Helium-speech communication

• US 4,342,104 A
• Filed: 10/30/1980
• Issued: 07/27/1982
• Est. Priority Date: 11/02/1979
• Status: Expired due to Term

• Current Assignee: University of Edinburgh
• Original Assignee: University of Edinburgh
• Inventors: Jack, Mervyn A.
• Primary Examiner(s): Farley, Richard A.
• Application Number:
  US06/202,300
• Time in Patent Office: 635 Days
• Field of Search: 367/132, 179/1 UW, 179/1 SH
• US Class Current: 367/132
• CPC Class Codes: G10L 21/00 Speech or voice signal processing techniques to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its quality or its intelligibility G10L19/00 takes precedence

Abstract

The invention relates to a novel helium-speech unscrambler which can be located at a diver'"'"'s location, and enables the helium-speech voiced by the diver to be subjected to waveform time expansion to reduce the bandwidth of the helium speech (e.g. to 2 to 3 KHZ) prior to transmitting the speech signals to a distant location on a carrier wave selected for optimum transmission through the water.

Claims

1. A method of through-water communication of helium speech in which the bandwidth of a leading part of each pitch period of a diver'"'"'s helium speech is reduced by waveform time expansion to provide a signal bandwidth acceptable for modulating a carrier wave of a frequency selected for optimum through-water transmission, the carrier wave being modulated and fed directly into the water to a listening station, the degree of waveform time expansion effected at the diver'"'"'s location being preset and the listening station including means to modify the time expansion of the received signal to optimise intelligibility of the received speech.

2. The method of claim 1 in which the bandwidth (f_h) of the helium-speech is reduced by a factor of 1/χ

in the unscrambling device at the diver'"'"'s location and increased by a factor of γ

at the listener'"'"'s location, γ

being not greater than χ and

being adjustable by the listener.

3. The method of claim 2, in which the bandwidth of the signal modulating the carrier wave fed into the water is in the range 2 to 3 KHZ and the bandwidth of the signal fed to the listener is adjustable in the range 3 to 4 KHZ.

5. A method as claimed in claim 1 or claim 4, in which the carrier frequency is not greater than 8 KHZ.

4. A method of through-water communication of helium-speech in which a leading part of each pitch period of a diver'"'"'s helium-speech is subjected to a waveform time expansion to reduce the signal bandwidth to a level acceptable for use with a carrier frequency selected for optimum transmission through the water, a carrier wave at the said carrier frequency is modulated with the reduced bandwidth signal, the modulated carrier wave is fed via a first transducer into the water, the modulated carrier wave is received by a second transducer at a distant location, the output from the second transducer is demodulated, the demodulated output is operated on to reduce the waveform time expansion applied at the transmitter and the so operated-on signal is fed to a sound generator in the vicinity of a listener, said reduction in waveform time expansion being controlled by said listener.

6. Apparatus for through-water transmission of helium-speech voiced by a diver comprising transmitting equipment for the diver comprising a microphone, an analogue speech unscrambling device to subject a leading part of each pitch period of the diver'"'"'s speech received from the microphone to waveform time expansion and thereby to reduce the bandwidth of the helium-speech signals, and means to transmit the reduced bandwidth signals to a listener location, the transmitting means comprising a through-water communications transmitter to receive the reduced bandwidth signals and a transducer to feed the output from the transmitter directly into the water to the listener location, and at the listener location a receiving transducer, a further analogue helium-speech unscrambling device of variable expansion ratio, which is adjustable by a listener at said listener location, and a sound generator, for said listener, receiving output signals from the said further unscrambling device.

7. Apparatus as claimed in claim 6 in which the diver'"'"'s speech unscrambling device is capable of effecting a fixed waveform time expansion in the range 2:

1 to 3;

1.

8. A method of transmitting a diver'"'"'s helium-speech to a remote listening station which comprises subjecting an initial portion of each pitch period of the helium speech to waveform time expansion to reduce the bandwidth of the helium-speech and transmitting the reduced bandwidth signals to the listening station via an electrical line connecting the diver to the listening station, and adjusting the time expansion at the listening station to optimize intelligibility.

9. Apparatus for transmission of helium-speech voiced by a diver to a remote listener location comprising transmitting equipment for the diver comprising a microphone, an analogue speech unscrambling device to subject a leading part of each pitch period of the diver'"'"'s speech received from the microphone to waveform time expansion and thereby to reduce the bandwidth of the helium-speech signals, and means to transmit the reduced bandwidth signals to a listener location, and at said listener location,

a further analogue helium-speech unscrambling device of variable expansion ratio, means to vary said expansion ratio, and a sound generator receiving output signals from the said further unscrambling device.