EP0131033A4 - Procede et dispositif de traitement de signaux vocaux. - Google Patents

Procede et dispositif de traitement de signaux vocaux.

Info

Publication number
EP0131033A4
EP0131033A4 EP19840900467 EP84900467A EP0131033A4 EP 0131033 A4 EP0131033 A4 EP 0131033A4 EP 19840900467 EP19840900467 EP 19840900467 EP 84900467 A EP84900467 A EP 84900467A EP 0131033 A4 EP0131033 A4 EP 0131033A4
Authority
EP
European Patent Office
Prior art keywords
amplitude
signals
measure
audio signals
time
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.)
Withdrawn
Application number
EP19840900467
Other languages
German (de)
English (en)
Other versions
EP0131033A1 (fr
Inventor
Larry Keith Henrickson
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.)
Individual
Original Assignee
Individual
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 Individual filed Critical Individual
Publication of EP0131033A1 publication Critical patent/EP0131033A1/fr
Publication of EP0131033A4 publication Critical patent/EP0131033A4/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G7/00—Volume compression or expansion in amplifiers
    • H03G7/002—Volume compression or expansion in amplifiers in untuned or low-frequency amplifiers, e.g. audio amplifiers
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G9/00—Combinations of two or more types of control, e.g. gain control and tone control
    • H03G9/02—Combinations of two or more types of control, e.g. gain control and tone control in untuned amplifiers
    • H03G9/025—Combinations of two or more types of control, e.g. gain control and tone control in untuned amplifiers frequency-dependent volume compression or expansion, e.g. multiple-band systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
    • H04R2225/00—Details of deaf aids covered by H04R25/00, not provided for in any of its subgroups
    • H04R2225/43—Signal processing in hearing aids to enhance the speech intelligibility
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
    • H04R25/00—Electric hearing aids
    • H04R25/35—Electric hearing aids using translation techniques
    • H04R25/356—Amplitude, e.g. amplitude shift or compression

