GB1386671A - Reception techniques for intelligibility of an audio frequency signal - Google Patents

Reception techniques for intelligibility of an audio frequency signal

Info

Publication number
GB1386671A
GB1386671A GB4972A GB4972A GB1386671A GB 1386671 A GB1386671 A GB 1386671A GB 4972 A GB4972 A GB 4972A GB 4972 A GB4972 A GB 4972A GB 1386671 A GB1386671 A GB 1386671A
Authority
GB
United Kingdom
Prior art keywords
speech
signal
interference
control signal
original
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
GB4972A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
CUNARD STEAM SHIP
Original Assignee
CUNARD STEAM SHIP
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by CUNARD STEAM SHIP filed Critical CUNARD STEAM SHIP
Priority to GB4972A priority Critical patent/GB1386671A/en
Priority to SE1678772A priority patent/SE398426B/en
Priority to NO482572A priority patent/NO138821C/en
Priority to US05/557,240 priority patent/US4044205A/en
Publication of GB1386671A publication Critical patent/GB1386671A/en
Expired legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers
    • H03G3/20—Automatic control
    • H03G3/30—Automatic control in amplifiers having semiconductor devices
    • H03G3/34—Muting amplifier when no signal is present or when only weak signals are present, or caused by the presence of noise signals, e.g. squelch systems
    • H03G3/345—Muting during a short period of time when noise pulses are detected, i.e. blanking
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G11/00—Limiting amplitude; Limiting rate of change of amplitude ; Clipping in general
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers
    • H03G3/20—Automatic control
    • H03G3/30—Automatic control in amplifiers having semiconductor devices
    • H03G3/34—Muting amplifier when no signal is present or when only weak signals are present, or caused by the presence of noise signals, e.g. squelch systems
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers
    • H03G3/20—Automatic control
    • H03G3/30—Automatic control in amplifiers having semiconductor devices
    • H03G3/34—Muting amplifier when no signal is present or when only weak signals are present, or caused by the presence of noise signals, e.g. squelch systems
    • H03G3/342—Muting when some special characteristic of the signal is sensed which distinguishes it from noise, e.g. using speech detector
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G7/00—Volume compression or expansion in amplifiers

Landscapes

  • Noise Elimination (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

1386671 Improving intelligibility of speech signals CUNARD STEAM-SHIP CO Ltd 18 Dec 1972 [3 Jan 1972] 49/72 Heading H4R Intelligibility of a speech signal containing interference is improved by selecting and filtering out 11 a narrow section of the signal in which interference is least and deriving a control signal Vc from the mean amplitude of the section to amplitude modulate 1-3 the interference. The interference frequencies are effectively confined to the original speech syllable envelope and are subjectively less disturbing. The incoming speech signal Oi passes to a compressor 1 whose gain is decreased in response to increase in the control signal V c whose amplitude equals the syllable amplitude. The output is a signal whose speech content is at constant level with the interference components in the same ratio to the speech as in the original waveform. This signal is limited 2 at the speech level and expanded 3 in reciprocal relationship to the compressor also in response to the control signal Vc. The output Oo is the original speech waveform with the leading and trailing edges of syllables slightly distorted and the noise frequencies within the original enelope. The control signal Vc is the amplified 12 output of a 200 Hz bandwidth filter turnable between 300 and 3000 Hz and receiving the input signal Oi after adjustment to a constant level by amplifier 10 gain-controlled by feedback 14. Impulse noises of short duration are detected 15, 16 to inhibit the control signal. The limiter 2 preferably includes a balanced modulator (17, Fig. 3, not shown), limiter, filter and heterodyne demodulator to produce a limited output free of harmonics. In a refinement (Fig. 4, not shown) the compression and limiting is performed in an infinite compressor (22) controlled by the speech-plusinterference, impulse noise is detected at the input to the circuit to inhibit a gate (35) for the signals Oi and a further a.g.c. precedes the whole circuit. Intersyllabic "white" noise may be removed by a circuit (Fig. 5, not shown) in which the outputs of respective short (30) and long (31) attack time constant paths are compared (32) to inhibit a gate (26) normally passing the control signals Vc.
GB4972A 1972-01-03 1972-01-03 Reception techniques for intelligibility of an audio frequency signal Expired GB1386671A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
GB4972A GB1386671A (en) 1972-01-03 1972-01-03 Reception techniques for intelligibility of an audio frequency signal
SE1678772A SE398426B (en) 1972-01-03 1972-12-21 METHOD AND DEVICE FOR IMPROVING PERCEPTION IN A LOW-FREQUENCY SIGNAL
NO482572A NO138821C (en) 1972-01-03 1972-12-29 PROCEDURES AND APPARATUS FOR A BETTER UNDERSTANDING OF A SOUND FREQUENCY SIGNAL CONTAINING INTERFERENCE AND DESIRED SPEECH SIGNALS
US05/557,240 US4044205A (en) 1972-01-03 1975-03-11 Reception techniques for improving intelligibility of an audio frequency signal

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB4972A GB1386671A (en) 1972-01-03 1972-01-03 Reception techniques for intelligibility of an audio frequency signal

Publications (1)

Publication Number Publication Date
GB1386671A true GB1386671A (en) 1975-03-12

Family

ID=9697488

Family Applications (1)

Application Number Title Priority Date Filing Date
GB4972A Expired GB1386671A (en) 1972-01-03 1972-01-03 Reception techniques for intelligibility of an audio frequency signal

Country Status (3)

Country Link
GB (1) GB1386671A (en)
NO (1) NO138821C (en)
SE (1) SE398426B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100464498C (en) * 2006-11-29 2009-02-25 北京中星微电子有限公司 A method and device for implementing adjustment of volume based on environmental noise detection

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100464498C (en) * 2006-11-29 2009-02-25 北京中星微电子有限公司 A method and device for implementing adjustment of volume based on environmental noise detection

Also Published As

Publication number Publication date
NO138821C (en) 1978-11-15
SE398426B (en) 1977-12-19
NO138821B (en) 1978-08-07

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Legal Events

Date Code Title Description
PS Patent sealed
PLE Entries relating assignments, transmissions, licences in the register of patents
PCNP Patent ceased through non-payment of renewal fee