Digital-filter representation of the correction term for high-frequency zeros in the glottal-vocal-tract spectrum

1972 ◽  
Vol 8 (26) ◽  
pp. 643
Author(s):  
M.A. Nwachuku
Keyword(s):  
Digital Filter ◽  
High Frequency ◽  
Vocal Tract ◽  
Correction Term

An approximate method in high-frequency scattering

1962 ◽  
Vol 58 (4) ◽  
pp. 662-670
Author(s):  
A. Sharples
Keyword(s):  
Boundary Condition ◽  
Circular Cylinder ◽  
Integral Representation ◽  
Sound Wave ◽  
High Frequency ◽  
Correction Term ◽  
Scattering Coefficient ◽  
Extended Form ◽  
Geometrical Acoustics ◽  
Plane Sound

ABSTRACTThe diffraction of a high-frequency plane sound wave by a circular cylinder is investigated when the boundary condition on the cylinder is expressed by means of an equation of the form The special feature of this investigation is that an extended form of the Kirchhoff-Fresnel theory of diffraction is used to find an integral representation for the scattering coefficient. In order to avoid the complicated analysis which would be necessary to evaluate the integrals concerned, the more natural geometrical acoustics approach is used to find the first correction term in the scattering coefficient. Numerical results are given for large and small values of the impedance Z.

An improved solution to the fourth moment equation for intensity fluctuations

1983 ◽  
Vol 386 (1791) ◽  
pp. 461-474 ◽  
Keyword(s):  
High Frequency ◽  
Correction Term ◽  
Approximate Solutions ◽  
Moment Equation ◽  
Solution Procedure ◽  
Fourth Moment ◽  
Basic Solution ◽  
Numerical Work ◽  
First Order ◽  
First Order Correction

An approximate solution is presented for the fourth moment equation that describes fluctuations of intensity in a wave propagating through a randomly fluctuating medium. The solution is valid for high frequency or relatively strong fluctuations in the medium. The solution procedure is straightforward and at zero order agrees with previously derived approximate solutions. However, the present method is much more direct and more easily extended to complicated problems. Indeed, the first order correction to this basic solution is also determined and it is found that significantly better agreement with previous numerical work is obtained. In addition, knowledge of the correction term allows approximate estimates to be made for the error involved in using the basic solution.

scholarly journals The physiology of oral whistling: a combined radiographic and MRI analysis

2018 ◽  
Vol 124 (1) ◽  
pp. 34-39 ◽  
Author(s):  
Alba Azola ◽  
Jeffrey Palmer ◽  
Rachel Mulheren ◽  
Riccardo Hofer ◽  
Florian Fischmeister ◽  
...  
Keyword(s):  
High Frequency ◽  
Vocal Tract ◽  
Resonant Cavity ◽  
Helmholtz Resonator ◽  
Theoretical Models ◽  
Experimental Models ◽  
Air Jet ◽  
Tongue Position ◽  
Buccal Space ◽  
Opening And Closing

The fluid mechanics of whistling involve the instability of an air jet, resultant vortex rings, and the interaction of these rings with rigid boundaries (see http://www.canal-u.tv/video/cerimes/etude_radiocinematographique_d_un_siffleur_turc_de_kuskoy.13056 and Meyer J. Whistled Languages. Berlin, Germany: Springer, 2015, p. 74–774). Experimental models support the hypothesis that the sound in human whistling is generated by a Helmholtz resonator, suggesting that the oral cavity acts as a resonant chamber bounded by two orifices, posteriorly by raising the tongue to the hard palate, and anteriorly by pursed lips (Henrywood RH, Agarwal A. Phys Fluids 25: 107101, 2013). However, the detailed anatomical changes in the vocal tract and their relation to the frequencies generated have not been described in the literature. In this study, videofluoroscopic and simultaneous audio recordings were made of subjects whistling with the bilabial (i.e., “puckered lip”) technique. One whistling subject was also recorded, using magnetic resonance imaging. As predicted by theory, the frequency of sound generated decreased as the size of the resonant cavity increased; this relationship was preserved throughout various whistling tasks and was consistent across subjects. Changes in the size of the resonant cavity were primarily modulated by tongue position rather than jaw opening and closing. Additionally, when high-frequency notes were produced, lateral chambers formed in the buccal space. These results provide the first dynamic anatomical evidence concerning the acoustic production of human whistling. NEW & NOTEWORTHY We establish a new and much firmer quantitative and physiological footing to current theoretical models on human whistling. We also document a novel lateral airflow mechanism used by both of our participants to produce high-frequency notes.

