US3302163A - Broad band acoustic transducer - Google Patents

Broad band acoustic transducer Download PDF

Info

Publication number
US3302163A
US3302163A US484134A US48413465A US3302163A US 3302163 A US3302163 A US 3302163A US 484134 A US484134 A US 484134A US 48413465 A US48413465 A US 48413465A US 3302163 A US3302163 A US 3302163A
Authority
US
United States
Prior art keywords
cylindrical
conical
phase
waves
reflectors
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US484134A
Inventor
Jr Daniel E Andrews
Original Assignee
Jr Daniel E Andrews
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Jr Daniel E Andrews filed Critical Jr Daniel E Andrews
Priority to US484134A priority Critical patent/US3302163A/en
Application granted granted Critical
Publication of US3302163A publication Critical patent/US3302163A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • GPHYSICS
    • G10MUSICAL INSTRUMENTS; ACOUSTICS
    • G10KSOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/18Methods or devices for transmitting, conducting, or directing sound
    • G10K11/26Sound-focusing or directing, e.g. scanning
    • G10K11/28Sound-focusing or directing, e.g. scanning using reflection, e.g. parabolic reflector
    • GPHYSICS
    • G10MUSICAL INSTRUMENTS; ACOUSTICS
    • G10KSOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/18Methods or devices for transmitting, conducting, or directing sound
    • G10K11/20Reflecting arrangements

