Method and apparatus for sensing underwater signals

Methods and apparatuses are disclosed that assist in sensing underwater signals in connection with geophysical surveys. One embodiment relates to a transducer including a cantilever coupled to a base. The cantilever may include a beam and a first coupling surface angularly oriented from the beam, and the base may include a second coupling surface angularly oriented from the beam and substantially parallel to the first coupling surface of the cantilever. The transducer may further include a sensing material coupled between the first coupling surface of the cantilever and the second coupling surface of the base.

TECHNICAL FIELD

This disclosure relates generally to transducers, and more particularly to transducers for use in sensing underwater signals such as acoustic signals.

BACKGROUND

Petrochemical products such as oil and gas are ubiquitous in society and can be found in everything from gasoline to children's toys. Because of this, the demand for oil and gas remains high. In order to meet this high demand, it is important to locate oil and gas reserves in the Earth. Scientists and engineers conduct “surveys” utilizing, among other things, seismic and other wave exploration techniques to find oil and gas reservoirs within the Earth. These seismic exploration techniques often include controlling the emission of seismic energy into the Earth with a seismic source of energy (e.g., dynamite, air guns, vibrators, etc.), and monitoring the Earth's response to the seismic source with one or more receivers (which may each include one or more transducers used as sensors, for example, an accelerometer, a hydrophone, etc.). By observing the reflected seismic signals detected by the receiver during the survey, the geophysical data pertaining to reflected signals may be acquired and these signals may be used to form an image indicating the composition of the Earth near the survey location.

Conventional receivers may include one or more transducers used as accelerometers to measure vibrations, particle motion, acceleration, and so forth. For example, a 3-dimensional receiver may include three orthogonally oriented transducers. Each transducer may include a flexible cantilever beam and one or more piezoelectric elements bonded to the beam, as well as a proof mass attached to one end of the beam. When forces are exerted on the proof mass, the proof mass and the attached cantilever beam are deflected, causing stress of the piezoelectric elements. This stress of the piezoelectric elements results in a measurable change in the electric charge or voltage generated by the piezoelectric material forming the elements, which can be measured to determine the direction and magnitude of the deflection of the proof mass. The typical voltage output may be from several mV to hundreds of mV.

Conventional transducer designs often utilize piezoelectric material that is best suited for sensing normal stress imparted onto the piezoelectric material. Such material is well-suited to detecting some signals, but may be less efficient at detecting other signals, such as low-level signals which may be desirable to detect during seismic imaging. Accordingly, transducers that allow for detection of low-level signals (e.g., low frequency signals) that overcome one or more of the limitations of conventional approaches are desired.

SUMMARY

The present disclosure is directed to an apparatus and method for sensing signals, and has particular application for sensing underwater acoustic and vibration signals.

In one embodiment, the present disclosure relates to a transducer including a cantilever coupled to a base. The cantilever may include a beam and a first coupling surface angularly oriented from the beam, and the base may include a second coupling surface angularly oriented from the beam and substantially parallel to the first coupling surface of the cantilever. The transducer may further include a sensing material coupled between the first coupling surface of the cantilever and the second coupling surface of the base.

In some embodiments, the first coupling surface of the cantilever may be obtusely oriented from the beam. In other embodiments, the first coupling surface of the cantilever may be acutely oriented from the beam. In another embodiment, the sensing material may include first and second surfaces and the sensing material may be configured to operate in a shear mode.

In a further embodiment, the surface of the sensing material may be in contact with the first coupling surface of the cantilever and the second surface of the sensing material may be in contact with the second coupling surface of the base. In another embodiment, the sensing material may have a rectangular cross-section. In one embodiment, the transducer may include a tine that couples the cantilever to the base. In a further embodiment, the tine may be configured to reduce the cross-axis sensitivity of the transducer and to enhance shear stress applied to the sensing material. In some embodiments, the cantilever may define the tine and the tine may extend into a void in the base. In another embodiment, the base may define the tine and the tine may extend into a void in the cantilever.

In another embodiment, the transducer may further include a proof mass. In some embodiments, the proof mass may be a distinct form, but coupled to the beam. In other embodiments, the proof mass may be integral with the beam. In a further embodiment, the sensing material may include a piezoelectric element. However, in other embodiments, the sensing material may include a piezoresistive element, or a different type of shear mode sensing material.