scholarly journals The corpuscular X-ray spectra of the raio-elements

1933 ◽  
Vol 139 (838) ◽  
pp. 336-342 ◽  
Keyword(s):  
High Frequency ◽  
Photographic Plate ◽  
Correction Term ◽  
X Rays ◽  
X Ray ◽  
Points Of Interest ◽  
Electron Transitions ◽  
Different Types ◽  
Normal Atom ◽  
Narrow Bands

An interesting way in which an excited atom can emit its excess energy has been brought to light by the experiments of Robinson and of Auger. If, for example, an atom is ionised in the K state, then it may emit a quantum of radiation of some line of its K X-ray spectrum by means of a transition of an electron to the K level, but as an alternative method it may emit an electron instead, thus leaving the atom doubly ionised. One such process might be represented as [L I → K, L II → ∝] and the energy E of the ejected electron would be given by E = K abs — L Iabs — L IIabs — δ, where δ is a small correcting term to take into account that the work required to remove an electron from an ionised atom is slightly greater than that necessary in the case of a normal atom. Processes of this kind are essentially different from those giving rise to radiation since two electrons instead of one are concerned in the transition. The entire process must be considered as occurring simultaneously, and, to take as an example the case already mentioned, it has no meaning to attempt to state whether it is an L I electron which goes to the K state, and an L II electron which is ejected or vice versa . Two points of interest in this phenomenon are the investigation of the magnitude of the correction term δ, and of the relative probabilities of the different types of transition. It will be seen later that the possible transitions are considerably more numerous than with single electron transitions which give rise to radiation. This phenomenon has been studied by Robinson by analysing the ejected electrons with a magnetic field. A thin layer of the element under investigation is placed in the position of the source in the well-known semi-circular focussing apparatus, and is irradiated with X-rays of sufficiently high frequency to be able to eject electrons from the K state. There then follows a further electronic emission from these ionised atoms in the manner already described. Both sets of electrons are recorded photographically, and the various groups show up as lines or narrow bands on the photographic plate. A difficulty inherent in the nature of the experiment is that the groups of homogeneous electrons become slightly diffuse in emerging from the target which must have a certain thickness in order to yield groups of reasonable intensity.

scholarly journals An ampere meter for measuring alternating currents of very high frequency

1928 ◽  
Vol 121 (787) ◽  
pp. 41-71 ◽  
Keyword(s):  
High Frequency ◽  
Correction Term ◽  
Small Diameter ◽  
Great Difficulty ◽  
Very High Frequency ◽  
Steady Current ◽  
Heated Wire ◽  
Frequency Correction ◽  
Heated Element ◽  
Very High

