Abstract: An improvement for the drive control system of a vibratory sound source used in seismic exploration comprising apparatus for generating a feedback signal proportional to the instantaneous acceleration of the reaction mass structure of the sound source's hydraulic drive system. Degenerative feedback of the signal so developed is used to reduce distortion of the vibratory seismic signal imparted into the earth.

Abstract: An apparatus for introducing vibrations into the ground including a container having electrodes mounted therein with electrical connections leading from a source of electric potential to said electrodes, salt water substantially filling the container, and means for placing the container on the ground in position to transmit vibrations to the ground.

Abstract: The invention relates to a nondestructive downhole seismic source capable of generating S.sub.V -waves, S.sub.H -waves, and P-waves alone or in combination to determine information about a surrounding geologic formation. The invention also includes processes of performing crosswell tomography and reverse vertical seismic profiling. The invention also includes a means and process to carry out in hole seismic logging operations.

Abstract: A device for generating pulsed radial stresses to the wall of a well by application of pulses to anchorage shoes of a body lowered in the well, at the end of a cable provided with electric power supply and signal transmission lines. The device comprises hydraulic jacks for controlling the anchorage shoes, a main hydraulic system comprising an accumulator for placing the anchorage shoes in contact with the wall of the well and an auxiliary hydraulic system comprising an accumulator for applying short pulsed radial stresses to the anchorage shoes in the anchorage position. The hydraulic systems are electrically supplied through the cable.

Abstract: The present invention is an improvement to conventional baseplates for imparting seismic energy to an earth formation. A baseplate typically has a plurality of downwardly disposed triangular prism-shaped cleats for engagement with the earth surface above an earth formation under seismological investigation. At least one leaf spring is supported about midway along its length from the lower surface of the baseplate and between the cleats. An elongate horizontal ejector member is slidably interconnected to the respective ends of the spring. In operation, as the baseplate is lowered into engagement with the earth surface the ejector member is moved upward and the leaf spring is compressed. When the baseplate is lifted upward the restoring force of the leaf spring results in a generally downward force against the ejector member.

Abstract: A transportable seismic energy source having a baseplate for contacting the earth, an upper master cylinder affixed at its lower end to the base plate and extending uprightly from it, a receiving cylinder of outside diameter less than the internal diameter of the master cylinder and supported coaxially within the upper portion of the master cylinder, the master cylinder and receiving cylinder being filled with liquid, a slug firing gun mounted to the master cylinder and arranged so that the gun muzzle extends coaxially and above the receiving cylinder.

Abstract: The present invention provides a method and apparatus for controlling the response of a seismic vibrator during its actuation period. The sweep input signal is modified in response to an average of the force applied to the earth by the vibrator over at least one cycle of the sweep signal. Additionally, this modified drive signal may be further adjusted by selective adjustment of the amplitude of the signal within selected frequency ranges.

Abstract: Multiple vehicle-transported impact-type surface seismic sources designed to shoot along slant paths to create combined compressional and shear wave pulses in the earth are provided with radio controlled actuators. The azimuth of each shooting path is automatically referenced to magnetic north so that signals of equivalent wave form contents are produced despite vehicle misalignments and without reliance upon individual vehicle operators.

Abstract: A baseplate for a seismic vibrator is formed from two identical cast plate members having stiffening ribs and alternating plug and socket cones along the ribs. The cast plate members are arranged together to align opposed plug and socket cones of the plates and are connected by attaching mechanisms passing through holes in the aligned cones. The aligned cones accomplish a wedging or clamping action on each other when the plate members are connected.

Abstract: Method and apparatus for downhole seismic exploration employing vibration emanating from a point deep in a well. An elastic steel column has an upper end extending above the top of the well. A reaction mass is attached vertically thereabove through a vertically mounted compression spring system, in parallel with it a vertically mounted servo-controlled hydraulic cylinder-piston assembly. The displacement of a spear or bit on the lower end of the column relative to earth develops a displacement signal. The piston in the hydraulic cylinder is under reciprocated servo control to apply vertical vibration to the upper end of the column and thereby to the spear, while developing an electrical, pressure-differential signal corresponding to the pressure across the cylinder-piston assembly.

