Showing papers on "Acoustic source localization published in 1970"
TL;DR: In this article, the rotor-stator interaction was studied theoretically, taking into account the effect of compressibility of fluid and the non-compact source distribution over the blades.
95 citations
01 Nov 1970
TL;DR: In this paper, a wave model is used for the investigation of sound generation in circular jets, where the source term of the Lighthill equation is expressed by a Fourier series in the azimuthal angle, is Fourier-transformed with respect to time, and each component is assumed to be of wave-type in jet direction.
Abstract: A wave model is used for the investigation of sound generation in circular jets. The source term of the Lighthill equation is expressed by a Fourier series in the azimuthal angle, is Fourier-transformed with respect to time, and each component is assumed to be of wave-type in jet direction. A far-field solution for the sound pressure is derived in this way for single azimuth-frequency components. It is found that the sound field depends strongly on a convection parameter and on a jet thickness parameter. The influence of axisymmetric and azimuthal source components is discussed. For a special source term with arbitrarily chosen amplitude distribution the convection factor and the jet thickness factor of sound intensity are calculated and discussed. The influence of the amplitude distribution of the source components is found to be of minor importance.
37 citations
Patent•
10 Sep 1970
TL;DR: In this paper, the outputs of two nominally identical oscillators constructed using non-precision components which cause them to have slightly different output frequencies were added to simulate the sounds made by a jet engine.
Abstract: Sound generation apparatus to simulate the sounds made by a jet engine. By adding the outputs of two nominally identical oscillators constructed using non-precision components which cause them to have slightly different output frequencies a sound closely simulating whine is obtained. Amplitude of sound is controlled by the use of field effect transistor shunts which have applied to their gates signals representing the parameters which affect the level of sound heard by a listener.
14 citations
05 Mar 1970
TL;DR: In this article, a coherent monochromatic light beam is directed into a lightsound interaction cell in which a spatially modulated sound field of constant frequency-carrying image information is propagated nominally transversely to the beam by means of a transducer attached to the sound cell and driven by an appropriate constant frequency signal.
Abstract: A coherent monochromatic light beam is directed into a lightsound interaction cell in which a spatially modulated sound field of constant frequency-carrying image information is propagated nominally transversely to the beam by means of a transducer attached to the sound cell and driven by an appropriate constant frequency signal. The beam is focused about any desired point in the sound field so that a scattering interaction is obtained. The focal region is maintained narrower than the sound wavelength so that a temporal and spatial modulation is imparted to the light representative of the phase and amplitude of the sound field at the focal region. Interposed in the path of such modulated light is a photodetector preceded by a demodulator comprised of either a spatial filter or quarter-waveplate and analyzer. The photodetector extracts an output signal at the sound frequency whose phase and amplitude is representative of that of the sound field about the desired focal region. Such a signal may be recorded or displayed either conventionally, or holographically, if the output signal is mixed with a reference signal derived from the constant frequency transducer signal.
10 citations
Patent•
29 Jun 1970
TL;DR: In this article, a device for measuring and displaying four different acoustic quantities in a fluid medium is presented, i.e., acoustic pressure, particle acceleration, acoustic impedance, and acoustic power density.
Abstract: A device for measuring and displaying four different acoustic quantities in a fluid medium. The specific acoustic quantities are: acoustic pressure; particle acceleration; acoustic impedance; and acoustic power density. All of these quantities are determined simultaneously and each is instantly displayed as a function of the driving frequency of an excitation source in the fluid medium.
8 citations
TL;DR: In this paper, the authors investigate sound transmission properties in relation to the conditions of medium excitation by both the primary and the secondary sound sources in a plane wave acoustic pressure field and in a direct wave field.
6 citations
4 citations
3 citations
3 citations
TL;DR: The work of Dyer as mentioned in this paper was extended to derive expressions for the sound pressure cross spectrum and cross correlation within a hard circular duct and with arbitrary boundary conditions, where the internal impedance concept was used to account for the source end boundary condition.
Abstract: The work of Dyer [J. Acoust. Soc. Amer. 30, 833–841 (1958)] was extended to derive expressions for the sound pressure cross spectrum and cross correlation within a hard circular duct and with arbitrary boundary conditions. Results are expressed either in terms of a source plane pressure cross spectrum or in terms of a modal spectral distribution. An internal impedance concept was used to account for the source end boundary condition. Reflected waves are included, the termination being specified by a local impedance. In order to estimate sound power from pressure cross‐correlation measurements in the cross‐mode region, programs were written to compute the exact sound power and the error of the estimate by use of the plane‐wave formula for given measuring positions, given modal spectra, and given modal correlation. Depending on the type of source, optimum measuring positions were determined. Methods to measure modal spectra of a certain source were developed. [Essential support of this work was given by Air Conditioning and Refrigeration Institute.]
1 citations
TL;DR: In this article, the authors considered the case where the thickness of each layer is small compared with the wave-length and the value for sound velocity becomes that usually expected for a homogeneous compressible medium.
Abstract: Pressure propagation phenomena in regularly spaced two-phase layers is discussed from theory. The value for sound velocity becomes that usually expected for a homogeneous compressible medium in the limiting case where the thickness of each layer is small compared with the wave-length. There must be a sufficient number of layers for the homogeneous concept to hold. Otherwise dispersion is expected.
01 Jan 1970
TL;DR: Results have illustrated that the proposed Bayesian method outperforms both that of the Microsoft Kinect sensor and the trigonometric approach in terms of classification accuracy.
Abstract: The goal of this study is to equip a mobile service robot with an ability to navigate to the human who commands the robot by speech. Based on time delay of arrival (TDOA) features, a Bayesian approach to sound source direction estimation is proposed. The method requires low computational complexity and is feasible for real-time robot navigation. Based on an experiment with various parameter settings in an indoor environment, different factors that affect the classification accuracy have been analyzed. The experiment results have illustrated that the proposed Bayesian method outperforms both that of the Microsoft Kinect sensor and the trigonometric approach in terms of classification accuracy.