Abstract: The underwater ear pod system is a multifunctional device that allows a user to listen to music and other audio signals transmitted through a transmitting device during underwater activities, while keeping water out of the swimmer or diver's ear. To accomplish this, the system comprises a waterproof earplug device and a well-connected communicating system, wherein the transmitting device may be positioned outside the water body or maintained floating over the surface of the water body, depending on the activity of the user. Further, the device can have emergency SOS signals automatically sent at predetermined intervals or on an as-needed basis based on button/touch inputs to add a layer of safety for swimmer's or divers. Furthermore, the device is compact, thereby facilitating portability and ease of storage. Thus, the underwater ear pod system is a multifunctional and cost-efficient ear pod system that can make aquatic activities more enjoyable, convenient, and safe.

Abstract: An electromagnetic shockwave transducer includes a double-faced coil of wire wound around an insulator. The coil has a first coil face on one side of the insulator and a second coil face on an opposite side of the insulator. Coil ends of the coil are electrically coupled to a current source, which produces a current pulse in the coil so as to produce a force between the coil faces.

Abstract: Provided is a speaker box, including a speaker, comprises a frame, a first vibration system and a magnetic circuit system fixed on the frame; the first vibration system providing a diaphragm vibrate along a first direction; a housing with an accommodation space, includes: a bottom wall facing the diaphragm, and a sidewall bending and extending from an outer edge of the bottom wall; wherein the speaker received in the accommodation space, and the frame of the speaker comprises a split body of a first frame and a second frame, the second frame extends and fixed to the sidewall.

Abstract: A method of treatment includes using an electrical energizing source coupled to a current conducting coil to cause the current conducting coil to produce pulsed electromagnetic fields. A conducting membrane is placed adjacent the current conducting coil and an insulating coupling interface is placed adjacent the membrane, such that the membrane is between the current conducting coil and the insulating coupling interface. One portion of the pulsed electromagnetic fields is intercepted by the membrane so that the membrane oscillates to generate acoustic waves to tissue adjacent the insulating coupling interface and another portion of the pulsed electromagnetic fields propagates through the insulating coupling interface to the tissue.

Abstract: This invention claims a patent on the process of propagating soundwaves through bodies of water, such as oceans, to produce and direct winds, for the purpose of managing aerial weather systems. Propagating soundwaves within water can generate and direct wind for many purposes. One purpose is to effectively weaken storms, by directing wind-shear against a storm's momentum, and stripping it of precipitation. Another purpose is to guide atmospheric rivers, and manually re-direct clouds in the precipitation cycle. This inventive process grants methods to mitigate dangerous weather patterns, such as droughts and hurricanes. The invention introduces a new subject matter that distinguishes it from other inventions relevant to underwater acoustics: manual processes to moderate weather.

Abstract: The present disclosure relates to a device for generating shock waves that includes an interchangeable applicator head for generating shock waves for treatment of human or animal bodies, which applicator head includes a reflection or focusing mechanism, two electrode tips for producing a spark gap, and a membrane, which together with the reflection or focusing mechanism encloses a fluid medium that is designed to generate a plasma when a voltage between 1 kV and 30 kV is applied. According to the disclosure, the applicator head is electrically and mechanically connected to a hand-held apparatus in a detachable manner.

Abstract: Mechanical transducers efficiently produce and couple high-power acoustic pulses into liquid and solid media. In a transmitter, mechanical excitation of a thin transmitting plate is provided by an actuator or a motor that causes a mass to strike or a drive rod to push the thin plate. If struck, as the thin plate rings down, it delivers much of its kinetic energy to acoustic radiation in the dense medium. Different mechanisms may be used to excite the plate, and different mechanisms may be used to couple the plate excitations into dense media. Conditions are found for efficient transduction of mechanical energy by a thin plate into acoustic radiation in solid and liquid media. A receiver comprises a plate having matching resonances to the transmitting plate. Discrete narrowband frequencies of acoustic signals are used to detect phase changes in waves reflected from a moving object.

Abstract: Embodiments relate to relate to marine vibrators that incorporate one or more piston plates that act on the surrounding water to produce acoustic energy. An example marine vibrator may comprise: a containment housing; a piston plate; a fixture coupled to the containment housing; a mechanical spring element coupled to the piston plate and the fixture; a driver disposed in the marine vibrator, wherein the driver is coupled to the piston plate and the fixture; and a container coupled to the piston plate, wherein the container is configured to hold a variable mass load; wherein the marine vibrator has a resonance frequency selectable based at least in part on the variable mass load.