Description

' Jan. 31, 1967 D. E. ANDREWS, JR 3,302,163
BROAD BAND ACOUSTIC TRANSDUCER Filed Aug. 31, 1965 INVENTOR. DAN/EL E. ANDREWS, JR
United States Patent M 3,302,163 BROAD BAND ACOUSTIC TRANSDUCER Daniel E. Andrews, Jr., 1563 Yost Drive, San Diego, Calif. 92109 Filed Aug. 31, 1965, Ser. No. 484,134 13 Claims. (Cl. 3408) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
This invention relates both to transducers for converting oscillatory electrical energy into acoustic waves, and to those for converting acoustic waves into electrical energy, and, in particular, to those transducers especially adapted for underwater sound applications.
Efforts heretofore to increase the bandwidth of directional underwater acoustic transducers and especially or transducers used as sources of underwater sound, have left much to be desired. Some progress has been made through the use of piezoelectric and magnetostrictive cylinders arranged in linear arrays both with and without reflectors and through the employment of mass-loaded piezoelectric stacks in plane and curved arrays, but frequently either the bandwidth or the directional properties are not adequate. Also, the cost of the mass-loaded ele ments is often prohibitive.
It is therefore a primary object of this invention to provide an improved and relatively inexpensive transducer having a relatively broad frequency response.
Another object is to provide a transducer having an improved directional response and one that is suitable for use both singly and in arrays.
According to the present invention a hollow, generallycylindrical electromechanical transducer element is mounted concentrically between a pair of conical reflectors one of which has a relatively hard surface radially facing the cylindrical transducer element, while the other has a similarly-disposed relatively soft surface.
It is recognized that the fundamental radial mode of vibration 'of a hollow circular cylinder immersed in a fluid produces vibrations in the fluid at the inner and outer surfaces of the cylinder, the two sets of vibrations being in exact phase opposition. For example,'if an electromechanical (magnetostrictive, piezoelectric or other) cylinder is electrically driven at some frequency in the vicinity of or below that of its fundamental radial mode, movement of its inner surface will tend to rarefy the enclosed medium whenever the movement of the outer surface tends to compress the medium surrounding it, and vice versa.
As already stated, the presentinvention is capable of operating either in a receiving or a radiating mode, although the apparatus normally would be adapted for both modes. In a radiating mode, oscillatory electrical energy is supplied to the transducer element to produce the compressional and rarefactional waves which travel radially and are reflected outwardly by the conical reflectors, preferably in a direction axially aligned with the cylindrical transducer. However, the reflection-s, instead of maintaining the out-of-phase relationship, are in phase due to the relative acoustic impedance of the soft-surfaced reflector which is such as to produce a phase reversal in its reflections, as well as the impedance of the hard-surfaced reflector which is such as to preserve the phase of its impinging waves. Inasmuch as this arrangement acoustically loads both the inner and outer surfaces of the radiating cylinder, "better coupling, bandwidth and .efficiency is obtained. Also the large elfective aperture 3,302,163 Patented Jan. 31, 1967 (nominally twice the wall thickness plus four times the height of the cylinder) provides useful directional characteristics. In addition, the bandwidth is further enhanced by the boost in response at low frequencies due to a resonant-pipe effect, the effective length of the pipe being equal to twice the cylinder height plus half the wave length being considered.
In its receiving mode, in-phase incoming acoustic waves have their phase relationship reversed with the result that their energy, impinging on the cylindrical transducers produces a mechanical vibration which, in turn, produces an electrical output.
Other objects and features of this invention will become apparent to those skilled in the art by referring to the specific embodiment described in the following specifications and shown in the accompanying drawing in which the single figure comprises a half section of a round transducer body incorporating this invention.
Referring to the drawing, transducer element 10 is a hollow cylinder of electromechanically-active material which will radially expand and contract when stimulated by an electric field or will generate an electric output when subjected to a radial mechanical stress. The cylinder may be fabricated from one piece or an assembly of pieces, all or only part of which may be electromechanically active. Typically, ferroelectric ceramics, such as barium titanate and lead zirconate, and scrolls or stacks of rings made of magnetostrictive material are used although assemblies made of crystals of Rochelle salt amonium-dihydrogen-phosphate, or quartz or other electromechanically active substances can be employed. In the example shown, element 10 is a radially polarized ferroelectric ceramic cylinder, the cylindrical surfaces of which are covered with fired-on silver electrodes, 11 and 12. Insulated electrical leads 13 are electrically connected by soldering or other suitable means to these electrodes. When an alternating voltage is applied to the leads and to the electrodes 11 and 12 the diameter of the cylinder 10 alternately increases and decreases in rhythm with the applied wave. Conversely, when a soundwave impinges upon the sides of the cylinder so as to create time-varying stresses in the material, a corresponding electric signal, which can be measured across the terminals 13A, is generated.
Two conical reflecting surfaces 20 and 21 are disposed opposite inner and outer radiating surfaces 11A and 12A of the transducing element 10. According to an important feature of this invention, one reflecting surface presents a very high acoustic impedance while the other reflecting surface presents a very low one. It is immaterial whether the high impedance surface is inside or outside the cylindrical transducing element. In the specific example illustrated, a high impedance right'circular conical reflector 20 having an apex angle of and a height equal to the height of the cylinder 10 is mounted coaxially within the cylinder. The apex falls in or close to a plane through the top rim of the cylinder. Mounted coaxially outside the cylinder is a low impedance, truncated 90 right circular reflector 21, the smaller inner circle of which coincides with the outer lower rim of the cylinder.
Preferably, the upper rim of cone 21 extends beyond the top rim of the cylinder 10. The inner surface of the conical member 21 is made to have a very low acoustic impedance 'by covering it with a soft pressure release material 21A having high compliance at the power and frequencies of operation. The acoustically soft material may be a corkor gas-impregnated elastomer such as the commercially available materials known as Corprene or Celtite rubber. The material is of substantial thickness and is preferably backed by a supporting structural conical member 21B. Conical structure 2113 conveniently supports inner cone and the cylinder 10, and it, in turn, is supported in an appropriate housing 22. A plate 23 is bolted across the end of the housing and contains a water-tight gland 24 used to eifect the seal between the case in a lead-in cable 13.
