Communicating or reproducing an audible sound

• US 20090103928A1
• Filed: 04/12/2006
• Published: 04/23/2009
• 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
• Granted Patent: US 8,000,609 B2
• Time in Patent Office: Days
• US Class Current: 398/140
• 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 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, characterized in that the sound is an audible sound and in that the temporal offset is at least 75 micro seconds.

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 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 or 10 km apart.

5. A method as claimed in claim 1, wherein there is provided a fluid medium between a sound source and the optical link, such that sound waves travel through the fluid medium to reach the link.

6. A method as claimed in claim 5, wherein the fluid medium is a gaseous medium.

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

8. A method as claimed in claim 7, wherein the signal copies of a pair a temporally re-aligned using the interferometer means.

9. A microphone system for reproducing an audible sound, including:

an optical link for sensing the audible sound;

a transmission stage for transmitting, onto the optical link, pairs of signal copies such that the signal copies of a given pair have a time offset relative to one another, the optical link being arranged such that the sound causes the signal copies to suffer a phase modulation; and

,

a receiving stage for receiving modulated signal copies previously transmitted onto the link, the receiving stage being arranged, for received pairs, to cause one signal copy of a pair to mix with the other signal copy of that pair so as to reproduce the audible sound in the form of a sound signal, wherein the temporal offset is greater than 75 micro seconds.

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