AU2005324240B2

AU2005324240B2 - Electroacoustic converter

Info

Publication number: AU2005324240B2
Application number: AU2005324240A
Authority: AU
Inventors: Rainer Busch
Original assignee: Atlas Elektronik GmbH
Current assignee: Atlas Elektronik GmbH
Priority date: 2004-12-23
Filing date: 2005-12-02
Publication date: 2008-10-30
Anticipated expiration: 2025-12-02
Also published as: KR20070102468A; EP1829024B1; DE102004062128A1; EP1829024A1; AU2005324240A1; DE102004062128B8; DE102004062128B4; KR101052811B1; WO2006072300A1

Description

00 ELECTROACOUSTIC TRANSDUCER O Field of the Invention The invention relates to an electroacoustic transducer for underwater use.

Background of the Invention A known electroacoustic transducer arrangement for an Sunderwater antenna (DE 43 39 798 Al) has a plurality of I3 10 hydrophones which are arranged at equal intervals vertically one above each other on a mount and, in order to simplify installation of the underwater antenna with good reception characteristics, are embedded together with a reflector, which is arranged behind them in the sound incidence direction, in acoustically transparent hard encapsulation composed of an elastomer which can be processed using a casting method, preferably polyurethane.

The reflector is in the form of a spring/mass system comprising a mass and a spring which is soft for sound, with the mass being provided by a metal plate and the spring which is soft for sound being provided by a panel which is soft for sound and is arranged on the rear face (facing away from the hydrophones) of the metal plate, which is preferably composed of aluminum.

A known submarine with a boat body (DE 101 28 973 Cl) which has a pressure body and an outer skin is equipped with a device for detection of torpedoes emitting sound pulses, which device has a large number of hydrophones which receive omnidirectionally, are distributed in an undefined manner over the surface of the boat body, and are mounted directly on its outer skin. The hydrophones are connected to a signal processing unit, which determines the direction of the torpedo in order to detect the torpedo position from the delay time differences between the output signals from selected hydrophones. The 00 2 distance from the torpedo is determined by trigonometric o calculation using direction angles which have been o determined by various hydrophone groups which are preferably located a long distance apart from one another on the boat body.

Any discussion of documents, acts, materials, devices, i articles or the like which has been included in the n present specification is solely for the purpose of providing a context for the present invention. It is not Sto be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.

Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

Summary of the Invention Embodiments of the invention may provide an electroacoustic transducer having a hydrophone for flush installation in the outer skin of a boat body and which, after installation, has a flat phase profile, without any sudden phase changing, and thus the free-field characteristic of a hydrophone, within its frequency range.

According to an aspect of the invention, there is an electroacoustic transducer having a reflector and a hydrophone which is arranged at an axial distance from the reflector, is arranged in front of the reflector in the 00 3 sound incidence direction and is in the form of a ceramic O hollow sphere, said hydrophone being supported on the O reflector by means of a spacer, characterized in that a reflector ring, supported on the reflector separated from the hydrophone, is arranged in front of the reflector, said reflector ring concentrically arranged with the hydrophone, and having an inner ring surface at a radial distance from the hydrophone, and in that the spatial M arrangement of the hydrophone and the reflector ring is so carried out that the hydrophone is provided at a C- predeterminable distance from an end surface of the reflecLor ring which faces away from the reflector.

In embodiments of the invention, the electroacoustic transducer has the advantage that the provision of the reflector ring and its arrangement (matched to the hydrophone position) mean that the phase profile of the transducer is largely flat, and has neither any ripple caused by constructive interference nor any sudden phase changes initiated by destructive interference. So-called phase-based signal analysis of the transducer signals is thus possible, that is to say signal evaluation which is based on the synchronicity of the selected transducers, for example the algorithms for determination of the range and direction of a target, using at least three selected transducers. Furthermore, the transducer may provide the capability to shift the mid-frequency or main frequency of the transducer with the maximum reception sensitivity to low frequencies or to higher frequencies as required by variation of the separation of the hydrophone with respect to the front face of the reflector ring facing the sound incidence direction, without the phase profile losing its linearity. The transducer behaves in the same way as a hydrophone located in the free field over a broad frequency range, for example from 1 kHz to 100 kHz.

00 It According to one embodiment of the invention, the reflector is composed of a metal plate, preferably a brass O plate, and a hard foam panel, which is arranged in front of the metal plate in the sound incidence direction and rests on the metal plate. The reflector is used to achieve a desired front-to-back ratio, the so-called reflection factor, of the transducer, and to suppress interference sound that is incident on the mount side.

c, Brief Description of the Drawings SThe invention will be described in more detail in the following text with reference to one exemplary embodiment, which is illustrated in the drawing and in which: Figure 1 shows a longitudinal section through an electroacoustic transducer, and Figure 2 shows a graph of the reception sensitivity of the transducer as a function of the frequency, for various installation positions of the hydrophone in the transducer as shown in Figure i.

Detailed Description of the Preferred Embodiments The electroacoustic transducer for underwater use, as is illustrated in the form of a longitudinal section in Figure 1, has a reflector 11 and a hydrophone 12 which is formed by a hollow ceramic sphere, a so-called spherical ceramic, which is arranged at a distance in front of the reflector 11 in the sound incidence direction. The reflector 11 comprises a metal plate 13, in the exemplary embodiment a brass plate, on whose front face pointing in the sound incidence direction a hard foam panel 14 is fitted. The hydrophone 12 is fitted to a spacer composed of hard foam, which is supported on the hard foam panel 14 at the end remote from the hydrophone. The 00 C. reflector 11 acts as a spring/mass system, and is used to Sachieve a desired front-to-back ratio, the so-called O reflection factor, of the transducer, and to largely suppress interference sound which is generated in a mount holding the transducer.

