Individual Frequency Bands Research Articles

A Study of the Influence of Muscle Type and Muscle Force Level on Individual Frequency Bands of the EMG Power Spectrum

The aim of this study was to analyse the electromyographic (EMG) power spectrum indicating differences in the frequency bands of the spectrum resulting from differences in muscle type and force level for the extensor digitorum (ED), palmaris longus (PL) and biceps brachii (BB) muscles. The study was performed on 12 young men as 2 tests different in terms of the type of exerted force (30, 15 and 5% MVC, maximum voluntary contraction). The parameters of the EMG power spectrum were obtained as a result of a division of the EMG power spectrum into ranges determined by border frequencies. The results suggest that (a) frequency bands contained in the 30-80 Hz range and over the frequency of 300 Hz depend on muscle force, and (b) the power spectrum in the frequency range of up to 40 Hz and 60-300 Hz indicates muscle type.

Determination of the Potential Benefit of Time-Frequency Gain Manipulation

The purpose of this study was to determine the maximum benefit provided by a time-frequency gain-manipulation algorithm for noise-reduction (NR) based on an ideal detector of speech energy. The amount of detected energy necessary to show benefit using this type of NR algorithm was examined, as well as the necessary speed and frequency resolution of the gain manipulation. NR was performed using time-frequency gain manipulation, wherein the gains of individual frequency bands depended on the absence or presence of speech energy within each band. Three different experiments were performed: (1) NR using ideal detectors, (2) NR with nonideal detectors, and (3) NR with ideal detectors and different processing speeds and frequency resolutions. All experiments were performed using the Hearing-in-Noise test (HINT). A total of 6 listeners with normal hearing and 14 listeners with hearing loss were tested. HINT thresholds improved for all listeners with NR based on the ideal detectors used in Experiment I. The nonideal detectors of Experiment II required detection of at least 90% of the speech energy before an improvement was seen in HINT thresholds. The results of Experiment III demonstrated that relatively high temporal resolution (<100 msec) was required by the NR algorithm to improve HINT thresholds. The results indicated that a single-microphone NR system based on time-frequency gain manipulation improved the HINT thresholds of listeners. However, to obtain benefit in speech intelligibility, the detectors used in such a strategy were required to detect an unrealistically high percentage of the speech energy and to perform the gain manipulations on a fast temporal basis.

Changes in Respiratory Rate, Blood Pressure and Heart Rate Variability in Rabbits during Orthostasis

The purpose of the study was to evaluate the changes of respiratory rate, systemic blood pressure and heart rate variability parameters (HRV) during orthostasis in anaesthetized rabbits. Furthermore, these changes were influenced by affecting the renin-angiotensin-aldosterone (RAA) system and autonomic nervous system (ANS) to study the mechanisms participating in activity of spectral frequency bands of HRV in rabbits. Ten adult rabbits (Chinchilla) were anaesthetized by ketamine and flunitrazepam. The systemic blood pressure, tidal volume and respiratory rate were measured. HRV was evaluated by microcomputer system VariaPulse TF3E. The R-R intervals were derived from the electrocardiogram signal from subcutaneous needle electrodes. The evaluation of HRV in very low (VLF; 0.01-0.05 Hz), low (LF; 0.05-0.15 Hz) and high frequency bands (HF; 0.15-2.0 Hz) was made and parameters of frequency and time analysis were calculated. The measurements were made in horizontal (supine) position, in orthostasis (the angle of 60 °) and again in supine position before and after enalapril (0.5 mg/kg b.w.), metipranolol (0.2 mg/kg b.w.), and after subsequent bilateral cervical vagotomy. The orthostasis in anaesthetized rabbits is accompanied by depression of respiratory rate reversed only by vagotomy. Furthermore, decrease of systemic blood pressure, unchanged heart rate and increased characteristics of heart rate variability were found, with predominant increase of spectral power in LF and VLF bands. This elevation can be eliminated only by complete blockade of ANS. Although the participation of ANS or RAA system in modification of individual HRV frequency bands is not as specific as in humans, we confirmed the participation of RAA system in determination of the VLF band.