In some embodiments, the cantilever, the base and the sensing material may together form a first accelerometer, and the transducer may further include a second accelerometer and a third accelerometer, with the first, second, and third accelerometers mounted in a housing and together forming a vector sensor.

Another embodiment of the present disclosure may relate to a sensor including a cantilever coupled to a base. The cantilever may include a beam, and a sensing material may be embedded within the beam of the cantilever. The sensing material may include first and second surfaces that are angularly oriented from the beam.

In further embodiments, the sensing material may include a first piezoelectric element and a second piezoelectric element embedded within the beam. The second piezoelectric element may include third and fourth surfaces angularly oriented from the beam. In another embodiment, the third and fourth piezoelectric elements may be embedded within the beam. The third piezoelectric element may be oriented parallel to the first piezoelectric element and the fourth piezoelectric element oriented parallel to the second piezoelectric element. In another embodiment, the sensing material may include a piezoelectric shear mode element. In a further embodiment, the sensing material may have a parallelogram cross-section.

In a further embodiment, the cantilever may be coupled to the base at a first end of the cantilever and may include a proof mass coupled to a second end of the cantilever. Additionally, the cantilever may be coupled to the base at a first end of the cantilever and the sensing material may be embedded in the cantilever near the first end of the cantilever. In another embodiment, the beam may define a groove having a first inner wall, a second inner wall, and a third inner wall, where the third inner wall is substantially parallel to the first inner wall, and the sensing material is embedded within the groove. In another embodiment, the sensing material may be bonding the first and third inner walls, but not the second inner wall.

Another embodiment of the present disclosure may relate to a method. The method may include the acts of acquiring data from a transducer coupled to a body. The transducer may include a cantilever coupled to a base and including a beam defining at least one coupling surface. The transducer may further include at least one sensing element coupled to the at least one coupling surface. The sensing element may be a shear mode piezoelectric element. Some embodiments of the method may further include processing the data from the transducer to determine acoustic acceleration of the body in at least one directional component.

Another embodiment of the present disclosure may relate to another method. The method may include the acts of acquiring data from a transducer coupled to a body. The transducer may include a cantilever coupled to a base and including a beam defining at least one coupling surface that is angularly oriented with respect to a longitudinal axis of the beam. The vector sensor may further include at least one sensing element coupled to the at least one coupling surface. The sensing element may be subjected to shear stress as the beam is deflected relative to the base. In some embodiments, the method may further include the act of processing the data from the transducer to determine acoustic acceleration of the body in at least one directional component.

DETAILED DESCRIPTION

Scientists and engineers conduct “surveys” utilizing, among other things, seismic and other wave exploration techniques to find oil and gas reservoirs within the Earth. These seismic exploration techniques often include controlling the emission of seismic energy into the Earth with a seismic source of energy (e.g., dynamite, air guns, vibrators, etc.), and monitoring the Earth's response to the seismic source with one or more receivers. By observing the reflected seismic signals detected by the receiver during the survey, the geophysical data pertaining to reflected signals may be acquired and these signals may be used to form an image indicating the composition of the Earth near the survey location.

FIG. 1shows a side view of a vessel101towing a source102and several receivers103on streamers behind the vessel101. As is shown, the receivers103may be positioned just beneath the surface of the water. For the sake of discussion, the embodiment depicted inFIG. 1illustrates the source and receiver being towed by the same vessel, however other combinations are possible. For example, in other embodiments, either the source and/or receivers may be towed by separate vessels or may be implemented in land-based acquisition systems. In still other embodiments, the source and/or receivers may be stationary while the other is towed behind the vessel. In yet other embodiments, the receivers103may be positioned deeper in the water, for example, by using streamer steering devices, such as the DigiBIRD® and DigiFIN® brand steering devices available from ION Geophysical Corporation. In other embodiments, multiple sources may be used. Also, any type of source(s) or receiver(s) may be used, including for example, 1-, 2-, or 3-dimensional sources or receivers.

During operation, the source102may emit seismic energy (e.g., by an air gun), which may reflect off various portions of the Earth104and may be received back at the receivers103(as shown by the propagating seismic waves inFIG. 1). As will further be described below, each receiver103may include one or more transducers (not specifically shown inFIG. 1) used as accelerometers to measure the magnitude and direction of the reflected seismic energy. The receivers may further include other sensors and/or transmitting devices, such as a pressure sensor or a microphone. The signal received and processed at the receivers103may provide data that is useful in determining the composition of various portions of the Earth104proximate the location where the signal was reflected, which may include an oil and/or gas reservoir105. If the amount of oil and/or gas in the reservoir105is depleted over time, then subsequent surveys conducted in substantially the same location as the first survey may indicate various properties of this depletion such as: decreasing pore pressures, migration of oil/water and/or gas/water contacts, drop in acoustic impedance, and so forth.