As the cylinder vibrates in its radial mode in response to the application of the alternating electrical power, the cylinder goes through alternate expansions and contractions. When the cylinder contracts, a radial compressional wave is radiated inwardly toward the inner reflecting surface 20 While a rarefractional cylindrical wave is radiated radially outward toward the outer reflector. On striking the inner reflector the cylindrical wave is converted by reflection into a plane wave traveling outward along the axis of the cone and the time phase of the pressure wave is preserved on its reflection from the high impedance surface. On striking the outer reflector 21, the outgoing cylindrical wave is converted by reflection into a plane wave also traveling outward along the axis of the cone, but with the phase of the outgoing disturbance being rcversed by 180". Because of this phase reversal and the overall geometry of the system both reflected waves arrive at the mouth of the tranducer at the same time and in phase. The in-phase addition of the two reflections maintains irrespective of the frequency and amplitude of the excursions of the vibrating cylinder as long as the specific acoustic impedance of the two reflecting surfaces are respectively many times greater and many times less than that of the propagating medium or, in other words, the ambient environs of the transducer. Line 30, which is perpendicular to the face of, and is the axis of symmetry for, the transducer assembly, is the direction of maximum respouse for outgoing or incoming acoustical signals. The in-phase additions cause the transducer to perform much as though it were a shaded, piston-type radiator. The annular spaces surrounding the cylindrical element may be filled with oil or a suitable potting compound, transparent to acoustical energy, or the electrical parts may be insulated by coating them with an insulating material and the annular spaces exposed to the surrounding fluid.
It will be recognized that the foregoing description has been principally with regard to a transducer adapted to convert oscillatory electrical energy into an outgoing acoustic wave. However, as has been stated, the transducer easily is adapted for the conversion of acoustic wave energy into an electrical signal. In this latter event, the acoustic wave arrives at the reflectors in phase and then the phase reversal of the relatively soft reflector produces an out-of-phase relationship which mechanically vibrates the cylinder to produce the electrical signal.
The structural parts of the transducer assembly preferably are made of corrosion resistant metals such as copper, brass or stainless steel. Although corkor gasfilled rubber-like materials are usually used for the pressure release layer 21, assemblies of compliant tubes, gasfilled bladders, and other pads and pressure-release devices known to the art may be used.
Modifications may be made in the proportions or relative dispositions of the assembly without departing from the scope of the appended claims.
What is claimed is:
1. Acoustically responsive apparatus comprising;
an electromechanical transducer element having a hollow generally-cylindrical shape;
a conical reflector disposed concentrically and exteriorally of said cylindrical element;
a second conical reflector disposed concentrically and interiorally of said cylindrical element, the two conical reflectors being disposed to reflect waves in one direction parallel to the axis of said cylindrical element and being equally spaced from the opposed surfaces of said cylindrical element so that the distances in wave lengths along any radial line to corresponding incremental areas on the conical reflector surfaces are substantially equal;
one of said conical reflectors having a relatively hard and noncompliant surface radially facing said cylindrical element and the other of said reflectors having a relatively soft and compliant surface radially facing said cylindrical element;
said relatively hard surface having an acoustic impedance sufliciently higher than its operative ambient environs for substantially preserving the phase of impinging acoustic waves and the other surface having an acoustic impedance sufliciently lower than said environs for substantially reversing the phase of impinging waves.
2. The apparatus of claim 1 wherein said second conical reflector is formed as a right circular cone of a height approximately equal to the height of said cylindrical transducer element.
3. The apparatus of claim 2 wherein said cylindrical element has a height approximately equal to one half of its inside diameter.
4. The apparatus of claim 3 wherein said exteriorallydisposed conical reflector is formed as a truncated right circular cone having an apex angle of 90 and having its smaller diameter approximately equal to the outer diameter of said cylindrical transducer element.
5. The apparatus of claim 1 wherein said exteriorallydisposed reflector is provided with said soft and compliant surface.
6. Acoustically responsive apparatus comprising;
an electromechanical transducer element having a hollow generally-cylindrical shape;
electrical means operatively coupled to said cylindrical element for producing an alternating radial motion of the cylinder whereby radially-directed compressional and rarefractional acoustic waves generated from the inner and outer surfaces of said cylindrical element are substantially out of phase;
a conical reflector disposed concentrically and exteriorally of said cylindrical element;
a second conical reflector disposed concentrically and interiorally of said cylindrical element, the two conical reflectors 'being disposed to reflect said acoustical waves in one direction parallel to the axis of the cylindrical element and being equally spaced from the opposed surfaces of the cylindrical element so that the distances in wave lengths along any radial line to corresponding incremental areas on the conical reflector surfaces are substantially equal;
one of said conical reflectors having a relatively hard and noncompliant surface radially facing said cylindrical element and the other of said reflectors having a relatively soft and compliant surface radially facing said cylindrical element;
said relatively hard surface having an acoustic impedance sufliciently higher than its operative ambient environs for substantially preserving the phase of impinging acoustic waves and the other surface having an acoustic impedance sufficiently lower than said environs for substantially reversing the phase of impinging waves;
whereby said acoustic waves reflected from said surfaces are effectively in phase in said one directional parallel to said axis.
7. The apparatus of claim 6 wherein said second conical reflector is formed as a 90 right circular cone of a height approximately equal to the height of said cylindrical transducer element.
8. The apparatus of claim 7 wherein said cylindrical element has a height approximately equal to one half of its inside diameter.
9. The apparatus of claim 8 wherein said exteriorallydisposed conical reflector is formed as a truncated right References Cited by the Examiner UNITED STATES PATENTS 2,005,741 6/ 1935 Hayes 34016 2,746,026 5/ 1956 Camp 340-8 References Cited by the Applicant UNITED STATES PATENTS 3,027,964 6/ 1958 Spragins.
10 CHEST-ER L. JUSTUS, Examiner.
I. P. MORRIS, Assistant Examiner.