Mechanical Condition Monitoring of Vacuum Circuit Breakers Using Artificial Neural Network

Using the Vibration signatures obtained during the operations as the original data, a mechanical condition monitoring method for vacuum circuit breaker is developed in this paper. The method coined the time-frequency analysis and the condition recognition based on artificial neural network. During preprocessing, the vibration signature was decomposed into individual frequency bands using the arithmetic of wavelet packets. The signal energy in the main frequency bands was used to form the condition feature vector, which was input to the artificial neural network for condition recognition. By introducing the parameter of approximation degree, a new recognition arithmetic based on Radial Basis Function was constructed. This approach could not only distinguish these conditions that belong to different known condition modes but also distinguish new condition modes.

LC共振型磁気マーカを用いた高精度位置検出システム

A precision position-detecting system using a wireless LC resonant magnetic marker was developed. The marker consists of an inductor and a capacitor without battery or electric wires, driven wirelessly by electromagnetic induction. The positional accuracy is less than 1 mm within 150 mm of the pickup coil array. The optimal design made it possible to improve the positional accuracy of the system. The system can be used for highly accurate motion-capturing without magnetic shielding because it is free from the earth's field. In addition, it has the potential to capture multi-point motion because it allows the markers to have individual frequency bands.

Wireless motion capture system using magnetically coupled LC resonant marker

A novel motion capture system using magnetically coupled LC resonant marker have been developed. This system composed from the LC marker, a driving coil and a pickup coil array. The marker consists only of an inductor and a capacitor without battery or electric wires, and driven wirelessly by the action of electromagnetic induction. The position accuracy was around 2 mm when the marker was located within the space of 50 mm apart from the pickup coil array. The system is applicable for highly accurate motion capturing without magnetic shielding because the system is free from the earth field. Additionally, it has a possibility of a multi-point motion capturing because the system allow markers to have an individual frequency band.

METHODS OF FREQUENCY ANALYSIS OF A COMPLEX MAMMALIAN VOCALISATION

ABSTRACT The prevalence of complex acoustic structures in mammalian vocalisations can make it difficult to quantify frequency characteristics. We describe two methods developed for the frequency analysis of a complex swift fox Vulpes velox vocalisation, the barking sequence: (1) autocorrelation function analysis and (2) instantaneous frequency analysis. The autocorrelation function analysis results in an energy density spectrum of the signal's averaged amplitude and frequency information. This analysis was used for locating possible formant structures and quantifying the energy distribution of single barks in the barking sequence. The instantaneous frequency analysis is applied to individual continuous frequency bands and generates frequency contours with a resolution of a couple of Hertz. It was used to quantify frequency modulation and calculate average frequencies of harmonic bands in individual barks and to estimate fundamental frequencies. This second method of analysis had to be evaluated with spectrographic analysis to gauge its reliability for each band analysed. The algorithms used should make both of these methods applicable to other complex vocalisations.

Sub-band SNR estimation using auditory feature processing

In this paper a new approach is presented for estimating the long-term speech-to-noise ratio (SNR) in individual frequency bands that is based on methods known from automatic speech recognition (ASR). It uses a model of auditory perception as front end, physiologically and psychoacoustically motivated sigma–pi cells as secondary features, and a linear or non-linear neural network as classifier. A non-linear neural network back end is capable of estimating the SNR in time segments of 1 s with a root-mean-square error of 5.68 dB on unknown test material. This performance is obtained on a large set of natural types of noise, containing instationary signals and alarm sounds. However, the SNR estimation works best for more stationary types of noise. The individual components of the estimation algorithms are examined with respect to their importance for the estimation accuracy. The algorithm presented in this paper yields similar or better results with comparable computational effort relative to other methods known from the literature for short-term SNR estimation. The new approach is purely based on slow spectro-temporal modulations and is therefore a valuable contribution to both, digital hearing-aids and ASR systems.

Method for RMS and power measurements based on the wavelet packet transform

The study provides the theoretical basis for the use of the wavelet packet transform (WPT) method for RMS and power/energy measurements. The proposed method can simultaneously measure the distribution of RMS quantities and power with respect to individual frequency bands directly from the wavelet transform coefficients associated with the concurrent voltage-current pair. Their dependent quantities such as power factor and total harmonic band distortion can also be calculated. Uniform frequency bands result from the WPT decomposition of power system waveforms and can be used for identification of bands of harmonics. The frequency bands also retain both the time and frequency relationship of the original waveforms, which is one of the major benefits provided by this method. The method is evaluated by its application to both simulated and actual power system waveforms.

