ACOUSTIC TRANSMISSION

• US 20120163128A1
• Filed: 09/06/2010
• Published: 06/28/2012
• Est. Priority Date: 09/04/2009
• Status: Active Grant

• Current Assignee: BAE Systems Plc
• Original Assignee: BAE Systems Plc
• Inventors: Bagshaw, John Martin, Kent, Lionel William John
• Granted Patent: US 9,191,125 B2
• Time in Patent Office: Days
• US Class Current: 367/135
• CPC Class Codes: G08C 23/02 using infrasonic, sonic or ultrasonic waves
• CPC Class Codes: H04B 11/00 Transmission systems employing sonic, ultrasonic or infrasonic waves

Abstract

In apparatus for the acoustic transmission of power or data through a solid barrier such as a ships hull, assembly of an acoustic transducer to the hull is facilitated by bonding it first to an intermediate element by a thin layer of bonding adhesive and then bonding the intermediate element to the barrier using a second bonding layer. Acoustic matching of the transducer to the intermediate element is achieved by the thin layer, and the mechanically more robust base of the intermediate element can be rubbed on the barrier surface to displace or abrade away any unwanted debris or imperfections which might otherwise prevent the achievement of a thin second bonding layer. This makes the mounting and bonding process more tolerant of imperfections in the barrier surface due to either surface defects or particulate contamination. The transmit and receive transducers may be positioned relative to each other so as to suppress or attenuate multiple-transit signals. Thus the intermediate element may be wedge shaped to aid suppression of triple-transit signals. Transmit and receive transducers may have different wedge angles.

Claims

1. An apparatus for the transmission of an acoustic signal through a solid rigid substrate comprising:

a first acoustic transducer for converting electrical signals into acoustic signals, the transducer being mounted on a first face of a solid rigid substrate to transmit the acoustic signals into the substrate;

a second acoustic transducer mounted on a second face of the substrate so as to receive acoustic signals emitted by the first acoustic transducer and to convert the acoustic signals into electrical signals;

and characterised in that at least one of the transducers is mounted on its respective face of the substrate via an intermediate element, the transducer being bonded by a first bonding layer to the element, and the element being bonded to the substrate by a second bonding layer.

2. The apparatus of claim 1 wherein the thickness of the second bonding layer is configured to enable the passage of acoustic signals of a predetermined frequency and/or bandwidth.

3. The apparatus of claim 1 wherein the thickness of the second bonding layer is configured to enable the passage of acoustic signals of a predetermined frequency and/or bandwidth,

and wherein the second bonding layer comprises spacers to define its thickness.

4. The apparatus of claim 1 wherein the intermediate element has a grooved or otherwise profiled surface to which the second bonding layer is attached, to accommodate debris present between the face of the substrate and the intermediate element during bonding thereof.

5. The apparatus of claim 1 wherein the intermediate element is of a material which has an acoustic impedance which is the same as or similar to that of the substrate.

6. The apparatus of claim 1 wherein the first and second transducers are configured respectively to convert and transmit and to receive and convert electrical power via the acoustic signals.

7. The apparatus of claim 1 wherein the first and second transducers are configured respectively to convert and transmit and to receive and convert electrical power via the acoustic signals

and wherein the thickness of the second bonding layer is such that at the nominal frequency of the acoustic signals, single transit signals and triple transit signals received by the second transducer are in phase.

8. (canceled)

14. (canceled)

15. A method of fitting an acoustic transducer to a solid barrier substrate comprising bonding an active transducer element to an intermediate element and then bonding the intermediate element to the substrate by means of a second bonding layer.

16. The method of claim 15 comprising monitoring a signal passing to or from the transducer whilst the intermediate element is being bonded to the substrate, as indicative of the thickness of the second bonding layer and/or the position and/or orientation of the transducer relative to the substrate.

17. The method of claim 15 comprising grinding the intermediate element against the substrate during the bonding thereof.

18. An apparatus for the transmission of an acoustic signal through a solid rigid substrate comprising:

a first acoustic transducer for converting electrical signals into acoustic signals, the transducer being mounted on a first face of a solid rigid substrate to transmit the acoustic signals into the substrate;

a second acoustic transducer mounted on a second face of the substrate so as to receive acoustic signals emitted by the first acoustic transducer and to convert the acoustic signals into electrical signals;

and characterised in that at least one of the transducers is mounted on its respective face of the substrate via an intermediate element, the transducer being bonded by a first bonding layer to the element, and the element being bonded to the substrate by a second bonding layer,

wherein the electrical signals are modulated with data, the first transducer being configured to transmit the data as data-modulated acoustic signals, the second transducer being configured to receive said signals.

9. The apparatus of claim 18 wherein the thickness of the second bonding layer is chosen so that at a nominal frequency of the data-modulated acoustic signals triple transmit signals in the substrate are substantially attenuated.

10. The apparatus of claim 18 wherein a said intermediate element is shaped so as to suppress resonant acoustic reflections between the transducer and the face of the substrate between which the said element is bonded.

11. The apparatus of claim 18 wherein the intermediate element is wedge-shaped.

12. The apparatus of claim 18 wherein respective boresights of the first and second transducers are substantially parallel to each other, and preferably are substantially coincident.

13. The apparatus of claim 18 wherein respective boresights of the transducers are not parallel to each other.

19. An acoustic transducer for use in an apparatus for the transmission of an acoustic signal through a solid rigid substrate comprising:

a first acoustic transducer for converting electrical signals into acoustic signals, the transducer being mounted on a first face of a solid rigid substrate to transmit the acoustic signals into the substrate;

a second acoustic transducer mounted on a second face of the substrate so as to receive acoustic signals emitted by the first acoustic transducer and to convert the acoustic signals into electrical signals;

and characterised in that at least one of the transducers is mounted on its respective face of the substrate via an intermediate element, the transducer being bonded by a first bonding layer to the element, and the element being bonded to the substrate by a second bonding layer.