The measurement of alternating currents of very high frequency in general presents great difficulty because all existing ammeters have a frequency correction which cannot be calculated. The dynamometer ammeter of ordinary construction is very satisfactory for currents whose frequency does not exceed a few hundred cycles per second, but is unsuitable for currents whose frequency is many kilocycles because the highly inductive winding presents an enormous impedance to the current and its presence in a circuit modifies completely the conditions obtaining therein. Further, the distribution of current over the cross section of the wire and the value of the current from turn to turn will alter with the frequency, with the result that a steady current calibration becomes invalid and the correcting factor cannot be calculated or even estimated roughly. So even if its presence can be tolerated in a circuit, such an instrument can be used only for relative measurements at one frequency and its indications cannot be reduced to absolute measure. The ammeters in general use are thermal instruments depending on the thermal expansion of a suitable element or on the production of a thermoelectric E. M. F. in a junction placed close to a wire heated by the high frequency current. In either system the resistance of the heated element depends on the frequency of the current which heats it and so a steady current calibration cannot be used indiscriminately. The necessary configuration of the heated element and its situation with respect to surrounding alternating magnetic fields usually renders impossible the calculation of its resistance. It is usual to make the heated wire of a high resistance material and with a small diameter so as to render the calibration sensibly constant up to a high value of frequency. If the calculated resistance of such a straight isolated wire at an assigned frequency has increased by only a small fraction of 1 per cent, above the steady current value, then it will seem reasonable to suppose that the calibration of the bent and unisolated heated wire is valid to at least 1 per cent, up to this frequency. For higher frequencies there will be a correction term whose value can be estimated only very roughly. To maintain the calibration, valid np to a frequency of some thousand kilocycles per second the heating wire must be so fine that it will not carry a current of more than, say, 1 ampere. To measure larger currents we are faced by the problem of providing a shunt which the shunting ratio is independent of frequency. Brief consideration will show it is very difficult to arrange a group of fine parallel wires so that each has precisely the same resistance, and further that the situation of each one is the same with respect to all the others and also the remainder of the circuit. If both conditions are not fulfilled the total current will not always divide equally among the component parallel paths and the calibration curve will be subject to a frequency correction. A common and successful method is to arrange the parallel wires as generators of a cylinder, double cone, or hyperboloid and to allow each wire to heat one of a group of thermocouples connected in series electrically.

scholarly journals Formants

2018 ◽  
Author(s):  
Daniel Aalto ◽  
Jarmo Malinen ◽  
Martti Vainio
Keyword(s):  
Digital Filter ◽  
Speech Processing ◽  
Vocal Tract ◽  
Acoustic Energy ◽  
Acoustic Properties ◽  
Spectral Envelope ◽  
Local Maxima ◽  
Place Of Articulation ◽  
Power Spectral ◽  
Children's Speech

Formant frequencies are the positions of the local maxima of the power spectral envelope of a sound signal. They arise from acoustic resonances of the vocal tract air column, and they provide substantial information about both consonants and vowels. In running speech, formants are crucial in signaling the movements with respect to place of articulation. Formants are normally defined as accumulations of acoustic energy estimated from the spectral envelope of a signal. However, not all such peaks can be related to resonances in the vocal tract, as they can be caused by the acoustic properties of the environment outside the vocal tract, and sometimes resonances are not seen in the spectrum. Such formants are called spurious and latent, respectively. By analogy, spectral maxima of synthesized speech are called formants, although they arise from a digital filter. Conversely, speech processing algorithms can detect formants in natural or synthetic speech by modeling its power spectral envelope using a digital filter. Such detection is most successful for male speech with a low fundamental frequency where many harmonic overtones excite each of the vocal tract resonances that lie at higher frequencies. For the same reason, reliable formant detection from females with high pitch or children’s speech is inherently difficult, and many algorithms fail to faithfully detect the formants corresponding to the lowest vocal tract resonant frequencies.

Application of Wavelet Digital Filter of Fourier Transform Profilometry in 3-D Measurement

2004 ◽  
Vol 471-472 ◽  
pp. 654-657
Author(s):  
Yun Shan Wang ◽  
S. Fu ◽  
Jin Quan Xu ◽  
Can Lin Zhou ◽  
S.C. Si ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Wavelet Transform ◽  
Digital Filter ◽  
High Frequency ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Fourier Transform Profilometry ◽  
Low Pass ◽  
Phase Demodulation

Fourier transform profilometry in 3-D measurement based on wavelet digital filter is presented in this paper. Before phase demodulation, original modulated grating image is handled with wavelet transform in order to remove the background components and high frequency. This method resolves spectrum overlapping at some extent and reduces the requirement of low-pass filter.

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