- Email: [email protected]
Application of exposure criteria to different types of industrial ultrasound
Ultrasonics International 87 abstracts in size and position of the focus from the low-power case. Results are given.
Location of kidney-stones for non-invasive piezoelectric lithotripsy (Piezo- ESWL)
F. Ueberle, University of Karlsruhe, FRG A piezoelectric transducer as a high energy source for non-invasive lithotripsy allows the use of the same transducer as a high-resolution device for the fine-location of the kidney-stone. In this paper the special properties of the location method are presented. The focussing of the transducers, methods for the ultrasonic coarse- and fine-location of kidney and kidney-stone and the special problems of the ultrasonic location in combination with high-energy ultrasonic pulses on destruction purpose are discussed.
fact that underwater noise is due to a broad variety of different sources. In one region of the spectrum one or more of these sources will dominate over the others and sources of ambient noise in the sea at frequencies above 1 5 - 2 0 kHz are the main topic of this invited tutorial lecture. Underwater ambient noise sources are either natural or man-made. Among the natural sources shall in particular be mentioned the breaking of surface waves being closely related to the wind speed where spray, splashes and the dynamic of trapped micro bubbles for instance contribute to the noise level at higher frequencies. Moreover, natural high-frequency noise sources like turbulent flow, rain, ice, biological activities and at high frequencies also thermal effects shall be discussed. Of man-made sources of noise at ultrasonic frequencies shall be emphasized ship traffic leading to for instance cavitation noise, off-shore activities like oil prospecting and production, and underwater explosions. Mechanisms of noise generation, spectral characteristics, geographical locations and individual features related to various sources of underwater ultrasound will be presented and discussed.
Application of exposure criteria to different types of industrial ultrasound
K. Korpert and R. Vanek, AIIgemeine Unfallversicherungsanstalt, Wien, Austria Frequency dependent exposure criteria, as e.g. that of Acton, are widly used to estimate the hazards due to industrial ultrasound. In a series of measurement results it will be shown, that: •
they are sometimes only of poor value for discrete US-spectra, • they are not applicable for continuous US-spectra, • the AU-weighted sound pressure level, in combination with a limiting value, seems to be suited for the estimation of hearing damage risk.
Nondestructive approach for analysing the germinability of acorns
V. Bucur and C. Muller, Centre de Recherches Forestieres de NANCY, France A novel application of ultrasonic velocity method is proposed for the prediction of the germinability of acorns, based on morphological criteria (dimensions of two axes) and physical criteria (density, ultrasonic velocity, impedance and acoustic stiffness). All specimens were six months old, of a good trading quality, but characterised by a high ratio (50 pc) of unviable acorns. Experimental advances have been accomplished in the obtaining of acoustical parameters able to predict the germinability, using principal-components statistical analysis. The fitness to germination is related to density, and ultrasonic velocity. A strong density and a high ultrasonic velocity characterise a viable acorn.
Underwater
acoustics
Sources of underwater ultrasound (Invited)
L. Bjomo, Technical University of Denmark, L yngby, Denmark Noise data in the sea acquired over the years show that ambient noise has different characteristics at different frequencies. These observations are particularly based on the
Numerical models of sound propagation in inhomogeneous media (Invited)
F.B. Jensen, SACLANT ASW Research Centre, Italy Over the past 10 years considerable progress has been done in developing computationally efficient numerical models of sound propagation in media with 1 - D or 2- D spatial inhomogeneity, while it is still not feasible to solve general 3-D acoustic problems. The class of problems with 1 -D inhomogeneity is characterised by separability of the wave equation, and commonly solved by means of normal modes or Fourier integral techniques. An example of a separable problem is a waveguide (duct) with the sound speed changing only in the transverse direction. The 2-D non-separable problems are of more general interest, and they can be solved exactly by coupled normal modes or approximately by parabolic equation techniques. The above wave-theory techniques for solving 1 -D and 2-D propagation problems will be described in detail, and their applicability will be illustrated by solving fundamental wave propagation problems, not tractable by analytical methods, from the fields of underwater acoustics, seismics, and ultrasonics. In particular, we shall look at ducted propagation in the ocean over sloping bottoms, propagation of seismic interface waves along the sea floor, ultrasonic beam reflection from layered fluid/solid structures (leaky Rayleigh waves), and beam focusing by a thick acoustic lens.