Claims (1)

1. ACOUSTICALLY RESPONSIVE APPARATUS COMPRISING: AN ELECTROMECHANICAL TRANSDUCER ELEMENT HAVING A HOLLOW GENERALLY-CYLINDRICAL SHAPE; A CONICAL REFLECTOR DISPOSED CONCENTRICALLY AND EXTERIORALLY OF SAID CYLINDRICAL ELEMENT; A SECOND CONICAL REFLECTOR DISPOSED CONCENTRICALLY AND INTERIRALY OF SAID CYLINDRICAL ELMENT, THE TWO CONICAL REFLECTORS BEING DISPOSED TO REFLECT WAVES IN ONE DIRECTION PARALLEL TO THE AXIS OF SAID CYLINDRICAL ELEMENT AND BEING EQUALLY SPACED FROM THE OPPOSED SURFACES OF SAID CYLINDRICAL ELEMENT SO THAT THE DISTANCES IN WAVE LENGTHS ALONG ANY RADIAL LINE TO CORRESPONDING INCREMENTAL AREAS ON THE CONICAL REFLECTOR SURFACES ARE SUBSTANTIALLY EQUAL; ONE OF SAID CONICAL REFLECTORS HAVING A RELATIVELY HARD AND NONCOMPLIANT SURFACE RADIALLY FACING SAID CYLINDRICAL ELEMENT AND THE OTHER OF SAID REFLECTORS HAVING A RELATIVELY SOFT AND COMPLIANT SURFACE RADIALLY FACING SAID CYLINDRICAL ELEMENT; SAID RELATIVELY HARD SURFACE HAVING AN ACOUSTIC IMPEDANCE SUFFICIENTLY HIGHER THAN ITS OPERATIVE AMBIENT ENVIRONS FOR SUBSTANTIALLY PRESERVING THE PHASE OF IMPINGING ACOUSTIC WAVES AND THE OTHER SURFACE HAVING AN ACOUSTIC IMPEDANCE SUFFICIENTLY LOWER THAN SAID ENVIRONS FOR SUBSTANTIALLY REVERSING THE PHASE OF IMPINGING WAVES.
US484134A 1965-08-31 1965-08-31 Broad band acoustic transducer Expired - Lifetime US3302163A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US484134A US3302163A (en) 1965-08-31 1965-08-31 Broad band acoustic transducer

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US484134A US3302163A (en) 1965-08-31 1965-08-31 Broad band acoustic transducer

Publications (1)

Publication Number Publication Date
US3302163A true US3302163A (en) 1967-01-31

Family

ID=23922896

Family Applications (1)

Application Number Title Priority Date Filing Date
US484134A Expired - Lifetime US3302163A (en) 1965-08-31 1965-08-31 Broad band acoustic transducer

Country Status (1)

Country Link
US (1) US3302163A (en)

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3375489A (en) * 1966-03-14 1968-03-26 Harry W. Kompanek Pressure compensated transducer
US3543059A (en) * 1968-10-28 1970-11-24 Us Navy Fluted cylinder for underwater transducer
US3618013A (en) * 1970-01-30 1971-11-02 Krupp Gmbh Transducer for determining the angle of incidence of sound waves
US3663841A (en) * 1970-04-22 1972-05-16 Electro Mechanical Design Ltd Ultrasonic transducers
US3703652A (en) * 1970-02-25 1972-11-21 Mitsubishi Electric Corp Electroacoustic transducer
US3755698A (en) * 1972-04-25 1973-08-28 Us Navy Free-flooded ring transducer with slow wave guide
FR2356126A1 (en) * 1976-05-12 1978-01-20 Sutures Inc CATHETER TRANSDUCER PROBE
DE2825396A1 (en) * 1977-06-10 1978-12-21 Thomson Csf REVERSIBLE ELECTROACOUSTIC CONVERTER ARRANGEMENT
US4237729A (en) * 1978-06-02 1980-12-09 Howmedica, Inc. Doppler flow meter
US4439847A (en) * 1981-12-21 1984-03-27 The Stoneleigh Trust High efficiency broadband directional sonar transducer
DE3241026A1 (en) * 1982-11-06 1984-05-10 Dornier System Gmbh SHOCK WAVE REFLECTOR
US4488271A (en) * 1983-06-20 1984-12-11 The United States Of America As Represented By The Secretary Of The Navy Deep ocean wide band acoustic baffle

