Systems and methods for acoustic mode conversion

Patent metadata

Field	Value
Publication number	US-11600258-B2
Application number	US-202016827502-A
Country	US
Kind code	B2
Filing date	Mar 23, 2020
Priority date	May 18, 2017
Publication date	Mar 7, 2023
Grant date	Mar 7, 2023

Abstract

The present disclosure provides systems and methods associated with mode conversion for ultrasound and acoustic radiation devices. A method is disclosed for manufacturing a mode converting structure comprising a holographic metamaterial that, when positioned relative to an acoustic radiation device (AR), modifies an acoustic field profile of the AR device from an input mode to an output mode, the method including identifying a volumetric distribution of acoustic material properties within the mode converting structure to transform an input pressure field distribution of acoustic radiation in the input mode to an output field distribution of acoustic radiation that approximates the target radiation pattern in the output mode and manufacturing the mode converting structure using the identified volumetric distribution of acoustic material properties.

First claim

What is claimed is:

1. A method for manufacturing a mode converting structure comprising a holographic metamaterial that, when positioned relative to an acoustic radiation device (AR), modifies an acoustic field profile of the AR device from an input mode to an output mode, the method comprising:
identifying a target radiation pattern for the AR device for a finite frequency range;
identifying boundaries of a three-dimensional volume to enclose a mode converting structure relative to the AR device;
identifying an input pressure field distribution of acoustic radiation on a surface of the mode converting structure from the AR device;
identifying a volumetric distribution of acoustic material properties within the mode converting structure to transform the input pressure field distribution of acoustic radiation in an input mode to an output field distribution of acoustic radiation that approximates the target radiation pattern in an output mode; and
manufacturing the mode converting structure using the identified volumetric distribution of acoustic material properties.

2. The method of claim 1 , wherein identifying the volumetric distribution of acoustic material properties comprises identifying a volumetric distribution of material properties including components of linear elasticity tensor and dynamic density tensor in a selected coordinate system.

3. The method of claim 1 , wherein identifying the volumetric distribution of acoustic material properties comprises identifying an acoustic material property combination to modify an acoustic field profile to achieve a target far-field radiation pattern.

4. The method of claim 3 , wherein the acoustic material property combination includes a combination of components of linear elasticity tensor and dynamic density tensor.

5. The method of claim 1 , wherein the identifying the volumetric distribution of acoustic material properties comprises identifying an acoustic material property combination to modify an acoustic field profile to achieve a target near-field radiation pattern.

6. The method of claim 5 , wherein the acoustic material property combination includes a combination of components of linear elasticity tensor and dynamic density tensor.

7. The method of claim 1 , further comprising:
assigning each of a plurality of unique acoustic material properties to a corresponding subset of voxels.

8. The method of claim 7 , further comprising:
forming each voxel of the subset of voxels from a material having a unique bulk modulus, such that each of the voxels in the subset of voxels has a unique acoustic material property based on the unique bulk modulus of the material from which the voxel is formed.

9. The method of claim 7 , further comprising:
forming each voxel of the subset of voxels from a material having a unique elastic modulus, such that each of the voxels in the subset of voxels has a unique acoustic material property based on the unique elastic modulus of the material from which the voxel is formed.

10. The method of claim 7 , further comprising:
forming each voxel of the subset of voxels from a material having a unique density, such that each of the voxels in the subset of voxels has a unique acoustic material property based on the unique density of the material from which the voxel is formed.

11. The method of claim 7 , further comprising:
forming each voxel of the subset of voxels from a material having a unique acoustic characteristic, such that each of the voxels in the subset of voxels has a unique acoustic material property based on a unique acoustically-relevant quality of the material from which the voxel is formed.

12. The method of claim 11 , wherein the unique acoustic characteristic of the material comprises at least two of: a density of the material, an elastic modulus of the material, and a bulk modulus of the material.

13. The method of claim 11 , wherein the unique acoustic characteristic of the material comprises a combination of a density of the material, an elastic modulus of the material, and a bulk modulus of the material.

14. The method of claim 1 , wherein the volumetric distribution is approximately homogeneous in one spatial dimension in a coordinate system, such that the volumetric distribution of the mode converting structure is effectively two-dimensional.

15. The method of claim 14 , wherein the coordinate system is Cartesian, such that the volumetric distribution corresponds to a uniform extrusion of a planar two-dimensional distribution perpendicular to its plane.

16. The method of claim 14 , wherein the coordinate system is cylindrical, such that the volumetric distribution corresponds to a uniform rotation of a two-dimensional planar cross section around a selected axis of revolution.

17. The method of claim 1 , wherein the mode converting structure is configured to be positioned on an end of an acoustic transmission line of the AR device.

18. The method of claim 17 , wherein the mode converting structure is configured to convert from a first mode that is associated with an acoustic transmission along the acoustic transmission line to a second mode that is a free-space acoustic radiation mode.

19. The method of claim 17 , wherein the mode converting structure is configured to convert from a first mode that is associated with free-space acoustic radiation to a second mode for acoustic transmission along the acoustic transmission line of the AR device.

20. The method of claim 1 , wherein identifying the volumetric distribution of acoustic material properties comprises identifying a first subset of voxels to be formed from a first material having a first acoustic characteristic and a second subset of voxels to be formed from a second material having a second acoustic characteristic that is different from the first acoustic characteristic.

21. The method of claim 1 , wherein identifying the volumetric distribution of acoustic material properties comprises: identifying the volumetric distribution of acoustic material properties for standard ambient temperature pressure (SATP) as a first subset of voxels to be formed from a first, solid material having a first acoustic characteristic and a second subset of voxels to be formed from a second, liquid material having a second acoustic characteristic that is different from the first acoustic characteristic.

22. The method of claim 1 , wherein identifying the volumetric distribution of acoustic material properties comprises selecting a volumetric distribution of primary acoustic refractive indices that corresponds to a holographic solution.

23. The method of claim 1 , wherein the target radiation pattern is configured to narrow a far-field beamwidth of the main lobe of the AR device.

24. The method of claim 1 , wherein the target radiation pattern is configured to increase a directional gain of the AR device.

25. The method of claim 1 , wherein the target radiation pattern is configured for creating at least one deep minimum or null in a far-field directivity pattern.

26. The method of claim 1 , wherein the target radiation pattern configured for modifying a direction in which a null in a far-field would occur with a unmodified AR device.

27. The method of claim 1 , wherein the target radiation pattern is configured to decrease far-field sidelobes of the AR device.

28. The method of claim 1 , wherein the target radiation patte

Assignees

• Elwha Llc

Inventors

• Urzhumov Yaroslav A

Classifications

• H04R1/34 Primary

  by using a single transducer with sound reflecting, diffracting, directing or guiding means {(specially adapted for hearing aids H04R25/402)} · CPC title

• G10K11/341 Primary

  Circuits therefor · CPC title

• G03H3/00

  Holographic processes or apparatus using ultrasonic, sonic or infrasonic waves for obtaining holograms; Processes or apparatus for obtaining an optical image from them (G03H1/22 takes precedence) · CPC title

• G01S15/897

  using application of holographic techniques · CPC title

• G10K11/24 Primary

  for conducting sound through solid bodies, e.g. wires · CPC title