Remotely installed transmitter and a hands-free two-way voice terminal device using same

• US 6,272,360 B1
• Filed: 07/03/1997
• Issued: 08/07/2001
• Est. Priority Date: 07/03/1997
• Status: Expired due to Fees

• Current Assignee: Pan Communications, Inc.
• Original Assignee: Pan Communications, Inc.
• Inventors: Yamaguchi, Noboru, Konomi, Masao
• Primary Examiner(s): Hudspeth, David R.
• Assistant Examiner(s): Lerner, Martin
• Application Number:
  US08/888,281
• Time in Patent Office: 1,496 Days
• Field of Search: 455/569, 455/570, 455/297, 381/71.4, 381/91, 381/94.7, 381/302, 381/361
• US Class Current: 455/569.2
• CPC Class Codes: H04M 1/19 Arrangements of transmitters, receivers, or complete sets to prevent eavesdropping, to attenuate local noise or to prevent undesired transmission; Mouthpieces or receivers specially adapted therefor circuit arrangements for preventing eavesdropping H04M1/68; telephone cabinets E04H1/14
• CPC Class Codes: H04M 1/20 Arrangements for preventing acoustic feed-back H04M1/62 takes precedence
• CPC Class Codes: H04M 1/6041 Portable telephones adapted for handsfree use
• CPC Class Codes: H04R 1/20 Arrangements for obtaining desired frequency or directional characteristics for stereophonic purpose H04R5/00

Abstract

A remotely installed transmitter capable of clearly picking up only the voice of a person who is talking despite being installed away from the speaker'"'"'s mouth and without causing feedback despite increased sensitivity, and a hands-free two-way voice terminal device using such a transmitter. In the remotely installed transmitter, a bidirectional microphone is installed at a central position of two pipes, two sound pick-up chambers are formed on both the right side and the left side of the pipes, the two sound pick-up chambers are stuffed with a sound-absorbing material, the shapes and sizes of the sound pick-up chambers are determined so that minimum voice resonance frequencies of the two sound pick-up chambers when they are not stuffed with the sound-absorbing material are both higher than the used upper-limit frequency of voice of the transmitter, and the amount of the sound-absorbing material is adjusted so that the voice frequency characteristics acquire monotonous attenuation characteristics in a voice frequency band higher than the used upper-limit frequency of voice.

Claims

1. A remotely installed transmitter comprising:

a bidirectional microphone installed at a central position in a pipe having a predetermined length;

a plurality of sound pick-up ports formed at suitable positions at least at the right and left ends of said pipe;

a plurality of sound pick-up chambers formed in said pipe, a first on the right side of said microphone and a second on the left side of said microphone;

sound-absorbing material situated within the plurality of sound pick-up chambers, wherein the shapes and sizes of said sound pick-up chambers are determined so that minimum voice resonance frequencies of said sound pick-up chambers when they are not stuffed with the sound-absorbing material are higher than the used upper-limit frequency of voice of the transmitter, and the amount of the sound-absorbing material is adjusted so that the frequency characteristics of the transmitter acquire monotonous attenuation characteristics in a frequency band higher than said used upper-limit frequency of voice.

2. The remotely installed transmitter according to claim 1, wherein the shapes and sizes of the sound pick-up chambers are determined so that minimum resonance frequencies of the sound pick-up chambers when they are not stuffed with the sound-absorbing material are higher than the used upper-limit frequency of voice of the transmitter, the amount of the sound-absorbing material being adjusted so that the sensitivities at minimum voice resonance frequencies of said sound pick-up chambers after being stuffed with the sound-absorbing material are not higher than twice the sensitivity at 1 KHz.

3. The remotely installed transmitter according to claim 1, wherein the minimum voice resonance frequencies of the sound pick-up chambers when they are not stuffed with the sound-absorbing material are higher than two-thirds the used upper limit frequency of the voice frequency band of the transmitter.

4. The remotely installed transmitter according to claim 1, wherein a length from the tip of said pipe to the central position of the microphone is selected to be not longer than ¼

, or longer than ⅛

but not longer than ¼

, of the wavelength of the used upper-limit frequency of voice of the transmitter.

5. The remotely installed transmitter according to one of claims 1 and 2, wherein an ambient noise suppressing circuit is connected to an output terminal of said microphone, the ambient noise suppressing circuit having amplification characteristics such that the amplification gain thereof increases with an increase in an output level of the microphone.

6. The remotely installed transmitter according to claim 5, wherein said ambient noise suppressing circuit comprises:

a gain controller for amplifying an output signal of said microphone;

a band-pass amplifier for passing signals of a particular frequency band only among the signals output from said microphone;

a peak detector for detecting a peak value of the signals that have passed through said and-pass amplifier; and

a holding circuit for holding the peak value output by said peak detector for a predetermined period of time to control the amplification gain of said gain controller depending upon said peak value that is held.

7. A hands-free two-way voice terminal device having a transmitter and a receiver, the transmitter being the remotely installed transmitter according to any one of claims 1 to 4, wherein said receiver is mounted on a first fixing portion is directed to an ear of a speaker, and said transmitter is mounted on a second fixing portion remote by a predetermined distance from the mouth of the speaker so that a tip of the pipe is directed toward the speaker.

8. The hands-free two-way voice terminal device according to claim 7, wherein said receiver and said transmitter are arranged within a vehicle.

9. The hands-free type two-way voice terminal device according to claim 8, wherein said receiver is mounted on a center pillar and said transmitter is mounted on a sun visor.

10. The hands-free type two-way voice terminal device according to claim 8, wherein said receiver is mounted on a first side surface of a headrest of a seat and said transmitter is mounted on a second side surface of the headrest.

11. The hands-free type two-way voice terminal device according to claim 8, wherein said receiver and said transmitter are mounted on a belt member detachably attached to a headrest of a seat, said receiver and said transmitter being located on opposite sides of the headrest.

12. The hands-free two-way voice terminal device according to claim 7, wherein said receiver and said transmitter are arranged within a portable computer.