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2005741A (en) * 1932-12-15 1935-06-25 Harvey C Hayes Magneto-strictive sound generator
US2746026A (en) * 1953-08-14 1956-05-15 Bendix Aviat Corp Half wave annular transducer
US3027964A (en) * 1958-06-24 1962-04-03 Ampex Loudspeaker

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2005741A (en) * 1932-12-15 1935-06-25 Harvey C Hayes Magneto-strictive sound generator
US2746026A (en) * 1953-08-14 1956-05-15 Bendix Aviat Corp Half wave annular transducer
US3027964A (en) * 1958-06-24 1962-04-03 Ampex Loudspeaker

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3375489A (en) * 1966-03-14 1968-03-26 Harry W. Kompanek Pressure compensated transducer
US3543059A (en) * 1968-10-28 1970-11-24 Us Navy Fluted cylinder for underwater transducer
US3618013A (en) * 1970-01-30 1971-11-02 Krupp Gmbh Transducer for determining the angle of incidence of sound waves
US3703652A (en) * 1970-02-25 1972-11-21 Mitsubishi Electric Corp Electroacoustic transducer
FR2161734A1 (en) * 1970-02-25 1973-07-13 Mitsubishi Electric Corp
US3663841A (en) * 1970-04-22 1972-05-16 Electro Mechanical Design Ltd Ultrasonic transducers
US3755698A (en) * 1972-04-25 1973-08-28 Us Navy Free-flooded ring transducer with slow wave guide
FR2356126A1 (en) * 1976-05-12 1978-01-20 Sutures Inc CATHETER TRANSDUCER PROBE
US4314098A (en) * 1977-06-10 1982-02-02 Thomson-Csf Reversible electroacoustic transducer device having a constant directivity characteristic over a wide frequency band
FR2394221A1 (en) * 1977-06-10 1979-01-05 Thomson Csf REVERSIBLE ELECTRO-ACOUSTIC TRANSDUCER DEVICE WITH CONSTANT DIRECTIVITY CHARACTERISTICS IN A WIDE FREQUENCY BAND
DE2825396A1 (en) * 1977-06-10 1978-12-21 Thomson Csf REVERSIBLE ELECTROACOUSTIC CONVERTER ARRANGEMENT
US4237729A (en) * 1978-06-02 1980-12-09 Howmedica, Inc. Doppler flow meter
US4439847A (en) * 1981-12-21 1984-03-27 The Stoneleigh Trust High efficiency broadband directional sonar transducer
DE3241026A1 (en) * 1982-11-06 1984-05-10 Dornier System Gmbh SHOCK WAVE REFLECTOR
EP0108190A2 (en) * 1982-11-06 1984-05-16 DORNIER SYSTEM GmbH Shock wave reflector
EP0108190A3 (en) * 1982-11-06 1984-07-25 Dornier System Gmbh Shock wave reflector
US4488271A (en) * 1983-06-20 1984-12-11 The United States Of America As Represented By The Secretary Of The Navy Deep ocean wide band acoustic baffle

Similar Documents

Publication Publication Date Title
US3360664A (en) Electromechanical apparatus
US3302163A (en) Broad band acoustic transducer
US3370187A (en) Electromechanical apparatus
US3198489A (en) Compound ultrasonic transducer and mounting means therefor
US3243768A (en) Integral directional electroacoustical transducer for simultaneous transmission and reception of sound
US4072871A (en) Electroacoustic transducer
KR100517059B1 (en) Transducer for underwater high-power use
US3510698A (en) Electroacoustical transducer
US2939970A (en) Spherical transducer
US3713086A (en) Hydrophone
US3287692A (en) Bender type electroacoustical apparatus
US3378814A (en) Directional transducer
US5726952A (en) Sound or ultrasound sensor
US4433399A (en) Ultrasonic transducers
US3460061A (en) Electroacoustic transducer with improved shock resistance
US3277436A (en) Hollow electro-acoustic transducer
US3094636A (en) Underwater transducer
US2746026A (en) Half wave annular transducer
US3525071A (en) Electroacoustic transducer
US3769532A (en) Mechanical decoupling device for attachment to electroacoustic transducers
US2961635A (en) Low-frequency underwater sound flexure mode ring drive transducer
US3546497A (en) Piezoelectric transducer element
US3215977A (en) Acoustic transducer
US3449712A (en) Folded transducer transmitting or receiving for low frequency underwater sound
US3972018A (en) Electromechanical transducer