FIG. 2illustrates one embodiment of a transducer200that may be used as a single-axis accelerometer (and which may be combined with other transducers200to form a tri-axial accelerometer or vector sensor in some embodiments). As is shown, the transducer200may include a cantilever202comprising a beam204defining a forward end206that is joined to a base structure201and a rear end208that is joined to a proof mass210. In one embodiment, the forward end206of beam204may be anchored to the base structure201via a tongue218or a tine that is joined to the base structure201. The tine or tongue218may serve to couple the beam204to the base structure201, and may further serve to reduce the cross-axis sensitivity of the transducer200and/or improve output signals in sensing elements222. The tine218may reduce the cross-axis sensitivity of the transducer200and/or improve output signals because the tine218may increase the bending stiffness of the cross-axis and provide a pivot point for the beam204during bending.

In one embodiment, the tongue218may be a strip of material that extends forwardly from the forward end206of the beam204into a receiving void or slot212defined by the base structure201. In one embodiment, the forward end of the tongue218may be joined to the base structure201using an adhesive, such as an epoxy adhesive. In other embodiments, the tongue218may be otherwise joined to the base structure201. For example, the tongue218may be keyed, and the base structure201may define a corresponding groove, such that mating the tongue218with the groove defined by the base structure201secures the tongue218to the base201. In further embodiments, the base structure201and the beam204may be formed from a single piece of material. Alternatively, the tongue218may be integral to the base structure201, and may extend into a slot or void in the cantilever202.

In some embodiments, the beam204may be formed from a flexible material that allows the beam204to bend slightly as the proof mass210is displaced by external forces (e.g., from seismic energy, vibrations, and so on) relative to the base structure201. The tongue218may be formed from the same material as the beam204(i.e., such that the beam204and the tongue218are formed from a single piece of material), or may be formed from a different material. In some embodiments, the tongue218may also bend slightly as the proof mass210is displaced by the external forces. As shown inFIG. 2, the tongue218may have a smaller thickness than the beam204, or may have the same thickness as the beam204. In some embodiments, the tongue may have sufficient thickness to support the weight of the proof mass201such that the beam204does not bend under the weight of the cantilever202alone (i.e., when no external forces are impacting upon the mass210).

As is shown, the forward end206of the beam204may define two coupling surfaces220that are positioned on opposite sides of the beam204. The coupling surfaces220may each be configured to receive one or more sensing elements222formed from a sensing material, such that at least a portion of the coupling surfaces220may contact at least a portion of one of the faces of the sensing elements222. In one embodiment, the sensing elements222may be formed from a piezoelectric material, such as piezoelectric crystal. In other embodiments, the sensing elements222may be formed from another type of shear mode sensing material, such as piezoresistive material, piezoceramic material, piezo-composite material, piezoelectric crystals, and so forth.

The base structure201may also define two coupling surfaces221that are each configured to receive one or more sensing elements222, such that at least a portion of the coupling surfaces221may contact at least a portion of one of the faces of the sensing elements222. In some embodiments, the coupling surfaces221of the base structure201may contact the bottom faces of the sensing elements222, and the coupling surfaces220of the beam204may contact the top faces of the sensing elements222, or vice versa. The coupling surfaces221,220, may be bonded to the faces of the sensing elements222at the contact points between the coupling surfaces211,220and the faces of the elements222, such as by an adhesive. In some embodiments, the coupling surfaces221of the base structure201may be substantially parallel to the coupling surfaces220of the beam, as shown inFIG. 2. However, in other embodiments, the coupling surfaces of the base structure201may be non-parallel to the coupling surfaces220of the beam204.

The coupling surfaces220,221may each define angles A, B relative to the longitudinal axis224of the beam204. In one embodiment, each coupling surface220,221may define an acute angle with respect to the longitudinal axis224of the beam204(e.g., between 0 and 90 degrees). In one embodiment, the angles A, B defined between the coupling surfaces220,221and the longitudinal axis224of the beam204may be substantially equal. However, in other embodiments, the coupling surfaces220,221may define different angles relative to the longitudinal axis of the beam204. For example, one of the coupling surfaces220,221may define an angle A that is 45 degrees with respect to the longitudinal axis224of the beam204, while the other of the coupling surfaces220,221may define an angle B that is 65 degrees with respect to the longitudinal axis224of the beam204. As is shown, the sensing elements222may each extend in a direction that is substantially non-perpendicular and non-parallel to the longitudinal axis of the beam204, but which is substantially parallel to the coupling surfaces220,221.