Abstract: A method and apparatus for generating a seismic wave in a borehole in the earth is disclosed. A portion of the borehole, which may be the bottom of the hole or any other point along its length, is selected as the site for seismic wave generation. A device is provided to oscillate the borehole fluid in a selected portion of the borehole to establish a resonant standing pressure wave of desired frequency within the fluid. The wave is maintained by continuing to supply energy to the fluid to replace losses due to fluid friction, structural losses and radiated acoustic energy. The standing wave thus created is radiated through the borehole wall into the earth and is eventually received by seismic detectors located on the surface.

Abstract: A seismic acoustic source for generating acoustic pulses in both solid rock and sedimentary layers on land and in both water, rock and sedimentary layers at sea comprises: two chambers; a high pressure chamber and a low pressure chamber communicating but separated from each other by, for example, a first diaphragm, the low pressure chamber being closed by, for example, a second diaphragm. The high pressure chamber contains gas e.g. helium at high pressure whereas low pressure chamber contains a gas such as carbon dioxide at a lower pressure. The pulse is generated by bursting the diaphragm separating the two chambers whereupon the shock wave generated in the carbon dioxide then travels to the other end of the low pressure chamber and leaves by over-pressure behind the shock bursting the second diaphragm. Repetitive operation may be achieved by replacing the first diaphragm with a shock wave valve and the second with operable valve means such as an iris diaphragm or full-bore gate valve.

Abstract: A vibrator baseplate for use in a seismic signal transducer system has a bottom plate with a dome centrally located thereon. A pair of partial domes overlap the central dome on opposite sides thereof. Top plates are attached to the partial domes, which are also attached to the bottom plate. Internal rib stiffeners are provided within each dome and gusset members extend between the partial domes and the top plates. Means are provided to connect the baseplate to the seismic signal transducer system. Alternatively, the baseplate comprises a bottom plate with an elongate eccentric dome attached thereto.

Abstract: Apparatus for measuring the force actually exerted by the base plate of a seismic vibrator on the earth surface is provided. This apparatus consists of a plurality of individual sensor elements, which are arranged on the side of the base plate which is directed towards the earth surface. The sensor elements couple the energy from the base plate to the earth surface.

Abstract: A vibratory seismic surface source includes a single vibrating mass, the energy of which is coupled with the earth through a ground contacting base plate. The vibrating mass is connected to the base plate by means of a ball and socket joint which constitutes a universal pivot for the vibratory axis of the mass. Thus, this vibratory axis may be made to assume any vector path with respect to a seismic line. In this manner, any desired combination of compressional and shear waves, both SH and V type, may be generated and recorded simultaneously at a point on the earth's surface remote from the source.

Abstract: A full waveform seismic source is described which is adapted to propel a heavy mass powerfully downward against the surface of an earth-contacting target plate. Means are provided for rotating the barrel of the actuator about two mutually perpendicular horizontal axes so that energy can be delivered to the earth along a plurality of preselected slant paths. In this way, any desired combination of compressional and shear waves, both SH and SV type, may be generated at a point on the earth's surface. The target is contoured so that any slant path followed by the accelerating mass always impacts the target normal to its surface.

Abstract: A vibratory seismic surface source includes a single vibrating mass, supported above and independently of an earth-contacting base plate. Means are provided for varying the inclination and azimuth of the vibrator axis. After the vibrator is oriented in any desired direction, it is then lowered along its vibratory axis so that it bears directly against the hemispherically concave upper surface of the base plate. When the vibrator is actuated in this position of contact, any desired combination of compressional and shear waves, both SH and SV type, may be generated and recorded simultaneously at a point on the earth's surface remote from the source.

Abstract: An improved vibrator system for seismic geophysical prospecting, comprising a sealed chamber having two parts which reciprocate axially with respect to each other providing a sealed space between the two parts. One part connected to a baseplate, the other part connected to a reaction mass. Means for injecting into the sealed space a pulsating flow of high pressure fluid in response to which the two parts will vibrate with respect to each other. At least a single output opening comprising a valve, the cross-sectional area of which is a function of the displacement between the two parts of the vibrator.

Abstract: A vibratory seismic surface source includes a hydraulic vibrator the energy of which is coupled into the earth through a ground contacting base plate. The vibrator is supported above and independently of the base plate so that it may be pivoted about a first rotational axis within a truck-mounted gimbal-type frame which itself is tiltable about a second horizontal rotational axis perpendicular to the first. After the vibratory axis is oriented in the desired direction the vibrator is lowered so as to contact a suitably contoured upper surface of the base plate. Inclination of the vibrator is accomplished by "push-pull" operation of pairs of oppositely-directed hydraulic cylinders.