Definitions

  • This invention relates generally to speech processing, and more particularly the invention relates to a method and means for amplifying speech, such as for the hard of hearing, without adversely affecting the signal intelligence thereof.
  • Speech compression systems are known which employ automatic gain control.
  • prior art systems employing peak clipping and instantaneous compression produce harmonic distortion which tends to emphasize the stronger, low-frequency components of speech and obscures the higher frequencies.
  • a comprehensive survey is presented by Braida et al in "Hearing Aids - A Review of Past Research on Linear Amplifica ⁇ tion, Amplitude Compression, and Frequency Lowering", American Speech-Language-Hearing Association, Rockville, Maryland, April 1979.
  • This survey provides an extensive critical review of the compression literature in conjunction with a tutorial on compression concepts. The survey suggests that the lack of benefits from compression as shown in the survey literature reflects more a failure of researchers to adequately grasp the concepts and complexity of compression, in theory and implementation, rather than the potential benefit of amplitude compression itself.
  • the acoustical patterns of speech can be syste ically analyzed in three primary time-domain components: (1) a fine-temporal pattern reflecting the spectral distribution of each brief acoustic segment, (2) a gross-temporal pattern reflect ⁇ ing the durations of the various acoustic segments based on changes in fine-temporal patterns, and (3) a time-varying amplitude pattern.
  • the fine temporal cues from segments of speech as short as- five or ten milliseconds will often provide a listener with suffi ⁇ cient information to identify the place of articulation for consonants.
  • the gross temporal pattern will often provide sufficient information regarding the manner of articulation, especially among the classes of fricatives, affricates and stop-plosives.
  • the time varying amplitude pattern, or "speech envelope" is the natural result of a speech production process but may convey mostly redundant information already conveyed by a gross-temporal pattern.
  • An object of the present invention is an improved method of processing speech to facilitate reception without distorting the intelligible content thereof.
  • Another object of the invention is apparatus for compressing speech patterns whereby the variations in time varying amplitude pattern or envelope are minimized without adversely affecting the fine-temporal and gross-temporal patterns of the speech.
  • the present invention is directed to a method and apparatus for processing speech in which a time- varying averaged or root-mean-square (RMS) amplitude pattern is obtained and used to normalize the time varying amplitude pattern of speech and provide a compressed speech pattern positioned between the speech awareness threshold and the uncomfortable loudness level, ideally at the listener's most comfort ⁇ able level.
  • Spectral shaping is employed to emphasize the high-frequency content.
  • the invention can be implemented in a single channel or multi-channel system. Suitable microphone means is employed to pick up a speech pattern, and the speech pattern from the microphone is prea plified and then processed by a suitable shaping filter which emphasizes the high frequency content thereof.
  • the amplitude of the spectrally shaped signal is then determined over a specific time period, and the inverse of the root-mean-square is then used to modulate the spectrally shaped signal, thus producing a normalized amplitude.
  • the shaped signal is delayed for a sufficient time period to compensate for the time delay involved in the root-mean-square determina ⁇ tion prior to the amplitude compression.
  • the resulting signal is thus compressed and then adjusted to the desired hearing range with the spectral shaping provid ⁇ ing a retention of the fine-temporal pattern and the gross-temporal pattern.
  • Figure 1 is a functional block diagram of a single channel speech processing apparatus in accordance with one embodiment of the present invention.
  • Figure 2 is a graph illustrating the compression of speech in accordance with the present invention.
  • FIG. 3 is a functional block diagram of a multi ⁇ channel embodiment of speech processing apparatus in accordance with the invention.
  • FIGS. 4A and 4B are functional block diagrams of a tape recording system in accordance with other embodi ⁇ ments of the invention.
  • Figure 1 is a functional block diagram of a single channel speech processor in accordance with one embodiment of the invention which has been built using conventional, commercially avail ⁇ able components.
  • a microphone 10 In this embodiment a microphone 10
  • Wi IPO having a broad frequency response picks up audio signals and transmits electrical signals to a pre-amplifier 12 having 26 dB of gain between 100 Hertz to 10K Hertz.
  • the amplified signal is then passed to high frequency emphasis circuity 14 (e.g. TI064 quad amplifier) which provides 6 dB/octave gain over the range from 100 Hertz to two kiloHertz and a flat response above two kiloHertz.
  • An auxiliary input is provided at 16 whereby signals from a radio receiver, for example, can be applied to the high frequency emphasis circuitry 14.
  • the signal from circuitry 14 is then passed to an RMS detector high-frequency emphasis circuitry 14 is also provided to delay circuitry 18 having a delay equal to the time constant of the RMS detector 16.
  • the RMS detector comprised an analog series AD 536A and the delay circuitry 18 comprised a Reticon SAD 4096 bucket brigade device operated from a 80 kilohertz digital clock 20.
  • the delayed signal from the delay device 18 is then applied as the numerator in a divider circuit 20 (e.g. Analog Devices AD 535 precision divider) and the RMS amplitude of the delayed signal is applied to the divider 20 as a denominator. Accordingly, the output from the divider 20 is a delayed amplitude compressed signal which is applied to the receiver 22 (Knowles ED 1925).
  • a divider circuit 20 e.g. Analog Devices AD 535 precision divider
  • the output from the divider 20 is a delayed amplitude compressed signal which is applied to the receiver 22 (Knowles ED 1925).
  • Figure 2 is a plot of the compressed output level in dB SPL for the signal applied to receiver 22 versus the input level in dB SPL of the signal from the microphone 10. For input levels below about 45 dB, the output level is attenuated. At an input level of 45 dB, the output level is compressed and maintained uniform at approximately 100 dB S JJ w ⁇ i ⁇ is ⁇ ne MCX * level. The compression ratio remains at 10:1 or greater for input levels above 45 dB.
  • Figure 3 is a multi-channel signal compression system in accordance with another embodiment of the invention in which signals are filtered and compressed in a plurality of frequency bands.
  • signals from the microphone 30 are applied to a low * band (100-400 hZ) filter 32, a middle band (400-1,600 Hz) filter 34, and a high band (l,.600-6,400Hz) filter 36.
  • Signals from each of the filters are passed to amplitude compressor circuitry 38, 40, and 42.
  • Each of the compressor circuits includes delay circuitry, RMS detector circuitry, and divider circuitry as illustrated in Figure 1. Because each channel includes a narrow band of frequencies, the high frequency emphasis circuitry of Figure 1 is not required.
  • the compressed signals are then applied to a summing amplifier 44 with the composite summed signal then applied to the receiver 46.
  • Figures 4A and 4B are functional block diagrams of other embodiments of the invention useful with tape recorders and in which the compressed signal and the detected RMS value are both recorded in time sequence with a tape recorder.
  • signals from the microphone 50 or other audio source are applied to amplitude compressor 52 which may be a single channel device as in Figure 1 or a multiple channel device as in Figure 3.
  • the compressed audio signal is then recorded in an analog channel of the tape recorder 54, and the detected RMS value is recorded in an FM channel of the recorder 54.
  • the recorded compressed audio signal and the recorded RMS value can be applied to a multiplier 56 from which the original audio signal and the original dynamic range is produced.
  • the resulting decompressed signal is applied through frequency de-emphasis circuit 58 to the receiver 59.
  • Figure 4B is a sampled digital recording system similar to the analog system of Figure 4A.
  • signals from microphone 60 are applied to the amplitude compressor 62, as in Figure 4A, and then the compressed audio signal and the RMS value are converted to digital form by analog to digital circuits 63 and 65.
  • the digital signals are then stored in digital recorder 64.
  • the recorded signals are converted back to analog signals by digital to analog converter 57 and multi ⁇ plying DAC 66.
  • the decompressed signals from DAC 66 are frequency de-emphasized at 68 and then applied to the receiver 69.
  • an RMS detector has been employed.
  • other measures of the signal amplitude over a period of time including an average value and an approximation of the RMS value, can be employed.
  • RMS value includes suitable approximations thereof.
  • a divider has been employed in the preferred embodiments for obtaining the compressed signal, a logarithmic measure of the detected RMS or averaged value can be employed for obtaining the compressed value.
  • the invention has broad applications including, for example, hearing aids and audio storage media (as described herein) , sampled digital storage system, broadcast systems, public address systems, and general voice communication including telephones.
  • the invention is especially useful for communication in a noisy environment and through a noisy communication link such as in field applications.