In one embodiment, the sensing elements222may define a rectangular shape having six opposing faces. In some cases, rectangular-shaped sensing elements may be easier and less expensive to manufacture than some other configurations of sensing elements, which may result in a cost savings in manufacturing the transducer200. In other embodiments, however, the sensing elements may be another configuration. For example, the sensing elements may define some other polyhedron shape, or may define one or more rounded edges. In one particular embodiment, the sensing elements may define a parallelepiped, in which the top and bottom faces of the sensing elements may be parallel to one another, and the end faces of the sensing elements may be parallel to one another. In such embodiments, the sensing elements may each have a parallelogram-shaped cross-section. In another embodiment, the sensing elements may define a prism shape.

As forces (represented by arrows226and228) normal to the longitudinal axis of the beam are applied to the proof mass210, the mass210may be displaced relative to the base structure201. The beam204carries the load to the forward end206, where the forces226,228are converted to shear stress (represented by arrows230) that is resisted by the sensing elements222. In the embodiment shown inFIG. 2, the shear stress230may arise from force vector components that are substantially parallel to the coupling surfaces220,221of the beam204and the base201. As shear stress230is applied to the sensing elements222, the piezoelectric material forming the sensing elements222may be loaded according to Newtonian mechanics, resulting in a change in electric charge or voltage that can be detected and measured.

In one embodiment, the sensing elements222may be formed from shear mode piezoelectric material. Shear mode piezoelectric material may be highly sensitive, and may have a larger charge coefficient than some other piezoelectric sensing modes. In some embodiments, the shear mode piezoelectric material may be configured to generate an electric charge that is proportional to the amplitude of the stress forces impacting upon the sensing elements222. For example, one embodiment may utilize PMN-PT piezoelectric crystal, which has a d15 charge coefficient (approximately 5000 pC/Newton). Another embodiment may utilize piezoresistive material, rather than piezoelectric material. A piezoresistive material may convert shear stress into a change in resistance that is proportional to the shear stress amplitude of the applied force. In such embodiments, an electric conditioner configured to detect this charge or resistance change may be coupled to the sensing elements and may generate a measurable voltage in the range of tens of micro-volts to hundreds of micro-volts. Piezoresistive materials may also have a relatively high shear mode piezoresistance coefficient. For example, a doped Silicon crystal may have a shear mode piezoresistance coefficient π44at 138×10−11/Pa.

Utilizing shear mode piezoelectric elements in connection with the disclosed transducer200provides many benefits. For example, the cantilever structure of the transducer200may be well-suited for detecting vibrations at low-frequencies, while the shear sensing structure may be well-suited for detecting vibrations at high-frequencies. The disclosed transducer200combines the advantages of the shear mode material with the cantilever beam design, and is therefore highly efficient in detecting acoustic or vibration signals in a frequency range suitable for seismic imaging, among other applications. Additionally, the flex shear piezoelectric transducers described herein may have a smaller size than other types of piezoelectric elements, which allows the resulting transducer200to be lighter and more compact in design than other types of transducers, while maintaining high sensitivity to a range of vibrations.

FIG. 3illustrates a schematic diagram of some of the electrical connections that can be used in connection with the embodiment of the transducer200shown inFIG. 2. As is shown, each sensing element222may be electrically coupled to the cantilever beam204and to the base201, and the sensing elements222may be oriented such that they are of opposing polarity to one another. In some embodiments, the beam204and the base structure201may each be electrically coupled to a voltage measurement device (not specifically shown) that is configured to measure the voltage provided by the transducer200as the proof mass210is deflected. In one embodiment, the beam204and the base structure201may be coupled to the voltage measurement device via one or more output wires250.

As the proof mass210is displaced, the sensing elements222may be subjected to shear stress, producing a differential charge in the sensing elements222that is proportional to the stress applied. The charge produced may cause a potential difference between the beam204and the base structure201, which can be measured by either a voltage or a charge measurement device. The potential difference may change polarity depending on the direction in which the proof mass210is displaced. For example, deflection of the proof mass210in one direction may cause a positive potential difference, while deflection of the proof mass210in the other direction may cause a negative potential difference.

