GB2143105A

GB2143105A - A system for discriminating between a human voice signal and other sound signals

Info

Publication number: GB2143105A
Application number: GB08403418A
Authority: GB
Inventors: Akira Komatsu
Original assignee: Bodysonic KK
Current assignee: Bodysonic KK
Priority date: 1980-04-21
Filing date: 1984-02-09
Publication date: 1985-01-30
Also published as: GB2077078A; GB8403418D0; CA1184506A; IT1142404B; IT8148303A0; DE3115801A1; DE3115801C2; FR2480978B1; FR2480978A1; GB2143105B; GB2077078B

Abstract

A system for discriminating between a human voice signal and other sound signals has a low-pass filter 3 with a cut-off frequency of 150 Hz and a voltage-controlled amplifier 4 connected between its input terminal 1 and output terminal 2. A low-pass filter 5 having a cut-off frequency of 60 Hz, a rectifier circuit 5 and an integrator circuit 7 are connected between the input terminal 1 and the control terminal 4a of amplifier 4. In use, the amplifier 4 suppresses signals originating from a human voice but passes other low frequency signals. The output terminal 2 may be connected to a body felt vibration generator. <IMAGE>

Description

1 GB 2 143 105 A 1

SPECIFICATION A System for Discriminating between a Human Voice Signal and Other Sound Signals

This invention relates to a system for discriminating a human voice signal from other 70 sound signals.

In the living environment of human beings, various sounds exist. In recording and reproducing the sounds, it is required to record and reproduce them at high sensitivity and at high fidelity. In general, satisfying these requirements suffices.

In such general cases, all the sounds having entered, for example, a microphone have only to be equally amplified and reproduced. In some special uses, however, it becomes necessary to classify input signals depending on their properties or types and to subject a certain type of signals to processing different from those of the other types of signals.

For example, it may be desired to derive human voices from among other noises or to pick up the voice of an announcer separately from the other sounds such as music in case of recording sounds for a radio or television broadcast. It may also be desired to discriminate the human voice from other sounds when providing the input signal for a body felt vibration generator, such a generator having recently been proposed and put into practical use.

The body felt vibration generator is a device in '95 which, in order to recreate an original environment with sound reproducing equipment, signals having double bass sound components of e.g. below 1 50Hz forming amplifier output signal to be applied to loudspeakers (or headphones) are 100 converted into mechanical vibrations so as to directly give the latter to the human body as body-felt vibrations, and the sounds and the body-felt vibrations of the double bass sound region are simultaneously given to an appreciator, 105 thereby to provide an intense double bass sound feeling. The device is effective principally for the appreciation of music.

It has been experimentally confirmed that, when the device is combined with sounds other than music, for example, documentary sounds and effect sounds such as these which accompany an earth tremor or the feeling of a shock such as the roaring of a gun, the running sound of a street car or steam locomotive, noise emitted when a big tree is cut down, explosion, and the running sounds and engine sounds of an automobile, tractor etc., the impression of an original environment and dramatic effects which cannot be obtained with conventional sound reproducing equipment can be obtained.

When such device is incorporated into the cinema, television or the like, real presence and numerous dramatic effects will be obtained. In this regard, a film drama, a television drama or the 125 like is, in general, composed of the combination of human voices (conversation), music, and effect sounds.

Accordingly, when such sound signals are given to the appreciator in the form of the bodyfelt vibrations without performing any additional processing, good effects can be expected as to the sounds which accompany an earth tremor and the feeling of a shock, while body-felt vibrations are also produced for human voices (conversation). This latter effect has been experimentally revealed to cause a very unnatural feeling.

In order to produce good effects in film drama, the television drama or the like, therefore, the advent of a device which is responsive to the musical and effect sounds but it is not responsive to the human voices is desired.

In accordance with this invention, there is provided a system for discriminating between a human voice signal and other sound signals, said system comprising control means having an input terminal, an output terminal and a control terminal for controlling signals passing between said input and output terminals in accordance with a signal applied to said control terminal, and a double-bass sound region deriving circuit having a low-pass filter the cut-off frequency of which lies in the double-bass frequency region below the low frequency human voice range, an input terminal of said double- bass sound region deriving circuit being connected to the input terminal of said control means and the output terminal of said double-bass region deriving circuit being connected to the control terminal of said control means.

This invention will now be described in more detail by way of example with reference to the drawing in which:

Figure 1 is a block diagram of a system for discriminating human voice signals from other sound signals embodying this invention.

Hereunder, this invention will be illustratively described in conjunction with a body-felt vibration generator which is one example of application thereof. When the frequency components of human voices, music, effect sounds etc. are studied, the low region of the human voices (chiefly, male voices) extends to below 80Hz and the high region extends to about 1 OkHz in both the male and female voices though they are also dependent upon recording circumstances and individual differences.

The effect sounds are of a very large number of sorts, and have various frequency spectra. An earth tremor or such a sound as causing the feeling of a shock is characterized by including a - wide frequency distribution and abundament double-bass sound components. Musical sounds often have a frequency distribution which is uniform and wide compared with those of the other sounds.

In view of these facts, it might be possible to distinguish human voice sounds from other sounds by passing them through an appropriate filter. However, a low-pass filter which can remove the double bass sound fundamental wave component of human voices extending to below 8OHz needs to have its cut off frequency set to 2 GB 2 143 105 A 2 60Hz or below, which poses a problem. More specifically, among frequency components below approximately 1 5OHz which are effective as bodyfelt vibrations, the frequency component density is highest at spectra near 1 OOHz, and the distribution density at and below 50-60Hz is lower. Therefore, signals having been passed through the aforecited low-pass filter have most of the components effective for the body felt vibrations removed, and the effect of the body felt vibration generator is drastically spoilt.