Landscapes

  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Tone Control, Compression And Expansion, Limiting Amplitude (AREA)
  • Telephonic Communication Services (AREA)
  • Electrotherapy Devices (AREA)
  • Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)

Abstract

Procédé et appareil de traitement de signaux audio permettant d'obtenir une mesure de l'amplitude des signaux audio au cours d'une période de temps sélectionnée. Les signaux audio (Fig. 1) pour la période de temps sélectionnée sont retardés (18) jusqu'à obtenir la mesure de l'amplitude (16), et ces mêmes signaux audio retardés sont ensuite normalisés (20) en utilisant la mesure d'amplitude. Une accentuation des fréquences élevées (14) peut être utilisée avant d'obtenir la mesure d'amplitude. D'une manière alternative, un système multi-canaux (Fig. 3) peut être utilisé pour le traitement des signaux audio dans des bandes de fréquence limitées (32, 34, 36). Le procédé et l'appareil peuvent être utilisés pour différentes applications, comprenant des prothèses auditives, des supports de stockage audio, des systèmes de transmission et de sonorisation extérieure, ainsi que des systèmes de communications vocales tels que des systèmes téléphoniques.
EP19840900467 1983-01-03 1983-12-23 Procede et dispositif de traitement de signaux vocaux. Withdrawn EP0131033A4 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US45525083A 1983-01-03 1983-01-03
US455250 1983-01-03

Publications (2)

Publication Number Publication Date
EP0131033A1 EP0131033A1 (fr) 1985-01-16
EP0131033A4 true EP0131033A4 (fr) 1985-07-01

Family

ID=23808037

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19840900467 Withdrawn EP0131033A4 (fr) 1983-01-03 1983-12-23 Procede et dispositif de traitement de signaux vocaux.

Country Status (7)

Country Link
EP (1) EP0131033A4 (fr)
JP (1) JPS60500472A (fr)
CA (1) CA1216525A (fr)
DK (1) DK421084A (fr)
FI (1) FI843388A0 (fr)
NO (1) NO843506L (fr)
WO (1) WO1984002793A1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT398669B (de) * 1991-11-13 1995-01-25 Viennatone Gmbh Verfahren zur verarbeitung von signalen
DK0887958T3 (da) 1997-06-23 2003-05-05 Liechti Ag Fremgangsmåde til komprimering af optagelser af omgivelseslyd, fremgangsmåde til detektering af programelementer deri, indretninger og computerprogram dertil
US7092877B2 (en) * 2001-07-31 2006-08-15 Turk & Turk Electric Gmbh Method for suppressing noise as well as a method for recognizing voice signals

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3509558A (en) * 1965-10-22 1970-04-28 Nasa Wide range data compression system
US4071695A (en) * 1976-08-12 1978-01-31 Bell Telephone Laboratories, Incorporated Speech signal amplitude equalizer
US4169219A (en) * 1977-03-30 1979-09-25 Beard Terry D Compander noise reduction method and apparatus

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4112254A (en) * 1977-10-17 1978-09-05 Dbx, Inc. Signal compander system
US4249042A (en) * 1979-08-06 1981-02-03 Orban Associates, Inc. Multiband cross-coupled compressor with overshoot protection circuit

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3509558A (en) * 1965-10-22 1970-04-28 Nasa Wide range data compression system
US4071695A (en) * 1976-08-12 1978-01-31 Bell Telephone Laboratories, Incorporated Speech signal amplitude equalizer
US4169219A (en) * 1977-03-30 1979-09-25 Beard Terry D Compander noise reduction method and apparatus

Also Published As

Publication number Publication date
WO1984002793A1 (fr) 1984-07-19
NO843506L (no) 1984-09-03
DK421084D0 (da) 1984-09-03
FI843388L (fi) 1984-08-28
DK421084A (da) 1984-09-03
FI843388A7 (fi) 1984-08-28
EP0131033A1 (fr) 1985-01-16
CA1216525A (fr) 1987-01-13
FI843388A0 (fi) 1984-08-28
JPS60500472A (ja) 1985-04-04

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