Rms and Power Measurements: A Wavelet Packet Transform Approach

This study provides the theoretical basis for the use of wavelet packet transform (WPT) approach for root mean square (rms) and power/energy measurements. The proposed approach can simultaneously measure the distribution of the rms and power with respect to individual frequency bands directly from the wavelet transform coefficients (WTCs) associated with concurrent voltage current pair. Their dependent quantities such as power factor and total harmonic band distortion can be calculated as well. Uniform frequency bands are yielded from the WPT decomposition process of power system waveforms and can be used for identification of harmonic components. The frequency bands also retain both the time and frequency relationship of the original waveforms, which is one of the major benefits provided by this approach. The approach is evaluated by its application to both analytical and actual power system waveforms.

Mutual dependence of the octave-band weights in predicting speech intelligibility

Current objective measures for predicting the intelligibility of speech by an index assume that this can be obtained by simple addition of the contributions of individual frequency bands. The Articulation Index (AI, and the related Speech Intelligibility Index) and the Speech Transmission Index (STI) are based on this assumption. There is evidence that the underlying assumption of additive (mutually independent) contributions from a number of frequency bands is not optimal and may lead to erroneous prediction of the intelligibility for conditions with a limited or with a discontiguous frequency transfer. Depending on the frequency band considered, errors between 0.1 and 0.25 STI may occur. An experiment was designed to estimate the contribution of individual frequency bands, and their mutual dependence. For this purpose the speech spectrum was subdivided into seven octave bands with center frequencies ranging from 125 Hz to 8 kHz. For 26 different combinations of three or more octave bands, the Consonant–Vowel–Consonant-word score (CVC, nonsense words) was determined at three signal-to-noise ratios. It was found that successful prediction of the scores required a revised model which accounts for mutual dependency between adjacent octave bands. In this model a so-called redundancy correction is introduced. Consequences for the existing objective measures are discussed. The presented results are included in the revised IEC standard (IEC 60268-part 16, 1988).

A new tool for measuring the suckling stimulus during breastfeeding in humans: the orokinetogram and the Fourier series.

The Fourier series was used to analyse the oral movements recorded by the orokinetogram during breastfeeding in human babies. This is a new method that allows recording of oral movements without introducing any extrinsic element between the nipple and the mouth of the baby. The advantage of displaying suckling activity after fast Fourier transform (FFT) is that this algorithm allows storage, quantification and frequency analysis of the oral movements throughout a suckling bout, which enables the total oral activity to be measured. Two types of oral movements are found: slow high amplitude (SHA) and fast low amplitude (FLA). FLA movements may be derived from peristaltic movements of the tongue that result in tickling stimuli to the mechanoreceptors of the nipple and milk expression. The frequency bandwidth of oral movements is wider (0-8 Hz) than has been described previously (0-3 Hz) and this is due to the presence of the FLA oral movements. An indirect measurement of the energy of oral movements during suckling is obtained by the pattern of energy distribution used in each individual frequency band by oral movements. This pattern changes in relation to the periods of continuous and intermittent suckling activity. SHA and FLA oral movements are more intense during continuous suckling. Statistical analysis showed a correlation between the energy of SHA and FLA waves throughout the suckling bout, and also that the highest level of energy during suckling activity is displayed during the first 2 min. The novel tools described in this paper allow investigation of the role of suckling stimulus in reflex hormone release and other mother-infant interactions.

Spatial filtering and neocortical dynamics: estimates of EEG coherence.

The spatial statistics of scalp electroencephalogram (EEG) are usually presented as coherence in individual frequency bands. These coherences result both from correlations among neocortical sources and volume conduction through the tissues of the head. The scalp EEG is spatially low-pass filtered by the poorly conducting skull, introducing artificial correlation between the electrodes. A four concentric spheres (brain, CSF, skull, and scalp) model of the head and stochastic field theory are used here to derive an analytic estimate of the coherence at scalp electrodes due to volume conduction of uncorrelated source activity, predicting that electrodes within 10-12 cm can appear correlated. The surface Laplacian estimate of cortical surface potentials spatially bandpass filters the scalp potentials reducing this artificial coherence due to volume conduction. Examination of EEG data confirms that the coherence estimates from raw scalp potentials and Laplacians are sensitive to different spatial bandwidths and should be used in parallel in studies of neocortical dynamic function.