In the embodiment illustrated inFIG. 3, the beam204and the base structure201may be formed from an electrically conductive material, such that the charge generated by the sensing elements222may flow through the beam204. For example, the beam may be formed from steel, aluminum, or an alloy formed from multiple types of metal. In embodiments where the beam is formed from a conductive material, the tine218may be coated with a non-conductive material in order to prevent a short from the beam204to base201. In other embodiments, the beam204and the base structure201may be formed from a non-conductive or substantially non-conductive material, such as alumina, ceramic, or plastic. In such embodiments, the output wires250may be directly coupled to the sensing elements222, rather than to the beam204or the base structure201. Alternatively, the base structure201and/or beam204may be plated with an electrically conductive material to provide electric access to the sensing element222.

FIG. 4illustrates another embodiment of a transducer300. Similar to the embodiment shown inFIG. 2, this embodiment may include a cantilever including a beam304coupled to a proof mass310. The beam304may also define a tongue318that anchors the beam304to a base structure301. In this embodiment, the beam304may define a y-shape, where the rear end308of the beam304may have a linear structure, while the forward end306of the beam304may define two arms305that extend at angles away from one another. The inner surfaces of the arms305may each define a coupling surface320that is configured to contact one or more sensing elements322. As is shown, each of the coupling surfaces320may define an obtuse angle C, D that is between 90 and 180 degrees relative to the longitudinal axis324of the beam304.

As is shown, the base structure301may have a protruded portion307that defines two angled coupling surfaces321configured to contact the sensing elements320. Similar to the embodiment shown inFIG. 2, the coupling surfaces321may be substantially parallel to the coupling surfaces320defined by the beam304. In some embodiments, the coupling surfaces321of base structure301may define an angle C, D relative to the longitudinal axis324of the beam304that is substantially equal to the angle C, D defined by the corresponding coupling surfaces of the beam304. In other embodiments, the coupling surfaces321of the base structure301may be non-parallel to the coupling surfaces320of the beam304.

Similar to the embodiment shown inFIG. 2, the transducer300shown inFIG. 4may provide a measurable voltage in response to normal forces impacting on the proof mass310. This voltage may vary from several mV to hundreds of mV when a piezoelectric material is used for the sensing elements322, for example, and may depend on the input signal level. As described above with respect toFIG. 2, the tongue318and/or the length of the beam304may be formed from a flexible material that allows for deflection of the proof mass310in response to the normal forces that are applied to the mass310. As the proof mass310is deflected, the sensing elements322are subjected to shear stress (represented by arrows330), and produce a voltage that can be measured by a voltage measuring device (not specifically shown).

In contrast to the embodiment shown inFIG. 2, in which the sensing elements222are oriented in a forwardly-slanted direction, the sensing elements322of the transducer300shown inFIG. 4are oriented in a rearwardly-slanted direction. The embodiment shown inFIG. 4nonetheless allows for the generation of shear forces across the sensing elements322as the proof mass310is displaced due to the angled coupling surfaces320,321to which the sensing elements322are mounted.

While the examples of beams204,304illustrated inFIGS. 2 & 4are of substantially uniform thickness along their length, other embodiments may utilize beams204,304that have varying thickness along their length. As an example, the rear end208,308of the beam204,304may be thinner or thicker than the forward end208,308of the beam204,304. Alternatively, the beam204,304may be notched or include various protrusions along its length.

Additionally, other embodiments may not utilize a proof mass210,310that is joined to the beam204,304. In such embodiments, the proof mass210,310may be integral to the beam, rather than a distinct form coupled to the beam. For example, in some embodiments, the beam204,304may have a thicker rear end208,308that functions similar to the proof mass210,310described above with respect to the embodiments shown inFIGS. 2 and 4. In further embodiments, the beam204,304, may have a substantially uniform thickness along its length.

Other embodiments may also utilize other configurations of proof masses210,310. WhileFIGS. 2-4illustrate a rectangular-shaped proof mass210,310, other embodiments may utilize proof masses having other configurations. For example, a circular proof mass or a pyramid-shaped mass may be used.

