografts implanted in the mitral position were both significantly different from those of IS xenografts implanted in the aortic position but not significantly different from each other. In addition, the spectral distribution of IS closing sounds was highly reproducible and very slightly affected by the duration of the implant up to 5 years.

Spectral analysis of heart sounds: Relationships between some physical characteristics and frequency spectra of first and second heart sounds in normals and hypertensives

Frequency analysis of heart sounds has been gaining recognition as a possible indicator of several heart and valve diseases, although a comprehensive study of normal heart sounds has not been published. Relating the frequency content of normal heart sounds to certain physical characteristics surrounding the generation of these sounds could lead to a valuable diagnostic tool and give a better understanding of the mechanism of heart sounds production. In this study, the first and second heart sounds from seventy-four normal, and seven hypertensive volunteers were recorded, digitized and analysed using a Fast Fourier Transform algorithm. Statistical analysis was used to relate physical characteristicss (sex, blood pressure, and body surface area) of the subjects to the frequency content of normal heart sounds and to compare normal and hypertensive heart sounds. Statistical analysis showed that the major concentration of energy, for both first heart sound (S1) and second heart sound (S2), is below 150 Hertz (Hz) which may indicate that both sounds are caused by vibrations within the same structure, possibly the entire heart. However S2 spectra have greater amplitude than S1 spectra above 150 Hz, which may be due to vibrations within the aorta and pulmonary artery. Relationships observed between body surface area, sex, blood pressure, and the frequency content of heart sounds indicate that as heart size increases, the amplitude of the frequency coefficients above 150 Hz decreases. These observations were more identifiable in the S1 spectra than in the S2 spectra, possibly because the S2 higher frequency components may mask subtle changes in the S2 spectra caused by heart size changes. However, when the changes in heart size are significant, as in hypertension or increased body surface area, trends in the S2 spectra can be observed.