Abstract: A system includes a data storage medium and a shockwave generator. The data storage medium includes cells and a plurality of layers. Each cell is configured to store information therein. At least two cells are arranged in a horizontal plane within a same layer of the plurality of layers of the data storage medium and at least two cells are arranged in a vertical plane in different layers of the plurality of layers of the data storage medium. The shockwave generator is configured to generate a shockwave signal that travels through a layer of the plurality of layers of the data storage medium. A target cell within the layer stores information responsive to a beam emitted from an emitter targeting the target cell as the shockwave signal is passing through the target cell. The target cell maintains the information after the shockwave signal exits through the target cell.

Abstract: An acoustic transmitter includes: an acoustic diaphragm configured to transmit acoustic waves into a medium; a piezoelectric actuator assembly configured to deform in an axial direction in response to an applied electrical signal; and a highly incompressible elastic material disposed between the piezoelectric actuator and the acoustic diaphragm and configured to transmit pressure waves to the acoustic diaphragm in response to motion of the piezoelectric actuator.

Abstract: Disclosed are electromagnetic linear actuators used in acoustic vibratory sources for marine seismic surveying. An embodiment discloses a linear actuator for acoustic sources, comprising: magnetic circuitry comprising a gap; and a coil assembly comprising: a drive coil, wherein at least a first portion of the drive coil is configured to be moved in a linear path in the gap; a pair of ferromagnetic coil guides positioned on either side of the linear path; a first ferromagnetic extension extending laterally from the first portion of the drive coil; and a transmission element coupled to a top side of the first portion of the drive coil. Embodiments also disclose acoustic vibratory sources, marine seismic survey systems, and methods of marine seismic surveying.

Abstract: A seismic source includes a flextensional shell defining a longer axis and a shorter axis and at least one driver coupled to the flextensional shell proximate an end of the shorter axis. The seismic source may be a component of a marine seismic survey system. The marine seismic survey system may be utilized in a method of marine seismic surveying.

Abstract: An ultrasound system that detects a characteristic of an ultrasound wave. The system includes a circuit member defining a sensing portion operable to be exposed to the ultrasound wave. The system also includes a current generating device that generates a current in the sensing portion of the circuit member. Furthermore, the system includes a voltage sensor that detects a voltage across the sensing portion due to the exposure to the ultrasound wave to thereby detect the characteristic of the ultrasound wave.

Abstract: An electro-dynamic acoustic projector provides a rigid enclosure having an open end. A pressure compensated chamber extends into the rigid enclosure from the open end. A vibratile piston is located in the open end of the rigid enclosure and closed the pressure compensated chamber. The vibratile piston has an axis of oscillation perpendicular to the plane of the open end and an anterior major surface exposed from the open end for generating sound waves in water. A magnet assembly is attached to the vibratile piston which interacts with a stator coil positioned with respect the rigid enclosure and vibratile piston. The magnet assembly is affixed to a posterior surface of the vibratile piston. The magnet assembly comprises first and second permanent magnets located with respect to one another to bring like poles into facing opposition. The facing like poles are separated from one another by a ferromagnetic focus element.

Abstract: The electromagnetic acoustic transducer (EMAT) transducer disclosed herein is useful for the non-destructive analysis of objects. The transducer comprises a core having a winding and a coil disposed between the core and the object to be analyzed. One transducer can be used as a transmitter and another transducer as a receiver. Then selectively switching static magnetic field in either transmitter or receiver and processing data with and without static magnetic field allows for eliminating artifacts due to parasitic coupling between the transmitter/receiver pair. The switching of the static magnetic field can be implemented either by using electromagnet or a pair of permanent magnets where magnetization of one permanent magnet is reversed to provide cancellation of the static magnetic field.

Abstract: A portable low frequency underwater acoustic projector having two circular diaphragms separated by a spacer ring with a pair of coils and oscillating masses being located in pipes connected to central opening in two diaphragms, the coils driving these masses in opposite directions. Central openings in each diaphragm have an associated pipe extending outward from the interior of the projector, the pipe having closed outer ends. The interior of the projector being gas filled to provide pressure compensation.