FIG. 5illustrates another embodiment of a transducer400. While the embodiments shown inFIGS. 2 and 4illustrate transducers200,300in which a single sensing element222,322is positioned on each side of the beam204,304, this embodiment includes multiple sensing elements422positioned on opposite sides of the beam404. For example, one or both sides of the beam404may include two or more sensing elements422positioned between the beam404and the base structure401. The charge output by each sensing element422may be transmitted to a voltage measurement device (not specifically shown), thereby increasing the sensitivity of the transducer400. In other embodiments, different numbers of sensing elements422may be positioned on opposite sides of the beam404, making the transducer more sensitive to deflection of the proof mass410in one direction than the other.

FIG. 6illustrates another embodiment of a transducer500. This embodiment is similar to the embodiment depicted inFIG. 2, described above. However, in this embodiment, the beam504may define one or more notched or stepped portions511adjacent the coupling surfaces520that help to align the sensing elements522with the beam504during manufacturing. In some embodiments, the base501may also or alternatively include corresponding notched or stepped portions that are configured to catch the ends of the sensing elements522to facilitate alignment of the sensing elements522with the base501during manufacturing.

FIG. 7illustrates another embodiment of a transducer600, with the base structure removed. In this embodiment, the forward end606of the beam may include four arms605. The arms may be similar in structure as the arms305of the beam304shown inFIG. 4, wherein each of the arms605define an angled coupling surface620relative to the longitudinal axis624of the beam604. Similar to other embodiments, the coupling surfaces620may each be configured to receive one or more sensing elements622. This particular embodiment includes two pairs of sensing elements622(for a total of four sensing elements622), with each pair of sensing elements622including two sensing elements mounted on opposite sides of the beam from one another. As is shown, the first pair of sensing elements622may be positioned along a first axis (represented by dotted line660), and the second pair of sensing elements622may be positioned along a second axis (represented by dotted line661) that is substantially perpendicular to the first axis660.

In this embodiment, the transducer600may be used as a dual axis accelerometer because it can sense acceleration applied along each of the first and second axes660,661. For example, when the proof mass610is deflected in a direction along the first axis660, the sensing elements622positioned along the first axis660may be subjected to shear stress, resulting in the generation of a measurable voltage across these sensing elements622. When the proof mass610is deflected in a direction along the second axis661, the sensing elements622positioned along the second axis661are subjected to shear stress, resulting in the generation of a measurable voltage across these sensing elements622. Accordingly, the transducer600shown inFIG. 7may be used in measuring external forces applied in multiple directions and across multiple dimensions. The charge generated on the surface(s) of each one or each pair of sensing elements622may be separated (e.g., decoupled) in some embodiments, and further may be provided to a voltage measurement device.

Other embodiments may include more or fewer sensing elements622that are positioned along other axes of the beam. For example, other embodiments may include three sensing elements622that are positioned along axes that are each 120 degrees apart from one another, rather than perpendicular to one another. As another example, some embodiments may include eight sensing elements622that are positioned along axes that are 45 degrees apart from one another. The charge generated on the surface(s) of each one or each pair (or other combination) of sensing elements622may be separated (e.g., decoupled) in some embodiments, and further may be provided to a voltage measurement device.

FIG. 8illustrates another embodiment of a transducer700, in which the sensing elements722are embedded into the beam704. In this embodiment, the beam704may define multiple slots770or grooves configured to receive one or more sensing elements722. The slots770may include two opposing coupling surfaces720that are configured to engage the side faces of a sensing element722, as well as an end wall723configured to engage the end wall of the sensing element722. In some embodiments, the two opposing coupling surfaces720may be bonded to a sensing element received within the slot, but the end walls723of the slots770may remain unbonded to the corresponding end wall of the sensing element722. In other embodiments, each of the faces of the sensing element722may be bonded to the walls723,720of the slots. As is shown, the opposing coupling surfaces720may be substantially parallel to one another, and the end wall723may be substantially parallel to wall of the beam704. In other embodiments, the opposing coupling surfaces720may be non-parallel to one another. The charge generated on the surface(s) of each one or each pair (or other combination) of sensing elements722may be separated (e.g., decoupled) in some embodiments, and further may be provided to a voltage measurement device.

Similar to other embodiments, the coupling surfaces720may extend at angles E, F relative to the longitudinal axis724of the beam704. For example, in one embodiment the coupling surfaces720may define an angle E, F relative to the longitudinal axis of the beam that is between 0 and 90 degrees (i.e. an acute angle). In such embodiments, the sensing elements722may be positioned in a forward-slanting orientation. In another embodiment, the coupling surfaces may define an angle that is between 90 and 180 degrees (i.e. an obtuse angle) relative to the longitudinal axis of the beam, such that the sensing elements722may be positioned in a rear-slanting orientation.

