Acoustics – Geophysical or subsurface exploration – Well logging
Patent
1998-10-08
2000-06-20
Witkowski, Stanley J.
Acoustics
Geophysical or subsurface exploration
Well logging
181102, 181101, 181108, 181110, 181117, 181113, 181119, 181120, 367155, 367157, 367158, 367160, 367161, 367168, 367153, 367159, 367140, 367141, G01V 140
Patent
active
060766298
DESCRIPTION:
BRIEF SUMMARY
This invention relates in general to acoustic sources for the generation of soundwaves in water, especially soundwaves with low frequencies, e.g. for use in seismic studies at sea. Such sources, being used in generating soundwaves in water, may be described in different ways, such as seismic emitters, flextensional sources or acoustic vibrators, such as sonars.
The acoustic source according to the invention may preferably be used in relation to such sound- or tone-emitters, since the soundwaves emitted into the water may be reflected from the sea bottom and geological formations beneath it, with succeeding monitoring and detection using hydrophones or geophones of different types.
The invention is especially aimed at a certain embodiment of sound emitting membranes or shells in acoustic sources, and the present embodiment may be considered to be related to certain types of flextensional emitters.
Flextensional emitters are described in many publications, one example being L. H. Royster: "The flextensional concept. A new approach to the design of underwater acoustic transducers", Appl.Acoust. 3 (1970), pp 117-226. Other examples are G. Bromfield: "Class IV flextensional transducers", Proceedings Second International Workshop on Power Transducers, Toulon, (France) June 1990, and G. Brigham and B. Glass: "Present status in flextensional transducer technology", J. Acoust. Soc. A., 68(1980), pp. 1046-1052.
Most flextensional shells are based on the principle of changes in volume in a vibrating, elliptic shell. When the long axis of an ellipse is set into vibration the length of the short axis will also vibrate, but with a much larger amplitude. This makes the ellipse shape an effective generator of acoustic energy at low frequencies. Generally the basic resonance frequency of the elliptic shell is so low that the length of the shell is small when compared to the wavelength in water.
A limiting factor for this kind of shells are the mechanical tensions forced upon the shell when large vibrational amplitudes are to be obtained. Normally aluminum or glass-fibre armed plastic is used as shell material. The use of such shells are also limited as a result of their complex shape, which lead to complicated manufacturing methods.
A special example of a complicated shape, being visually and functionally different from the abovementioned elliptic, round shells (egg-shaped), are hyperbolic, round shells. The advantage with this shape is that the short axis will vibrate in face with the long axis. An embodiment based on this principle is described in D. F. Jones and C. G. Reithmeier: "Low frequency barrel-stave projectors" (Proceedings UDT 93, Nice, France, Microwave Exh. & Pub. Ltd. 1993, pp 251-253).
This last embodiment comprises in short two octagonal end plates joined together with eight rod-shaped elements having a concave curvature and being positioned in an essentially circular or polygonal arrangement surrounding an axis of symmetry. A major problem with this design is the many slits between the rod elements, and the question of sealing and possible contact between these elements.
In Norwegian patent application no. 94.1708 (corresponding to International patent application no. PCT/NO95/00071) an acoustic source is described with sound emitting surfaces having a generally concave shape and being adapted to be set into vibrational movement using a drive assembly affecting the sound emitting surfaces through at least one pressure element and two platelike end parts being connected to the sound emitting surfaces. The novelty of this invention is primarily related to the fact that the sound emitting surfaces are formed by two curved membrane-like plate members having width and height dimensions of comparable sizes and being mounted back-to-back, that the plate-like end pieces have essentially rectangular shapes with a first pair of opposite side edges connected to the end parts of the plate members, and that another pair of side edges on each end piece, as well as the side edges of the plate members are connected to tw
REFERENCES:
patent: 4706230 (1987-11-01), Inoue et al.
patent: 4763307 (1988-08-01), Massa
patent: 4764907 (1988-08-01), Dahlstrom et al.
patent: 4862429 (1989-08-01), Rolt
patent: 4894811 (1990-01-01), Porzio
patent: 4932008 (1990-06-01), Rolt
patent: 4941202 (1990-07-01), Upton
patent: 5126979 (1992-06-01), Rowe, Jr. et al.
patent: 5375101 (1994-12-01), Wolfe et al.
patent: 5515343 (1996-05-01), Boucher et al.
patent: 5546361 (1996-08-01), Boucher et al.
Brigham, G. and Glass, B.: Present Status in Flextensional Transducer Technology. J. Acoust. Soc. Am., vol. 68, No. 4, Oct. 1980.
Martin Edgardo San
Unaco Systems AB
Witkowski Stanley J.
LandOfFree
Low frequency flextensional acoustic source for underwater use does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Low frequency flextensional acoustic source for underwater use, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Low frequency flextensional acoustic source for underwater use will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1843921