Noise Transmission Through a Vehicle Side Window Due to Turbulent Boundary Layer Excitation

This paper presents results of an investigation on noise transmission through an aluminum panel clamped to a greenhouse vehicle model subject to random acoustics, random vibration, and turbulent boundary layer excitations. Experiments on random acoustics and random vibration excitations were carried out in a reverberation chamber, and those on turbulent boundary layer excitation were conducted in the wind tunnel at the Chrysler Technology Center. The transmitted noise spectra were also calculated using a single computer program VibroAcoustic Payload Environment Prediction System (VAPEPS) based on Statistic Energy Analysis (SEA). The acoustic absorption coefficient (AAC) and the damping loss factor (DLF) for the vehicle were determined based on experimental data. Results showed that the largest differences between the measured and calculated sound pressure levels in any frequency band above 500 Hz were less than 2.5 dB for random acoustics excitation, 5.0 dB for random vibration excitation, and 5 dB for turbulent boundary layer excitation. In spite of the presence of differences in individual frequency bands, the calculated total sound pressure levels compared well with the measured ones. The differences between the calculated and measured total sound pressure levels were 0.7 dB for random acoustics excitation, 0.4 dB for random vibration excitation, and 1.8 dB for turbulent boundary layer excitation.

Mutual dependence of octave‐band contributions to speech intelligibility

Current objective measures for predicting the intelligibility of speech assume that this can be modeled as a simple addition of the contributions from individual frequency bands. The articulation index (Al) and speech transmission index (STI) are based on this assumption. There is evidence that the underlying assumption of mutually independent contributions is not valid and may lead to erroneous prediction for conditions with a limited frequency transfer, with spectral gaps or with spectrally localized masking. An experiment was performed focused on the contributions from individual frequency bands. For this purpose the speech signal was subdivided into 7 octave bands with center frequencies ranging from 125 Hz to 8 kHz. For 26 different combinations of 3 or more octave bands the CVC‐word score (consonant–vowel–consonant, nonsense words) was obtained at three signal‐to‐noise ratio. For an improved prediction of the observed intelligibility, a revised model was designed that accounts for mutual dependency ...

Distribution of sound levels for consonants and vowels within individual frequency bands

While it has been long known that vowels are, in general, more intense than consonants in naturally spoken speech, this statement is based upon the overall sound levels of the phonemes. The purpose of the present study was to determine the sound levels of consonants and vowels within individual frequency bands, with potential application to the provision of consonant audibility to hearing-impaired patients via amplification. The NST speech materials were digitized and subjected to 1/3 octave-band analysis in contiguous 23-ms samples. The samples were then classified as vowels or consonants, based upon waveform and spectral analysis. A large majority of the samples were vowels, reflecting their greater duration. The long-term consonant spectrum was flat, in contrast to the more familiar low-pass shape of the traditional speech spectrum. In the higher-frequency bands, consonant levels were in many cases more intense than the vowels. [Work supported by NIDCD Grant No. 00377.]

Electroencephalographic findings in dementia diseases

Even if generally the EEG cannot yield specific pointers that are typical for a special pattern of dementia, it is nevertheless meaningful and helpful to perform routine EEG in demented patients. EEG is the functional additional examination that does not place any stress on the patient and is easy to perform at a low cost (1). As a functional diagram the EEG reflects the electrical processes taking place in the cerebral cortex, yielding an excellent image of the cerebral functional state. Assessment of the EEG is done in accordance with internationally standardised criteria. Particular attention is directed at a slowing-down of the background activity, the occurrence and extent of scattered theta and delta waves, their topographical distribution and the development of pathological EEG characteristics during recording (44). Update spectral analysis EEG procedures, i.g. the possibility to calculate power spectra for the individual EEG frequency bands and their topographic distribution, it may be possible in the near future to further improve differentiation between normal and pathological EEG findings. The functional dynamic aspect of the EEG is its particularly strong point in the differential diagnostic clarification of dementia patterns. By repeated EEG recordings, i.e. by close follow-up, and by relating the electrophysiological findings to the clinical pattern, reliable pointers are obtained for the extent of the activity of the process underlying the dementia pattern. EEG is predestined like no other method to enable early detection of rapid changes in cerebral function thanks to its easy operation and unlimited repeatability. The occurrence of parenrhythmic theta and delta waves in the EEG reflects in a special manner the acuity of an organic basic process. In this way EEG enables differentiation between acute and chronic processes of cerebral damage. Over and above this, correlation with the relevant clinical findings makes it possible to differentiate between reversible states of dementia and irreversible defect syndromes and hence also to point to the long-term outcome. Finally, the occurrence of certain patterns of findings or the identification of characteristic wave forms allows essential differential diagnostic pointers and definitions.