Synthetic aperture sonar
A.S. Gida and J.W.R. Griffiths, University of Technology, Loughborough, UK This paper will describe some recent work on the use of the synthetic aperture technique for 2 dimensional underwater imaging, i.e., range versus bearing or elevation. The sonar system comprises a transmitter producing a digitally controlled and generated waveform and a receiver which measures the phase and amplitude of the receiver signal. The transducer array is positioned under computer control and the phase and amplitude data from the receiver is stored in the computer for processing. Although the computer is a fairly simple micro-computer the addition of a 32016 second processor allows fairly fast processing of the data for reconstruction of the image. Extensive trials have been successfully carried out in a large sonar tank in the department and more recently a new
Ultrasonics 1987 Vol 25 November
349
Location of kidney-stones for non-invasive piezoelectric lithotripsy (Piezo- ESWL)
F. Ueberle, University of Karlsruhe, FRG A piezoelectric transducer as a high energy source for non-invasive lithotripsy allows the use of the same transducer as a high-resolution device for the fine-location of the kidney-stone. In this paper the special properties of the location method are presented. The focussing of the transducers, methods for the ultrasonic coarse- and fine-location of kidney and kidney-stone and the special problems of the ultrasonic location in combination with high-energy ultrasonic pulses on destruction purpose are discussed.
fact that underwater noise is due to a broad variety of different sources. In one region of the spectrum one or more of these sources will dominate over the others and sources of ambient noise in the sea at frequencies above 1 5 - 2 0 kHz are the main topic of this invited tutorial lecture. Underwater ambient noise sources are either natural or man-made. Among the natural sources shall in particular be mentioned the breaking of surface waves being closely related to the wind speed where spray, splashes and the dynamic of trapped micro bubbles for instance contribute to the noise level at higher frequencies. Moreover, natural high-frequency noise sources like turbulent flow, rain, ice, biological activities and at high frequencies also thermal effects shall be discussed. Of man-made sources of noise at ultrasonic frequencies shall be emphasized ship traffic leading to for instance cavitation noise, off-shore activities like oil prospecting and production, and underwater explosions. Mechanisms of noise generation, spectral characteristics, geographical locations and individual features related to various sources of underwater ultrasound will be presented and discussed.
Application of exposure criteria to different types of industrial ultrasound
K. Korpert and R. Vanek, AIIgemeine Unfallversicherungsanstalt, Wien, Austria Frequency dependent exposure criteria, as e.g. that of Acton, are widly used to estimate the hazards due to industrial ultrasound. In a series of measurement results it will be shown, that: •
they are sometimes only of poor value for discrete US-spectra, • they are not applicable for continuous US-spectra, • the AU-weighted sound pressure level, in combination with a limiting value, seems to be suited for the estimation of hearing damage risk.
Nondestructive approach for analysing the germinability of acorns
V. Bucur and C. Muller, Centre de Recherches Forestieres de NANCY, France A novel application of ultrasonic velocity method is proposed for the prediction of the germinability of acorns, based on morphological criteria (dimensions of two axes) and physical criteria (density, ultrasonic velocity, impedance and acoustic stiffness). All specimens were six months old, of a good trading quality, but characterised by a high ratio (50 pc) of unviable acorns. Experimental advances have been accomplished in the obtaining of acoustical parameters able to predict the germinability, using principal-components statistical analysis. The fitness to germination is related to density, and ultrasonic velocity. A strong density and a high ultrasonic velocity characterise a viable acorn.
Underwater
acoustics
Sources of underwater ultrasound (Invited)
L. Bjomo, Technical University of Denmark, L yngby, Denmark Noise data in the sea acquired over the years show that ambient noise has different characteristics at different frequencies. These observations are particularly based on the
Numerical models of sound propagation in inhomogeneous media (Invited)
F.B. Jensen, SACLANT ASW Research Centre, Italy Over the past 10 years considerable progress has been done in developing computationally efficient numerical models of sound propagation in media with 1 - D or 2- D spatial inhomogeneity, while it is still not feasible to solve general 3-D acoustic problems. The class of problems with 1 -D inhomogeneity is characterised by separability of the wave equation, and commonly solved by means of normal modes or Fourier integral techniques. An example of a separable problem is a waveguide (duct) with the sound speed changing only in the transverse direction. The 2-D non-separable problems are of more general interest, and they can be solved exactly by coupled normal modes or approximately by parabolic equation techniques. The above wave-theory techniques for solving 1 -D and 2-D propagation problems will be described in detail, and their applicability will be illustrated by solving fundamental wave propagation problems, not tractable by analytical methods, from the fields of underwater acoustics, seismics, and ultrasonics. In particular, we shall look at ducted propagation in the ocean over sloping bottoms, propagation of seismic interface waves along the sea floor, ultrasonic beam reflection from layered fluid/solid structures (leaky Rayleigh waves), and beam focusing by a thick acoustic lens.
Synthetic aperture sonar
A.S. Gida and J.W.R. Griffiths, University of Technology, Loughborough, UK This paper will describe some recent work on the use of the synthetic aperture technique for 2 dimensional underwater imaging, i.e., range versus bearing or elevation. The sonar system comprises a transmitter producing a digitally controlled and generated waveform and a receiver which measures the phase and amplitude of the receiver signal. The transducer array is positioned under computer control and the phase and amplitude data from the receiver is stored in the computer for processing. Although the computer is a fairly simple micro-computer the addition of a 32016 second processor allows fairly fast processing of the data for reconstruction of the image. Extensive trials have been successfully carried out in a large sonar tank in the department and more recently a new
Ultrasonics 1987 Vol 25 November
349