Abstract: A boomer for generating acoustic signals in a marine seismic survey has a frame towed by a survey vessel. A coil is mounted to the frame and a conductive plate is adjacent to the coil. A capacitor is mounted to the frame, and control electronics system delivers an electric charge stored in the capacitor to the coil. The invention obviates the need for heavy conductive cables between the survey vessel and the boomer in conventional systems where the capacitors are carried by the vessel, while maintaining the desirable acoustic properties of the boomer.

Abstract: Systems and methods of the invention can equalize the pressure between an interior cavity and an environment exterior to the interior cavity, while providing for acoustic isolation between the two environments so that acoustic energy propagating through one environment does not cause acoustic vibrations in the other environment. In one application, these pressure compensation systems are employed to equalize the pressure on either side of a moving coil projector, thereby reducing the deleterious effect that a pressure differential across the moving coil projector can have on the operation of the moving coil projector and reducing the likelihood that propagating acoustic energy can result in phase cancellation that reduces the acoustic performance of the moving coil projector.

Abstract: A sound generating device for generating a sound wave in a body of water is provided. The device includes a pair of axially aligned pistons. An electromagnet is mounted on at least one of the pistons. Activation of the electromagnet causes the pistons to move towards each other. A spring is positioned between the pistons and biases the pistons away from each other. Provision is made for changing the spring rate during operation so that the device will operate at mechanical resonance throughout the intended frequency range. A control device controls the current flowing through the electromagnets. The current is controlled to induce a predetermined variance of axial displacement between the pistons and thereby generate a sound wave.

Abstract: Shock wave source based on the electromagnetic principle with defined focusing, with an electrically conductive, three-dimensionally curved membrane, with a coil, which is located adjacent thereto and to which current pulses can be admitted. A switchable electric connection is provided between the coil and a power supply unit. A housing is provided accommodating the membrane and the coil embedded in a coil form, between which housing and the membrane the coil form is located. A transmission medium is provided adjacent to the membrane and exerts pressure on the membrane. The coil form is made deformable and elastically compressible and is installed in the compressed state. The installed amount of the transmission medium remains unaffected during the operating state after the assembly.

Abstract: An elongated, electrically conductive diaphragm is placed in a strongly magnetic field to produce a linear and an elongated sound source giving a high sound energy. At least two elongated diaphragms are positioned between intermediate and enclosing protected magnet elements, whereby the transverse length of the diaphragms are at least of the same size as that of the intermediate protected magnet elements. In this way, a sound without considerable interference merges at a short distance from the sources of the sound. By placing additional such sources of sound alongside each other, a broad sound source with a surface producing an essentially homogeneous sound field is achieved.

Abstract: A sounder has a first plate 1 that is molded into a lower case. The first plate functions not only as part of a magnetic circuit, but also as a terminal on the outside of the sounder. The first plate has a coil positioned around a center pole on the first plate and a coil connector for attachment to an end of the coil. A second plate 5 is molded into the lower case and also has a coil connector for attachment to another end of the coil. Accordingly, both ends of the coil can be coupled to the connectors on the inside of the sounder. With this arrangement, the outside of the plates are conductive to an outside connector terminal, thereby eliminating having to pull out both ends of the coil from behind the plates.

Abstract: An automated method for winding a coil of an electroacoustic transducer utilizes a support member that has a frusto-conical projection for receiving an outer pole tip. The frusto-conical configuration assures that, upon completion of a coil winding about the pole, there is an exposed recess around the periphery of the pole tip. This is accompanied by an end surface of the winding being coplanar with the corresponding end surface of the pole tip. Maximized performance for the transducer may then be realized.

Abstract: The present invention provides an electroacoustic transducer which can increase the winding efficiency of a coil on a pole and allows the automation of a coil winding process. The present invention relates to an electroacoustic transducer for vibrating a diaphragm by a magnetic field generated in response to an inputted electric signal to convert the electric signal into sound. The coil is wound around the pole along its entire length. However, at the pole tip, the coil is formed to have an outwardly diverging, frusto-conical recess that exposes the pole tip.

