Open-air type earphone

• US 4,742,887 A
• Filed: 02/12/1987
• Issued: 05/10/1988
• Est. Priority Date: 02/28/1986
• Status: Expired due to Term

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Yamagishi, Makoto
• Primary Examiner(s): FULLER, BENJAMIN R
• Application Number:
  US07/013,939
• Time in Patent Office: 453 Days
• Field of Search: 181/130, 181/132, 181/160, 181/129, 381/68.6, 381/153, 381/154, 381/156, 381/159, 381/160, 381/169, 381/187, 381/205, 381/68, 381/69, 381/158
• US Class Current: 181/129
• CPC Class Codes: H04R 1/1016 Earpieces of the intra-aural type
• 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 1/2819 for loudspeaker transducers
• CPC Class Codes: H04R 1/2826 for loudspeaker transducers
• CPC Class Codes: H04R 1/2857 for loudspeaker transducers
• CPC Class Codes: H04R 1/2888 for loudspeaker transducers

Abstract

An earphone has a housing divided by a driver unit into front and back cavities with a sound generation opening at the front thereof, a duct extending from the back cavity of the housing and having a length substantially larger than its diameter, and a casing attached to the housing and communicating with the back cavity through a pipe having a length longer than its diameter, with the resonant frequency determined by the casing and pipe being made near to the resonant frequency determined by the equivalent mass of the vibration system, that is, the diaphragm and voice coil of the driver unit, and by the compliance of the back cavity, so that the lowest resonant frequency of the earphone can be lowered while the peak that would otherwise be formed in the frequency characteristic of the earphone by the resonance between the back cavity and mass of the vibration system can be supressed for improving the high frequency characteristic.

Claims

1. An open-air type earphone comprising:

a driver unit including means defining a magnetic circuit, and a diaphragm, and voice coil which form a vibration system;

a housing containing said driver unit and having a sound generation opening to the atmosphere in front of said driver unit, and at least another opening to the atmosphere from said housing behind said driver unit and which has acoustic resistance material extending thereacross;

an elongated duct extending from said housing behind said driver unit and communicating, at one end, with the interior of said housing and, at its other end, with the atmosphere to provide an equivalent mass which is in parallel with an acoustic resistance of said acoustic resistance material and which is effective for reducing the lowest resonance frequency of the earphone;

a casing attached to said housing behind said driver unit; and

means defining a pipe communicating, at its ends, with said housing and said casing, respectively, and having a diameter and a length longer than said diameter of the pipe, a resonant frequency of a resonant circuit constituted by an equivalent mass formed by said pipe and a compliance formed by said casing being selected to be near to a resonant frequency which is determined by a mass of said vibration system and a compliance of said housing in back of said driver unit as to suppress a relatively high frequency peak that would otherwise be formed in the frequency characteristic of the earphone by said reducing of the lowest resonance frequency of the earphone.

2. An open-air type earphone according to claim 1;

wherein said casing has an opening to the atmosphere, and said opening of the casing has acoustic resistance material extending thereacross.

3. An open-air type earphone according to claim 1;

wherein said casing defines a closed chamber communicating only with said housing through said pipe.

4. An open-air type earphone according to claim 1, wherein said magnetic circuit includes a plate extending across said housing and dividing the latter into a back cavity and a front cacity communicating with said second generation opening, a magnet and a yoke, said diaphragm extends across said housing in said front cavity and said plate of the driver unit has unobstructed holes therethrough for communicating said front and back cavities.