In the embodiment shown inFIG. 8, the slots770may be located at the same position along the length of the beam704. However, in other embodiments, a first slot770may be located at one position along the length of the beam704, while the other slot770(located on the opposite side of the beam704from the first slot770) may be located at another position along the length of the beam704(e.g., further or closer to the front or rear ends706,708of the beam704).

FIG. 9illustrates another embodiment of a transducer800. This embodiment is very similar to that shown inFIG. 8, but the beam804in this embodiment may include multiple pairs of slots870or cutouts (as shown inFIG. 8) along the length of the beam804that are each configured to receive one or more sensing elements822. As is shown, the sensing elements822located on one side of the beam804may be substantially parallel to one another, and the sensing elements822located on the other side of the beam804may also be substantially parallel to one another. In other embodiments, however, the sensing elements822may be oriented such that they are non-parallel to one another.

In some embodiments, each one or each pair of sensing elements822may be coupled to a voltage measurement device (not specifically shown) in order to capture and/or measure the charge generated on one or more surfaces of the sensing elements822. As proof mass810is displaced, the beam804may be deflected along its length, and each pair of sensing elements822may be subjected to different levels of shear stress, based on their position along the length of the beam804. Accordingly, this transducer800may allow for increased sensitivity since multiple voltage readings may be obtained along the length of the beam804each time the proof mass810is displaced. In some embodiments, sensing elements822may be positioned on four sides of the beam804in order to have a dual axis response, similar to that described above with reference toFIG. 7.

FIG. 10illustrates one embodiment of a packaged seismic receiver900that includes multiple transducers902,904,906that together can be used as a tri-axial accelerometer. The transducers902,904,906may be similar to those previously described with respect to prior embodiments. As is shown, each of the transducers902,904,906may be mounted to an enclosed housing908that contains all of the transducers902,904,906. Additionally, the receiver900may further include other components, such as a hydrophone910or other sensing device configured to measure acoustic pressure, as well as an electronic conditioner912, such as a voltage measurement device or an amplifier that is coupled to transducers902,904,906. In some embodiments, the housing908may be fully or partially covered by a foam material914or other low-density material that does not add significant weight to the receiver900. In one embodiment, the foam material914may be syntactic foam.

As is shown, the transducers902,904,906may each be configured to sense acoustic particle acceleration applied in different directions903,905,907. For example, the transducers902,904,906may be oriented such that they are substantially orthogonal to one another. In one embodiment, the transducers902,904,906may be oriented substantially orthogonally to one another, such that the transducers902,904,906may sense acoustic particle acceleration in the X, Y, and Z directions903,905,907, as shown inFIG. 10. In other embodiments, the transducers902,904,906may be oriented at other angles relative to one another.

In some embodiments, the receiver900may include a relatively large amount of void space within the housing to affect its buoyancy. For example, in one particular embodiment, the equivalent density of the receiver900may be less than or equal to approximately five (5) times the density of water so that the receiver900can follow the acoustic particle velocity. The buoyancy of the receiver900may be further increased by the foam914surrounding the housing908. Additionally, as shown, the receiver900may have a length L1 that is less than or equal to approximately half of the wavelength L2 of the upper bound frequency of an acoustic wave.

During operation, the receiver900may be displaced by acoustic waves moving through the water, such that the receiver900follows the movement of the acoustic waves. The transducers902,904,906may each be configured to sense the amount of acoustic acceleration (i.e., velocity) of the receiver900as it moves in the water in one directional component903,905, or907(e.g., X, Y, or Z). Other embodiments may include more or fewer transducers such that the receiver900may be capable of sensing acoustic acceleration in more or fewer directions.

FIG. 11illustrates an embodiment of a computer system735capable of processing the data from one or more transducers or receivers to determine the acoustic acceleration of a body in at least one directional component. The transducer(s) may be similar to any of the embodiments described above and shown inFIGS. 2-9. In some embodiments, the computer system735may be a personal computer and/or a handheld electronic device aboard the vessel101(shown inFIG. 1). In other embodiments, the computer system735may be an implementation of enterprise level computers, such as one or more blade-type servers within an enterprise in a land-based computer system. A keyboard740and mouse741may be coupled to the computer system735via a system bus748. The keyboard740and the mouse741, in one example, may introduce user input to the computer system735and communicate that user input to a processor743. Other suitable input devices may be used in addition to, or in place of, the mouse741and the keyboard740. An input/output unit749(I/O) coupled to the system bus748represents such I/O elements as a printer, audio/video (A/V) I/O, etc.