Abstract: The present invention provides a fabrication method of an electroacoustic transducer capable of simplifying an assembling process on a lead frame and realizing an automatic assembly. The method comprises steps of forming pole piece portions, forming a lead frame having a plurality of base forming areas thereon, each of the areas having lead terminals formed therein, forming bases of a synthetic resin on the lead frame by molding so that the pole piece portions are embedded in the bases, mounting a coil on the pole piece portions embedded in the bases, disposing a support ring and a magnet so as to surround the coil, and placing a diaphragm on the support ring to be held thereby, connecting opposite ends of the coil to the lead terminals, cutting off the lead terminals from the lead frame, putting cases on and fixedly joining the same to the bases, and subjecting the cut lead terminals to a forming process.

Abstract: An anti-fouling system for producing vibrations in an underwater structure to inhibit the attachment of aquatic life forms to the structure. The system includes a controller which drives one or more transducer. The transducer comprises a housing, one end of which is closed by a resilient diaphragm. An electromagnet with soft magnetic core is contained in the housing spaced from an unsupported portion of the diaphragm. The unsupported portion of the diaphragm is mounted over an underwater structure. In operation, the electromagnet is excited with a current pulse, which deforms the diaphragm so that the housing moves towards the structure. As the current drops off, the diaphragm is restored to its original shape and the housing moves away from the structure imparting a vibrational force to the structure. The transducer includes an elastic membrane to compensate for changes in temperature and pressure commonly found when working under water.

Abstract: A method and apparatus for increasing the density and strength of bone, particularly for preventing or treating osteoporosis, by subjecting the bone to unfocussed compressional shock waves.

Abstract: An electrodynamic transducer has a diaphragm substantially having two parts with different profiles, namely an acoustically active central part and an annular part laterally adjoining the central part and serving for the resilient suspension of the diaphragm in its entirety. A narrow coil seat for a wire coil of the transducer is located between the central part and the annular part. For the purpose of developing a compact yet electrodynamically sensitive acoustic transducer, the annular part is not arranged radially outside the central part of the diaphragm, but is shifted inward according to the invention. The curved annular part is thus accommodated under the axial curvature of the central part. The annular part can therefore have the annular width required for an ideal resilient suspension without negatively affecting the outer dimensions of the transducer.

Abstract: In an electroacoustic transducer, the opening portion of a casing body which contains therein a magnetic driving portion for converting an electric signal into a sound is closed by a casing cap to form a resonance space (resonance chamber) which resonates in response to an acoustic vibration generated by the magnetic driving portion, wherein a plurality of slender projections to be entered into said casing body are projected from the casing cap to position said casing cap relative to said casing body. As a result, it is possible to enlarge the capacity of the resonance chamber and improve the assembling accuracy.

Abstract: An acoustic projector wherein a unitary acoustic resonator produces active sonar signals in more than one frequency band. The double-slotted resonator is coupled to a transducer which is capable of exciting the resonator in two, distinct, volumetric modes of vibration using two asymmetric, generally arcuate vibrating members. Transduction techniques can include variable reluctance or piezoceramic transduction. Internal cavity pressure release may be achieved by bladders, compliant tubes, and the like.

Abstract: An electroacoustic transducer having a diaphragm and a magnetic driving portion respectively housed in a housing wherein the magnetic driving portion vibrates the diaphragm magnetically in response to an electric signal. A base member for closing an opening at the rear side of the housing is formed of a metallic plate. Lead portions are provided by extending both ends of a coil of the magnetic driving portion. Terminal patterns are formed on a surface of the base member with an insulating film between them. The lead portions of the coil of the magnetic drive portion are connected to the terminal patterns.

Abstract: An apparatus for generating acoustic pressure pulses in an acoustic medium has a membrane that can be driven which adjoins the acoustic medium and which is driven in an impact-producing manner. The membrane is mechanically pre-stressed so that it returns into its initial position after a pressure pulse is generated.

Abstract: An electroacoustic transducer converts an electric signal into sound by vibrating a diaphragm magnetically in response to the electric signal input thereto. A movement restricting means for restricting the movement of the diaphragm within an allowable movement range is provided on the inner wall of a resonant chamber disposed at one side of the diaphragm. The restricting means normally confronts at a magnetic member attached to the center of the diaphragm. The restriction means contacts the magnetic member when the diaphragm attempts a deflection beyond the allowable range.

