Communicating or reproducing an audible sound

• US 8,000,609 B2
• Filed: 04/12/2006
• Issued: 08/16/2011
• Est. Priority Date: 04/14/2005
• Status: Active Grant

• Current Assignee: British Telecommunications PLC (BT Group PLC)
• Original Assignee: British Telecommunications PLC (BT Group PLC)
• Inventors: Sikora, Edmund S R, Healey, Peter
• Primary Examiner(s): SEDIGHIAN, REZA
• Application Number:
  US11/918,434
• Publication Number:
  US 20090103928A1
• Time in Patent Office: 1,952 Days
• Field of Search: 398/140, 398/188, 398/16, 398/13, 398/20, 398/28, 398/33, 398/141, 356/477, 356/478, 250/227.19, 250/227.27, 385/12
• US Class Current: 398/141
• CPC Class Codes: H04B 10/548 Phase or frequency modulation
• CPC Class Codes: H04R 23/008 using optical signals for detecting or generating sound

Abstract

The present invention relates to the communication or reproduction of sound, in particular audible sound. There is provided a method of communicating a sound, including the steps of: transmitting, onto an optical link, pairs of signal copies, the signal copies of a given pair having a time offset relative to one another; applying the audible sound to the optical link, such that the audible sound causes a phase modulation to the transmitted signal copies; receiving modulated signal copies previously transmitted onto the link; and, for received pairs of signal copies, causing one signal copy of a pair to mix with the other signal copy of that pair so as to produce a signal representative of the sound. The sound is an audible sound. It has been found that a delay of at least 75 micro seconds allows for a better reproduction of audio sounds, since these have a relatively low frequency content.

Claims

1. A method of optically communicating an audible sound along an optical link, the method comprising:

transmitting, onto the optical link, pairs of optical signal copies, the optical signal copies of a given pair having a time offset relative to one another of at least 75 microseconds;

phase modulating the transmitted optical signal copies on the optical link, the phase modulation being caused by audible sound waves propagating through air to impinge on a sensing portion of the optical link;

receiving reflected modulated optical signal copies previously transmitted onto the optical link; and

,

for received pairs of optical signal copies, causing one optical signal copy of a pair to mix with the other optical signal copy of that pair so as to produce a signal representative of a sensed audible sound.

2. A method as claimed in claim 1, wherein the offset is at least 100 micro seconds.

3. A method as claimed in claim 1, wherein the sound is a speech sound.

4. A method as claimed in claim 1, wherein the sound is communicated from a first sensing portion location at which the signal copies are modulated, to a second location where the signal copies are received, the two locations being at least 1 km to 10 km apart.

7. A method as claimed in claim 1, further comprising:

reproducing a sensed audible sound in the form of a sound signal from the representative signal.

5. A method as claimed in 1, wherein the temporal offset is achieved using interferometer means.

6. A method as claimed in claim 5, wherein the signal copies of a pair a temporally re-aligned using the interferometer means.

8. A microphone system for reproducing an audible sound, comprising:

an optical link for sensing the audible sound;

a transmission stage for transmitting, onto the optical link, pairs of optical signal copies such that the signal copies of a given pair have a time offset relative to one another of at least about 75 microseconds; and

,

a receiving stage for receiving reflected optical signals of the optical signal copies previously transmitted onto the link,

wherein;

the optical link is arranged such that audible sound waves propagating over air and impinging on a sensing portion of the optical link cause the optical signal copies to suffer a phase modulation; and

the receiving stage is arranged, for received reflected pairs of optical signal copies, to cause one optical signal copy of a pair to mix with the other optical signal copy of that pair so as to enable reproduction of a sensed audible sound in the form of a sound signal.

9. A microphone system as claimed in claim 8, wherein the transmission stage and the receiving stage are formed in common by an interferometer stage.