Abstract: An echo ranging gun (10) is disclosed which is useable with high pressure gas wells having gas pressure exceeding 15,000 psi. The gun (10) is connected to the needle valve (30) typically encountered on a well having high pressure. The needle valve can have a diameter as small as approximately 1/8 inch. The gun (10) has a passage (38) which is exposed to the gas in the wellbore (14) and a volume chamber (46). A poppet valve (56) is movable between open and closed positions in the volume chamber by rotating a wing handle (88) connected to a head (78) within the volume chamber (46) which has a ramp (80) to contact the poppet valve (56) to move the valve to the closed position. A bleed valve (112) is used to bleed the wellbore gas from the volume chamber to create a predetermined pressure differential between the passage (38) and volume chamber (46). Further rotation of the wing handle (88) causes the poppet valve (56) to be released from the ramp at a down step (86).

Abstract: A quantity of a solution of a long-chain polymer is injected into the water around an air gun. The resulting dilute solution of the long-chain polymer tends to reduce turbulence surrounding the air bubble that is created when the gun is fired.

Abstract: A method for generation of acoustic vibrations based on shock excitation of a magnetostriction transducer by a pulse electrical signal. The electrical signal is generated in the form of unidirectional half-cycles of cosinusoidal voltage, with a duration from one to two half-cycles of acoustic vibrations produced by the loaded tansducer. The repetition frequency of the electrical pulses is taken to be equal to, or multiple of the frequency of acoustic vibrations.A source of acoustic vibrations comprises a power unit (7), a pulse repetition frequency control unit (10) and a reservoir capacitor (6), the plates whereof are connected through a power circuit of a switching element (5) to a field winding (2) of the magnetostriction transducer (1). The source also comprises an auxiliary field winding (3) disposed on the same magnetostriction transducer (1) and connected by the aiding connection method to the winding (2); an auxiliary switching element (8); and a switching element control unit (9).

Abstract: An expendable sound source provides a cost effective projection of acoustic nergies in the ocean. A tubular housing contains a d.c. motor that locates its shaft coaxial with the housing. Cylindrically-shaped camming blocks engage spurs in a pair of rigid pistons at both ends of the tubular housing to reciprocate them in accordance with the pattern of the camming surfaces and the motor speed. A flywheel on the shafts and journaling supports assure the projection of arbitrary waveforms and a key-and-keyway cooperation between the housing and prevents the pistons turning in the housings. A self-contained, high energy battery pack is actuated by magnetic reed switch to assure reliable long term projection after deployment. Pressure compensation can be included.

Abstract: The claimed invention is directed to seismic exploration wherein an earth surface vibrator sweeps through a frequency range with varies with time as a function of frequency.

Abstract: The shear wave source of this invention includes a housing and means for applying forces to the shot hole wall. The force applying means applies a number of forces to the shot hole wall along lines normal to a plane close to the shot hole. No pressure waves, but only shear waves are generated at distant points on the plane. At least one of the forces is applied in opposite direction to the other forces to reduce the net recoil of the housing.A first, second and third force are applied at three source points in the observation plane along three lines normal to the plane to generate respectively a first, second and third shear wave in the plane. The first and third forces are equal in magnitude and the second force has twice the magnitude of the first force. The first and third forces are applied along lines in the same direction, but the second force is applied along a line opposite in direction to the lines of the first and third forces.

Abstract: Method and apparatus for the generation of low frequency acoustic energy such as may be employed in carrying out seismic surveys in marine environment. In imparting an acoustic energy pulse into a body of water, a planar electroacoustic transducer having parallel transducer plates is employed. The transducer plates have conforming electrical conductive paths. An impulse of opposed current flow is applied to the conductive paths to produce an electromagnetic field between the conforming paths which forces the transducer plates apart, generating an acoustic impulse having a center band frequency of less than 350 hertz. The wave length of the acoustic impulse at this frequency is less than twice the major planar axis of the transducer. The conductive paths may be formed of elongated conductors which are oblong in cross section and cover most of the radiating surface of the transducer.