Abstract: A sonar transmitter includes a source means for providing an actuation signal to drive an electromagnetic transducer projector without the use of bias magnetization. The invention utilizes an offset actuation frequency technique in which electrical driving signals are applied which have a frequency or frequencies other than the desired frequency of the acoustic signal projected into a liquid medium. In presently preferred embodiments, one or two driving signals may be utilized. If one driving signal is utilized, the acoustic signal will be at twice the driving signal frequency. If two driving signals are utilized, the acoustic signal will be at the sum or difference frequency of the driving signal frequency. The actuation signal is applied to coils of the transducer's electromagnets to produce an electromagnetic attractive force having a significant component at the desired frequency of the acoustic signal.

Abstract: An electromagnetic pressure pulse source for generating focused pressure pulses as an electrically conductive membrane and a coil system which drives the membrane by rapidly displacing the membrane from the coil system. The coil system is formed by an annular array having a number of annular zones which can be individually activated to cause the generation of pressure pulses in variable chronological relation to each other, which permits the location of the focus of the resulting shockwave to be adjusted with a range, and/or the diameter of the focus to be changed.

Abstract: The present invention involves a moving-coil electrodynamic electroacoustical transducer, comprising a disk made of a hard, nonmagnetic material (12), which is superimposed on the diaphragm (11) and has openings for the output of sound, a power-factor-improvement device/super charger (13) made of a nonmagnetic material which is placed in the concavity of the diaphragm (11) and which has annular, concentric ducts (13') having a conical shape, and a cover (14) made of a nonmagnetic material serving as the lid in both configurations of the transducer, the said cover being applied to the body facing the concavity of the said diaphragm in a direct-radiation transducer, while it is applied to the body facing the convexity of the said magnetic disk (12) in an indirect-radiation transducer.

Abstract: A pressure pulse generator has a pressure pulse source with a membrane that is rapidly displaceable from an initial position for generating acoustic pressure pulses in an acoustic propagation medium. For returning the membrane to its initial position, the acoustic propagation medium adjoining the membrane is maintained at an elevated static pressure in comparison to the ambient pressure. Additionally, a cooling arrangement for the pressure pulse source is provided for eliminating the dissipated heat arising during operation of the pressure pulse source. The cooling system contains a coolant that flows in a closed circulation path through a channel integrated into the pressure pulse source and through a cooling unit.

Abstract: The composite electroacoustic transducer for reproducing medium and high frequencies comprises a transducer assigned to reproducing midrange frequencies provided with a dome-shaped membrane which extends in an annular shape. A transducer assigned to reproducing high frequencies is provided with a dome-shaped membrane and is arranged coaxially to the center of the transducer assigned to reproducing midrange frequencies.

Abstract: A variable reluctance acoustic projector includes a piston structure that provides rigid retention and precise alignment of electromagnetic cores within the projector housing. The piston structure provides a pair of metallic piston blocks having cavities in which the electromagnetic cores are mounted. The piston blocks rigidly retain the electromagnetic cores within the cavities by compressive loading, improving the structural reliability of the device. In addition, the piston blocks enable precise alignment and orientation of the pole faces of opposing electromagnetic cores parallel to one another. Flexure ribs formed in the piston blocks increase the compliance of the blocks to substantially confine motion of the piston blocks to translation along a single axis of actuation during excitation of the electromagnetic cores.

Abstract: An electromechanical transducer having permanent magnet means forming a bias field in a region between poles, and a vibratable armature having a first part in that region. The armature has a second part extending from the first part substantially externally of that region. Magnetically permeable structure includes a portion opposing the second part across a transverse gap. The latter structure is included in a closed magnetic loop comprising said first and second parts, a working gap in said region and the transverse gap, and an electrical signal coil is threaded by the loop.

Abstract: A pressure pulse source, of the type suitable for generating shockwaves, has a positive lens for focusing the pressure pulses onto a focal zone. The positive lens has an acoustic exit face which has a shape, in a focusing zone, for focusing the pressure pulses and a shape, in at least one measurement zone, which deviates from the shape in the focusing zone. A pressure sensor containing a piezoelectric polymer foil is disposed at the measurement zone. The pressure sensor, or a number of such pressure sensors, generate signals which are used to monitor the pressure pulses emerging from the positive lens, such as by acquiring their peak value.

Abstract: A flexural transducer includes a hollow tube that is magnetically driven by a coil/magnet assembly. A magnetic field is provided by passing a current through the coil. The filed passes through an air gap between the coil and the magnet to attract and repel the magnet during alternating portions of the current's cycle. The magnetic transducer driver mechanism permits high drive capability, high temperature operation and provides lower frequency operation than conventional ceramic drivers.