Computer735also may include a video memory744, a main memory745and a mass storage742, all coupled to the system bus748along with the keyboard740, the mouse741and the processor743. The mass storage742may include both fixed and removable media, such as magnetic, optical or magnetic optical storage systems and any other available mass storage technology. The bus748may contain, for example, address lines for addressing the video memory744or the main memory745.

The system bus748also may include a data bus for transferring data between and among the components, such as the processor743, the main memory745, the video memory744and the mass storage742. The video memory744may be a dual-ported video random access memory. One port of the video memory744, in one example, is coupled to a video amplifier746, which is used to drive a monitor747. The monitor747may be any type of monitor suitable for displaying graphic images, such as a cathode ray tube monitor (CRT), flat panel, or liquid crystal display (LCD) monitor or any other suitable data presentation device.

The computer system includes a processor743, which may be any suitable microprocessor or microcomputer. The computer system735also may include a communication interface750coupled to the bus748. The communication interface750provides a two-way data communication coupling via a network link. For example, the communication interface750may be a satellite link, a local area network (LAN) card, a cable modem, and/or wireless interface. In any such implementation, the communication interface750sends and receives electrical, electromagnetic or optical signals that carry digital data streams representing various types of information.

Code received by the computer system735may be executed by the processor743as the code is received, and/or stored in the mass storage742, or other non-volatile storage for later execution. In this manner, the computer system735may obtain program code in a variety of forms. Program code may be embodied in any form of computer program product such as a medium configured to store or transport computer readable code or data, or in which computer readable code or data may be embedded. Examples of computer program products include CD-ROM discs, ROM cards, floppy disks, magnetic tapes, computer hard drives, servers on a network, and solid state memory devices. Regardless of the actual implementation of the computer system735, the data processing system may execute operations that allow for the filtering using repeatability and other metrics.

While the embodiments described above are primarily described in connection with detecting seismic energy, a person of skill in the art will appreciate that these embodiments may also be used for other purposes. For example, the disclosed transducers may be used to measure vehicle acceleration, vibration on cars, machines, buildings, process control systems, safety installations, and so on. Additionally, the disclosed transducers may be used in smartphones, digital audio players, and other electronic devices utilizing transducers to determine the orientation of the device relative to the user. A person of skill in the art will further appreciate that the disclosed transducers may have a multitude of applications associated with other types of transducers, including, but not limited to, applications in engineering, biology, industry, medicine, transportation, navigation, and gravimetry. Furthermore, a person of skill in the art will appreciate that as described above, the transducers described herein may be used as sensors, but they may also or alternatively be used as actuators where a voltage is applied to the piezoelectric sensing material and the beam moves as a result of the applied voltage.

The apparatuses and associated methods in accordance with the present disclosure have been described with reference to particular embodiments thereof in order to illustrate the principles of operation. The above description is thus by way of illustration and not by way of limitation. Various modifications and alterations to the described embodiments will be apparent to those skilled in the art in view of the teachings herein. Those skilled in the art may, for example, be able to devise numerous systems, arrangements and methods which, although not explicitly shown or described herein, embody the principles described and are thus within the spirit and scope of this disclosure.

Accordingly, it is intended that all such alterations, variations, and modifications of the disclosed embodiments are within the scope of this disclosure as defined by the appended claims.

In methodologies directly or indirectly set forth herein, various steps and operations are described in one possible order of operation, but those skilled in the art will recognize that the steps and operations may be rearranged, replaced, or eliminated without necessarily departing from the spirit and scope of the disclosed embodiments.

All relative and directional references (including: upper, lower, upward, downward, upgoing, downgoing, left, right, top, bottom, side, above, below, front, middle, back, vertical, horizontal, middle, and so forth) are given by way of example to aid the reader's understanding of the particular embodiments described herein. They should not be read to be requirements or limitations, particularly as to the position, orientation, or use of the invention. Connection references (e.g., attached, coupled, connected, joined, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, connection references do not necessarily infer that two elements are directly connected and in fixed relation to each other, unless specifically set forth in the claims.