Abstract: A gas gun assembly for measuring depths of reflectors in a well bore includes a housing having a central chamber and bottom bulkhead through which a first valve bore extends. Coupling structure is provided to connect the housing to the well. A cap closure for the chamber has a second valve bore therethrough of diameter larger than the diameter of the first valve bore and is located in axial alignment with the first valve bore. A valve stem has one end axially movable within the second valve bore while closing the same and the other end movable into and out of the first valve bore. A predetermined pressure condition is established across the bulkhead. The valve stem is then released for rapid equalization of pressure across the bulkhead to produce an acoustic pulse in the well bore.

Abstract: Methods and devices are disclosed for generating acoustic pulses in a water or land medium, e.g., for use in seismic investigations. The pulse amplitudes, waveshapes, and frequencies can be controlled by signals that may originate at a remote location. Compressed gas is confined at high pressure in a valve chamber (12, 194). An initiating signal causes the opening of a passage (54, 56, 192) from the chamber into the medium to initiate the rise of a pressure pulse therein. A second signal causes the closing of the passage in a manner such that the initial rise of the pressure pulse is limited by the closure of the passage. In one device, the passage is opened by one sleeve valve member (60) and closed by another sleeve valve member (58). In another device the passage is opened by a sleeve valve member (196) whose motion to open the passage is arrested substantially instantaneously by transferring its momentum to a momentum exchange sleeve (246) that is then gradually decelerated.

Abstract: Apparatus for determining the position of a gas-saturated porous rock in the vicinity of a deep borehole in the earth, drilled to a selected depth below the expected position of the porous rock. The apparatus includes a source of seismic waves of selected characteristic, positioned at a selected point in the borehole, with an array of geophones positioned on the earth in known positions around the borehole. These geophones are adapted to receive the seismic waves generated by the source in the borehole, after traveling upwardly through the earth, and to produce corresponding facsimile electrical signals. If the seismic waves from the source, in their upward movement to the surface, pass through a gas-saturated porous rock they will be attenuated, and therefore the signals from the geophones which are in the shadow of this gas-saturated rock will show a change of character and/or an attenuation.

Abstract: A high resolution seismic data acquisition system is made up of an electronically-fired shotgun source integrally connected to a detector-recording means displaced from the shotgun source.

Abstract: A method is described for causing hollow glass spheres to implode on command while deep in the ocean, whereby to produce an acoustic pulse. Specific means for causing the spheres to implode are described. The invention is useful for seismic work.

Abstract: A method of seismic surveying which provides a horizontal profile of reflector surfaces located between two spaced apart drillholes which profile appears similar to that of a marine type seismic reflection profile. The method comprising raising and lowering a seismic source and receiver in adjacent drillholes to provide a profile of reflectors which are located between the drillholes.

Abstract: The present invention relates to means for coupling the horizontally-directed force of a seismic transducer into the earth as a downward going shear wave. The coupling means consists of a plurality of downwardly convergent wedge-shaped earth-engaging cleats mounted on the transducer support means. The cleats differ from each other as to depth and sharpness, the sharper cleats being the deeper ones, so that they contact the earth's surface prior to the blunter ones and penetrate hard surfaces more readily. The blunter cleats, on the other hand, slow the rate of penetration in softer materials and thus prevent bottoming out. The cleats are configured so that the total edge length of the sharper cleats is less than that of the blunter ones, further insuring a high vertical loading on initial contact with hard surfaces. This construction permits efficient coupling into the earth of the horizontal force of a vibrator in soils and other earth materials varying widely in competency while minimizing bottoming out.

Abstract: The present invention relates to means for coupling the horizontally directed force of a seismic transducer into the earth with a downward-going shear wave. The coupling means consists of a plurality of downwardly-convergent, wedge-shaped, earth-engaging cleats dependently attached to the transducer support means, at least some of the cleats being provided with a plurality of downwardly projecting teeth, which may be mounted on or form a part of field replaceable cleat inserts. Extremely high unit pressures are developed on these teeth due to the hold down weight of the transducer. As a result, good earth penetration is achieved immediately on even very hard rock surfaces. The alignment of the teeth is such as to encourage the development of rock flaws or cracks oriented to accommodate the entry of the supporting cleats.

Abstract: The present invention relates to means for coupling the horizontally directed force of a seismic transducer into the earth with a downward going shear wave. The coupling means consists of a plurality of downwardly convergent wedge-shaped earth engaging cleats of differing depth mounted on the transducer support means. The lateral load-bearing surfaces of the cleats have sloping faces equally inclined to the vertical, so that they tend to compact and compress the earth to a similar degree with horizontal vibrator motion. However, on some or all of the cleats these sloping faces are interrupted by horizontal faces in a stair-case fashion so as to vary the overall sharpness of such cleats.