Abstract: A pressure pulse generator has an electromagnetic pressure pulse source which includes a coil arrangement for driving an electrically conductive membrane. The coil arrangement is divided into a first annular coil section and a second annular coil section, the second annular coil section surrounding the first annular coil section. The respective ends of the coil sections are maintained at respective electrical potentials so that, upon activation of the pressure pulse generator to generate pressure pulses, voltage arcing between the respective ends of the coil sections and components adjacent thereto is precluded.

Abstract: An electrically driveable shockwave source for generating acoustic shockwaves of the type suitable for medical therapy, as a coil arrangement and a membrane disposed adjacent the coil arrangement. The membrane and/or the coil arrangement is formed by a multi-layer structure, with each layer having electrically conductive elements therein insulated from each other, in the form of electrically conductive sections in the membrane, or electrically conductive windings connected in parallel in the coil arrangement.

Abstract: An acoustic pressure pulse generator has an electrodynamic pressure pulse source formed by a membrane and a coil, so that when the membrane is electrodynamically rapidly repelled from the coil, an acoustic pressure pulse is generated in an acoustic propagation medium adjacent the membrane. A wall is disposed in the pulse generator spaced from the membrane in the direction of pressure pulse propagation, the wall preferably formed as an acoustic lens. The wall defines a space between the wall and the membrane, which is filled with acoustic propagation medium, and which is maintained liquid-tight from a second space situated at the other side of the wall, also containing an acoustic propagation medium. The acoustic propagation medium contained in the first space is maintained at a static pressure which is necessary for returning the membrane to its initial position after being repelled by the coil.

Abstract: In the underwater sound source disclosed herein, rigid diaphragms are provided at opposed ends of a hollow shell, the periphery of each of the diaphragms being sealed to the shell. Respective spring means operating between the shell and each of the diaphragms allows axial displacement of the diaphragm in response to external pressure. A lightweight magnetic armature structure is connected to each of the diaphragms and opposed electromagnetic core structures provide magnetic circuits which link each of the armature structures across respective gaps. Further spring means are provided for centering each of the armature structures between the respective magnetic core structures. By appropriately energizing windings on the magnetic core structures, the armatures together with their respective diaphragms are caused to oscillate.

Abstract: A sonar projector having a pair of opposed oscillating pistons driven by an electromagnetic assembly is provided with reduced weight and high power by forming the electromagnetic assembly with a permanent magnet structure consisting of two coaxial longitudinally juxtaposed members each having permanent magnets radially poled oppositely to the permanent magnets of the other coaxial member, each of the permanent magnets of one coaxial member forming a series magnetic circuit with one of the permanent magnets of the other coaxial member. As a result of this arrangement, the amount of iron required for pole pieces of the electromagnetic assembly is reduced without reducing power. Furthermore, the size or volume is also reduced as compared to an equivalent projector.

Abstract: A shockwave source and generating device includes a ring shaped or cylindrical wave generator having a central axis for radiating shockwaves in an axial direction or radially towards a parabolic reflector so that any yet unreflected radiation from the generator is intercepted by the reflector and reflected towards a focal point on that axis.

Abstract: An electrodynamic shockwave generator, of the type having a shockwave source formed by an electrically conductive membrane and an electrically driven coil, with the membrane being rapidly repulsed from the coil, causing the creation of a shockwave in an acoustic propagation medium disposed on one side of the membrane, upon the application of a pulse to the coil, wherein at least one of the coil or the membrane contains material which can be placed in a superconducting condition. A coolant, and a member for circulating the coolant are provided for placing the material in at least one of these electrically conductive elements in the superconducting condition.

Abstract: The present invention provides a fabrication method of an electroacoustic transducer capable of simplifying an assembling process on a lead frame and realizing an automatic assembly. The method comprises steps of forming pole piece portions, forming a lead frame having a plurality of base forming areas thereon, each of the areas having lead terminals formed therein, forming bases of a synthetic resin on the lead frame by molding so that the pole piece portions are embedded in the bases, mounting a coil on the pole piece portions embedded in the bases, disposing a support ring and a magnet so as to surround the coil, and placing a diaphragm on the support ring to be held thereby, connecting opposite ends of the coil to the lead terminals, cutting off the lead terminals from the lead frame, putting cases on and fixedly joining the same to the bases, and subjecting the cut lead terminals to a forming process.