Passive acoustical filters incorporating inserts that reduce the speed of sound

• US 9,087,506 B1
• Filed: 01/21/2015
• Issued: 07/21/2015
• Est. Priority Date: 01/21/2014
• Status: Active Grant

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Doppler Labs, Inc.
• Inventors: Lanman, Richard Fritz, Palmborg, Nils Jacob, Kraft, Noah, Oswaks, Jonathan, Wiggins, Dan
• Primary Examiner(s): Kim, Paul S
• Application Number:
  US14/601,926
• Publication Number:
  US 20150206524A1
• Time in Patent Office: 181 Days
• Field of Search: 381/99, 381/94.1, 381/94.3, 381/72, 381/73.1, 381/321
• US Class Current: 1/1
• CPC Class Codes: A61F 11/08 internal, e.g. earplugs
• CPC Class Codes: A61F 11/085 including an inner channel
• CPC Class Codes: G10K 11/04 Acoustic filters ; Acoustic resonators
• CPC Class Codes: G10K 11/16 Methods or devices for protecting against, or for damping, noise or other acoustic waves in general G10K11/36 takes precedence
• CPC Class Codes: G10L 21/0208 Noise filtering
• CPC Class Codes: G10L 21/0232 Processing in the frequency domain
• CPC Class Codes: H03G 3/32 the control being dependent upon ambient noise level or sound level
• CPC Class Codes: H03G 5/165 Equalizers; Volume or gain control in limited frequency bands
• CPC Class Codes: H03G 9/025 frequency-dependent volume compression or expansion, e.g. multiple-band systems H03G9/10, H03G9/18 take precedence
• CPC Class Codes: H04R 1/1008 Earpieces of the supra-aural or circum-aural type
• CPC Class Codes: H04R 1/1016 Earpieces of the intra-aural type
• CPC Class Codes: H04R 1/1083 Reduction of ambient noise active noise reduction per se G10K11/175; protective devices for the ear, e.g. providing acoustic protection A61F11/06
• CPC Class Codes: H04R 1/22 for obtaining desired frequency characteristic only circuit for combining transducers having different responses H04R3/00; for hearing aids H04R25/407
• CPC Class Codes: H04R 3/04 for correcting frequency response

Abstract

There is disclosed a passive acoustical filter including a first filter element coupled between an ambient and an ear of a listener, at least a portion of the first filter element filled with a material in which a speed of sound is lower than a speed of sound in air.

Claims

1. A passive acoustical filter to be coupled between an ambient and an ear of a listener, comprising:

a double-stage low-pass filter comprising a first low-pass filter element in series with a second low-pass filter element, expansion chambers of the first low-pass filter element and the second low pass filter element filled with respective inserts made from a material in which a speed of sound is lower than a speed of sound in air.

2. The passive acoustical filter of claim 1, wherein the material in which the speed of sound is lower than the speed of sound in air is a reticulated material.

3. The passive acoustical filter of claim 2, wherein the reticulated material is selected from a plastic foam material, cotton fibers, bamboo fibers, and yarn.

4. The passive acoustical filter of claim 1, wherein the double-stage low-pass filter is coupled in parallel with a high-pass filter element.

5. A passive acoustical filter to be coupled between an ambient and an ear of a listener, comprising:

a high pass filter element; and

a low-pass filter element in parallel with the high-pass filter element, an expansion chamber of the low-pass filter element filled with an insert made from a material in which the speed of sound is lower than a speed of sound in air.

6. The passive acoustical filter of claim 5, wherein the material in which the speed of sound is lower than the speed of sound in air is a reticulated material.

7. The passive acoustical filter of claim 6, wherein the reticulated material is selected from a plastic foam material, cotton fibers, bamboo fibers, and yarn.

8. A passive acoustical filter comprising:

an earbud including a first opening to receive sound from an ambient and a second opening to output filtered sound to an ear of a listener; and

a low-pass filter element contained within the earbud and coupled between the first opening and the second opening, the low-pass filter element comprising an expansion chamber filled with an insert made from a material in which a speed of sound is lower than a speed of sound in air; and

a high-pass filter element contained within the earbud and coupled in parallel with the low-pass filter element,

wherein a cutoff frequency of the low-pass filter element is equal to or less than 200 Hz.

9. The passive acoustical filter of claim 8, wherein the material in which the speed of sound is lower than the speed of sound in air is a reticulated material.

10. The passive acoustical filter of claim 9, wherein the reticulated material is selected from a plastic foam material, cotton fibers, bamboo fibers, and yarn.

11. A passive acoustical filter, comprising:

an earbud having a first opening to receive sound from an ambient and a second opening to output filtered sound to an ear of a user; and

a double-stage low-pass filter contained within the earbud and coupled between the first opening and the second opening, the double-stage low-pass filter comprising a first-low-pass filter element in series with a second low-pass filter element, the first and second low-pass filter elements respectively comprising first and second expansion chambers filled with respective inserts made from a material in which the speed of sound is lower than the speed of sound in air,

wherein cutoff frequencies of both the first low-pass filter element and the second low pass filter element are equal to or less than 200 Hz.

12. The passive acoustical filter of claim 11, wherein the double-stage low-pass filter is coupled in parallel with a high-pass filter element.

13. The passive acoustical filter of claim 11, wherein the material in which the speed of sound is lower than the speed of sound in air is a reticulated material.

14. The passive acoustical filter of claim 13, wherein the reticulated material is selected from a plastic foam material, cotton fibers, bamboo fibers, and yarn.