Abstract: A powerful seismic impulse is generated in a body of water by a slug of water propelled from a seismic source by expanding pressurized gas, but the gas is retained in the source for use in subsequent firings. The seismic energy source, which is called a "hydro gun", is recharged by pumping an incompressible liquid, preferably, water, at high pressure into the gun to compress the retained pressurized gas. The hydro gun includes a firing cylinder, and a piston follower in the firing cylinder divides it into a liquid-charge chamber and a gas-propulsion chamber. The liquid-charge chamber is closed from liquid discharge ports by a shuttle which is held closed by the high pressure of gas in an operating chamber. By pumping an incompressible liquid into the liquid-charge chamber, the follower is forced to compress the pressurized gas which is trapped in the gas-propulsion chamber.

Abstract: A marine seismic source employs a cylindrical gas exploder adapted to be supported from a surface vessel in a submerged state adjacent a marine bottom. The force of expanding gases within the exploder applies a thrust along the exploder longitudinal axis to a ground contact member operatively interconnected with the exploder to produce a seismic signal. The energy producing force is reacted by piston means within the exploder interconnected rigidly with a large area external water interacting disk. The mass of the reaction piston-disk system is sufficiently great so that the slow moving disk experiences viscous damping in the water and thus generates no significant undesirable secondary seismic signal in the water. The exploder may be oriented horizontally for maximum generation of shear waves or inclined at an acute angle to the vertical for generation of a combination of shear waves and compressional waves.

Abstract: An improved base plate for a vibratory seismic signal generator consists of a plurality of parallel T-bars welded together. The flange of every adjacent T-bar is inverted with respect to its neighbors.

Abstract: A system for controlling the tilt of the vehicle and vibrator when the vibrator is being operated on irregular surfaces. Tilt switches detect excessive vehicle tilt. A bleeder network activated by the tilt switches reduces the pressure in the air bag on the side of the vibrator opposite from the direction of the vehicle tilt. A supply network repressurizes the air bag on the side of the vibrator opposite from the direction of the tilt.

Abstract: A portable underwater signalling apparatus for use by divers having self-contained underwater breathing apparatus (scuba) to signal to other divers as well as surface and underwater vessels. The apparatus utilizes compressed air from the diver's tanks to drive a hammer against a diaphragm to cause sound waves to be transmitted through the water.

Abstract: A device for generating seismic waves in the earth employs an elongated open-ended barrel having its closed end adjustably supported on a base plate for inclinations with respect to the base from about 15.degree. to 30.degree. is also rotatable about an axis normal to the base. A cardboard tube with an interior waterproof coating and transverse dimensions complementary to the barrel is placed into the barrel so that its lower end is spaced from the closed end of the barrel. An explosive charge and a detonator are placed between the end of the barrel and the end of the tube. When the charge is detonated the resulting recoil impacts the base against the earth generating both compressional and shear waves which are recorded at a distance by a transverse seismometer. The barrel is then rotated through 180.degree. about an axis normal to the base and a second firing is made, generating compressional waves with the same phase and magnitude as the first firing and shear waves of equal magnitude but opposite phase.

Abstract: An accelerometer located on the pad of a vibratory seismic source provides a signal for comparison with the sweep signal which controls the vibrator. The error function representing the difference between the phases of these two signals is used to adjust the phase of the vibrator so as to maintain the vibrator in synchronism with the sweep signal. Prior to comparison with the sweep signal, the accelerometer output is conditioned by a tracking bandpass filter having its center frequency slaved to the instantaneous sweep frequency. Those components of the accelerometer output signal having a frequency equal to the instantaneous sweep frequency are passed by the bandpass filter and are subjected to approximately 0.degree. phase shift through the filter.

Abstract: An apparatus for generating a series of seismic acoustic pulses in a body of water. The series is characterized by having continuously-variable, non-repetitive time intervals between successive pulses during a continuous seismic recording. The preferred generator is an air gun comprising a variable-speed motor with a rotating cam for actuating a sleeve valve which alternately opens and closes exhaust ports in a high-pressure chamber. As the valve repeatedly opens, jets of high-pressure air are impulsively expelled into the surrounding water, thereby generating an underwater acoustic pulse train.