A reflector ring 16 which is concentric with respect to the hydrophone 12 is arranged in front of the reflector 11, and its inner ring surface 161, which surrounds an annular space 163, is at a radial distance from the hydrophone 12. In this case, the reflector ring 16 and the hydrophone 12 are spatially associated such that the hydrophone 12 is at a predetermined distance h from that end surface 162 of the reflector ring 16 which faces away from the reflector 11 and faces the sound incidence direction. If the distance h is positive, then the hydrophone 12 projects at least partially beyond the end surface 162, while if the distance h is negative, then the hydrophone 12 is at least partially recessed behind the end surface 162. In this case, the reflector ring 16 is supported on the hard foam panel 14 of the reflector 11 via one or more spacers 17 composed of hard foam. In the exemplary embodiment shown in Figure 1, the hydrophone 12 partially projects beyond the front end surface 162 of the reflector ring 16, with the distance h indicating the distance between the foremost point in the sound incidence direction on the sphere surface and the end surface 162.

In this installation position, the transducer has a reception sensitivity G, as is illustrated schematically by the curve a in the graph in Figure 2, over its frequency range from, for example, 1 kHz to 100 kHz. The maximum reception sensitivity of the transducer is at the main frequency or mid-frequency f*.

The sensitivity maximum of the transducer can be shifted to higher or lower frequencies by variation of the 00 6 installation position of the hydrophone 12, as is done o mainly by variation of the height of the spacer 15. If the O distance h is increased, then the maximum of the reception sensitivity is shifted towards lower frequencies, as is indicated by the arrow +h in Figure 2. The reception sensitivity of the transducer as a function of the 3 frequency then has a profile, for example, as shown by the curve b in Figure 2. The hydrophone 12 can also be Srecessed behind the front end surface 162 of the reflector In ring 16 by shortening the height of the spacer 15, in which case the distance h assumes negative values. In this case, the maximum reception sensitivity of the transducer is shifted towards higher frequencies, as is indicated by the arrow -h in Figure 2. If the hydrophone 12 is located entirely in the inner annular space 163 on the reflector ring 16 and it is recessed by a specific amount -h behind the front end surface 162 of the reflector ring 16, then the transducer has a reception sensitivity as a function of frequency as is illustrated by way of example by the curve c in Figure 2. The thickness of the reflector ring 16 is matched to the frequency band of the transducer, so that the linearity of the reception sensitivity is maintained, that is to say the reflector ring 16 acts like a virtually ideal reflector over the entire frequency band.

The hydrophone 12 is connected in a known manner via electrical connecting conductors 18, which are passed centrally through the spacer 15, through the hard foam panel 14 and through the metal plate 13, to an electronics device 19, which itself can be made contact with via a plug 20 which is only indicated in Figure 1.

All of the components of the electroacoustic transducer described above are enclosed in an encapsulation 21 composed of sound-transparent plastic. An elastomer which

I

00 C- can be processed using the casting method, preferably polyurethane, is used as the plastic. Attachment means 22 O are provided in the encapsulation 21, in order to attach the electroacoustic transducer to a mount. Attachment means 22 such as these are, for example, through-channels formed in the encapsulation 21, through which mounting bolts can be passed.

C<N

SThe electroacoustic transducer described above is designed in particular for fitting to the boat body of a submarine, with the transducer, to be more precise the front face of the encapsulation 21 pointing in the sound incidence direction, being inserted into the outer skin of the submarine body such that it is flush with the outer skin, and being attached to the pressure body of the submarine body. The outer skin of the boat body is indicated by 23 in Figure 1.

Claims

2. The transducer as claimed in claim 1, characterized in that the hydrophone projects at least partially beyond the end surface of the reflector ring.
3. The transducer as claimed in claim 1, characterized in that the hydrophone is at least partially recessed behind the end surface of the reflector ring.
4. The transducer as claimed in any one of the previous claims, characterized in that the spacer is made from hard foam. The transducer as claimed in any one of the previous claims, characterized in that the reflector ring is supported on the reflector via at least one further spacer composed of hard foam. 00
6. The transducer as claimed in any one of the previous claims, characterized in that the thickness of the O reflector is matched to the frequency range covered by the hydrophone.
7. The transducer as claimed in any one of the previous claims, characterized in that the reflector ring is composed of hard foam. I 10 8. The transducer as claimed in any one of the previous Sclaims, characterized in that the reflector comprises a metal plate and a hard foam panel, which covers a front face of the metal plate and faces the sound incidence direction.
9. The transducer as claimed in any one of the previous claims, characterized in that the reflector, the reflector ring, the spacer and the hydrophone are enclosed in an encapsulation composed of sound-transparent plastic, in particular of an elastic elastomer which is capable of being processed using a casting method, and in that attachment means for attachment of the transducer is cast in the encapsulation.
10. The transducer as claimed in claim 9, characterized by the transducer being fitted to a boat body, which has a pressure body and an outer skin, of a submarine in such a way that a front face of the encapsulation, which faces the sound incidence direction, is flush with the outer skin of the boat body.
11. An electroacoustic transducer having a reflector and a hydrophone which is arranged at an axial distance from the reflector substantially as hereinbefore described with reference to the accompanying drawings.