An investigation of wall-layer dynamics using a combined temporal filtering and correlation

The relative role of outer- and wall-layer structures in the dynamics of the near-wall region of a turbulent boundary layer was explored by examining the scaling of the spanwise correlation coefficient between the wall shear stress and the streamwise velocity fluctuation, RTu(z), within narrow frequency bands spanning the entire turbulence spectrum. The scaling characteristics of RTu( z) within the individual frequency bands indicate that one can separate the contribution to the streamwise velocity fluctuations, in the buffer and logarithmic regions, due to outer-layer structures from those due to wall-layer events. Results provide insight into the lack of wall scaling for the conventional correlation coefficient, RTU(z), in the near-wall region. Moreover, the ‘negative dip’ in R,,(x+), which has often been associated with the low-speed streaks, was found to exist within certain frequency bands for all Reynolds numbers investigated (1579 < Re, < 5961). More interestingly, it is shown that, although the energy of the outer-layer structures increases with Reynolds number to overwhelm the streamwise velocity fluctuations in the near-wall region, the production of the Reynolds shear stress is dominated by wall-layer eddies. The findings of the current investigation provide strong support for Townsend’s hypothesis of ‘active’ and ‘inactive ’ motions.

Effects of remoxipride, a dopamine D-2 antagonist antipsychotic, on sleep-waking patterns and EEG activity in rats and rabbits.

The antipsychotic remoxipride, a selective dopamine D-2 receptor antagonist, was studied for its effects on sleep-waking patterns in the rat and electroencephalographic (EEG) activity in the rabbit. Haloperidol, which has lesser selectivity for D-2 receptors, was used for comparison. In the rat, remoxipride (1-10 mg/kg SC) did not affect either total sleep or non-rapid eye movement (non-REM) sleep. Only REM was slightly reduced by the high dose of 10 mg/kg. Haloperidol (0.1-1 mg/kg PO) enhanced duration of both total sleep and non-REM sleep. In the rabbit, remoxipride (3 and 10 mg/kg IV) induced no significant changes of the EEG power spectrum over 0.1-38.5 Hz or individual frequency bands. In both cortex and hippocampus the drug did not alter the arousal response to acoustic sensory stimuli. Plasma concentration of remoxipride 10 mg/kg IV in rabbits declined biexponentially and was 4 and 2 mumol/l at 30 min and 1 h, respectively. Haloperidol (0.3 and 1 mg/kg) slowed down the EEG activity, enhanced the power spectrum of the cortical and hippocampal activity, and significantly reduced the duration of arousal induced by sensory stimuli. The results indicate that, unlike haloperidol, remoxipride has weak or no sedative effects. The data also provide support to the notion that D-2 receptors are not involved in the regulation of states of sleep and sedation.

Prediction of Transient Vibration Envelopes Using Statistical Energy Analysis Techniques

The prediction, by the statistical energy analysis (SEA) method, of transient vibration envelopes for coupled systems is investigated. The relation between the time-varying energy transferred between two coupled subsystems and time-varying energies of the subsystems is studied numerically and experimentally. These studies indicate that time-varying energy transmitted between two subsystems is related to the subsystem energies by an apparent time-varying coupling loss factor. It is shown that the apparent coupling loss factor approaches the asymptotic (or steady-state) coupling loss factor as response energies and transferred energies are integrated over progressively larger times. Both the apparent time-varying coupling loss factor and the asymptotic coupling loss factor, determined experimentally, are used in energy balance equations to predict the time-varying vibration envelopes of a system of two point-coupled plates and the results are compared. Although overall response predictions are similar, considerable differences are noted in individual frequency bands. However, no general method for a priori determination of the apparent time-varying coupling loss factor is suggested.