Abstract: A method of suppressing noise trains that develop from harmonics of a vibrator-type sweep signal. It includes the step of generating a plurality of such sweep signals in series and with the phase of each succeeding sweep signal being shifted relative to the previous one by a predetermined phase angle which is a fraction of 2.pi.. The generated signals are separately recorded and transformed by inverse phase shifting before being added or stacked in a conventional manner.

Abstract: A shear wave vibrator is constructed having a frame with first and second oppositely facing plenum chambers secured to the frame and each having an outer periphery. A skirt is attached to each of the outer peripheries. A fan is attached to the frame with conduits supplying a volume of air under pressure to each of the plenum chambers. A modulation apparatus is mounted in each of the first and second plenum chambers to cause a variation in air pressure in each of the plenum chambers in accordance with a predetermined signal in a manner to cause the air pressure in one chamber to decrease at the same instant the air pressure in the oppositely facing chamber is increasing and vice versa. The entire apparatus is mounted between opposite walls of a trench.

Abstract: An acoustical sparker probe apparatus is described for generating a high energy acoustical pulse at a frequency between 600 hz and 10 khz in a borehole having a diameter between 50 mm and 100 mm. The apparatus includes an uphole electronic system having a low voltage AC power source which is directed through an electrical cable to a borehole probe that is moved along the length of the borehole. The borehole probe has a sparker section with electrodes for generating a high energy acoustical pulse when a high energy electrical spark discharge is created between the electrodes. The probe has a high voltage DC energy section with a voltage multiplying and electrical energy storage for receiving the low voltage AC from uphole and creating and storing over 100 joules of electrical energy at a voltage above 1000 volts within the probe. The probe has a triggering network for rapidly discharging the high voltage electrical energy across the electrodes at above 5000 amp for 10 .mu.

Abstract: Disclosed is a seismic source forming part of a drill string which allows geological prospecting while drilling a borehole. The source includes a section of drill pipe having a spiral cam machined into its outer surface and a port for allowing mud to flow from the inside of the drill pipe into the borehole. A sleeve surrounds this section of the drill pipe and includes a cam follower, a plurality of ports, and a spring borehole contact for preventing rotation of the sleeve. The sleeve blocks flow of mud through the drill pipe port, except when a sleeve port is in alignment therewith. When the sleeve cam follower is engaged in the drill pipe cam and the drill pipe is rotated, the drill pipe port follows a helical path relative to the sleeve and sequentially passes all the ports in the sleeve. Signal wave shape is determined by the configuration of the sleeve ports and frequency is determined by the drill pipe rotation rate.

Abstract: An apparatus and method for generating seismic signals are described using a modulated vacuum within a chamber plus a compliant, vibration-isolating means. This compliant, vibration-isolating means provides a seal between the chamber and the earth, and also generally prevents the vibration of the chamber from being transferred to the earth. The seismic signal is transmitted directly to the earth by the changes in absolute air pressure within the chamber (the modulated vacuum). As the vibrations of the chamber are generally out of phase with the force developed by the changes in chamber pressure, the chamber vibrations must, for good efficiency, be isolated from the earth. This arrangement is lightweight and inexpensive, as there is no need for either a special mass to induce the vibrations or a special mass to hold the vibrating mass in contact with the earth's surface.

Abstract: A seismic exploration system for use on ice-covered waters is disclosed. The system comprises a housing which contains equipment such as an engine, a compressor, means for boring holes in the ice, and acoustic signal generating means that can be lowered into the water through holes in the ice. The housing is sufficiently lightweight that it easily can be transported from one location to another by helicopter or other aircraft. The heat generated by the engine is sufficient to provide a comfortable working environment for personnel within said housing and helps prevent freezing of equipment located within said housing.

Abstract: A transverse variable reluctance transducer of acoustic energy is configu to lend itself to being towed through the water while it radiates acoustic energy. Its elongate, cylindrical shape, which has an axial tunnel running its length, allows the flow of cooling water to prevent excessive heat from building up. The transducer's linear vibrator motor has its outer shell windings DC excited while the inner core or reciprocator has its windings AC excited. As the AC source is changed from one frequency range to another, responsive changes in the projected acoustic signal are radiated from suitably interconnected projection surfaces. In one configuration, one of the projection surfaces is in communication with the fluid flowing through the axial tunnel at one end of the transducer and another projection surface faces radially outwardly from the transducer's opposite end. Another configuration has both of these projection surfaces facing radially outwardly at opposite ends of the transducer.