Since the sound which accompanies an earth tremor includes double bass sound components of and below 60Hz sufficiently, it can give rise to the body felt vibrations. Without the components near 1 OOHz, however, the real feeling effect is lessened, and flat vibrations of unvivid feeling are caused. This situation may be likened to the sound of a loudspeaker from which a tweeter has been detached so that it cannot give forth highpitched sounds.

Figure 1 shows an example of a system which has eliminated such problem. Referring to the drawing numeral 1 designates an input terminal, which receives a sound signal from an amplifier. A first low-pass filter 3 having a cut off frequency of approximately 1 50Hz and a voltagecontrolled variable gain amplifier (VCA) 4 are connected between the input terminal 1 and an output terminal 2.

The low-pass filter 3 serves to derive from its input signal the double bass sound component below approximately 1 5OHz convenient for the body felt vibration and to supply the derived component to the body felt vibration generator. The voltage-controlled variable gain amplifier 4 is an amplifier whose gain increases or decreases upon application of a voltage to a control end 4a thereof. In the present example, an amplifier whose gain increases with an applied positive voltage is employed.

Further connected to the input terminal 1 is the input side of a second low-pass filter 5 having a cut off frequency of approximately 60Hz. The output side of the second low-pass filter 5 is connected to the control end 4a of the voltagecontrolled variable gain amplifier 4 through a rectifier circuit 6 as well as an integration circuit 7.

In this circuit, when an effect sound of the type 115 which accompanies an earth tremor including double bass sound components of and below 60Hz abundantly has entered the input terminal 1 as the input sound signal, both the two low-pass filters pass the double bass sound components of the signal. An output signal of the second lowpass filter 5 is rectified by the rectifier circuit 6, and is thereafter integrated by the integration circuit 7. An output voltage of the integration circuit 7 is applied to the control terminal 4a of the voltage-controlled variable gain amplifier 4, and increases the gain of this amplifier. Thus, the double bass sound component signal having passed through the first low-pass filter 3 is amplified greatly and is delivered to the output terminal 2. Accordingly, when the body-felt vibration generator is connected to the output terminal 2, an appreciator can obtain the bodyfelt vibration. Since the output signal includes frequency components near 1 OOHz, a real vibration effect can be afforded.

Now, there will be described a case where a human voice signal has entered as the input signal. Since the human voice signal scarcely includes the double bass sound components of and below 6OHz, any double bass sound component does not pass through the second low-pass filter 5, so that the output voltage of the integration circuit 7 diminishes. Therefore, the gain of the voltage-controlled variable gain amplifier 4 decreases, the signal having passed through the low-pass filter 3 is scarcely amplified, and the output signal at the output terminal 2 becomes zero or very small. Accordingly, the human voice hardly gives rise to a body-felt vibration.

The voltage-controlled variable gain amplifier 4 can be replaced with a voltage-controlled variable frequency filter (VCF). It can also be replaced with a gate in the form of an analog switch, or the like. Since however, the binary "on"--off" switching in this case gives rise to an unnatural feeling, the gentle and continuous "on"--off" control based on the analog increase and decrease by the voltage-controlled variable gain amplifier 4 is more favourable after all.

In the above description, the human voices have referred only to the cases of voiced phones. Since unvoiced phones (consonants produced without the vibrations of the vocal chords) have their spectra in a higher frequency band, they are removed by the low-pass filter 3 for deriving the body-felt vibration signal (having a cut off frequency of approximately 1 5OHz) and cause no problem.

Even in the cases of voiced phones, voices of high fundamental wave frequencies such as childrens voices, female voices and high-pitched voices given further in singing a song cause no problem for the same reason. It has been experimentally verified that the difference of the distinguishabilities based on different languages is scarcely noticable which is thought to owe to the same reason.

This application is divided from application no. 8112276.

Claims

1. A system for discriminating between a human voice signal and other sound signals, said system comprising control means having an input terminal, an output terminal and a control terminal for controlling signals passing between said input and output terminals in accordance with a signal applied to said control terminal, and a double-bass sound region deriving circuit having a low-pass filter the cut-off frequency of which lies in the double-bass frequency region below the low frequency human voice range, an input terminal of said double- bass sound region 3 GB 2 143 105 A 3 deriving circuit being connected to the input terminal of said control means and the output terminal of said double-bass region deriving circuit being connected to the control terminal of said control means.

2. A system as claimed in claim 1 in which the double-bass sound region deriving circuit comprises said low-pass filter and a rectifier circuit and an integrator circuit connected in series with the low pass filter.

3. A system as claimed in claim 1 or claim 2 in which the cut-off frequency of the low-pass filter 45 is approximately 60Hz.

4. A system as claimed in any one of claims 1 to 3, wherein said control means includes a voltage-controlled variable gain amplifier whose gain varies in accordunce with a voltage applied to its control terminal.

5. A system as claimed in any one of claims 1 to 3, wherein said control means includes a voltage-controlled variable frequency filter, the frequency characteristics of which are controlled in accordance with a voltage applied to its control 55 terminal.

6. A system as claimed in any one of claims 1 to 3, wherein said control means includes a gate which is constructed as an analog switch which turns "on" and "off" in a binary fashion in accordance with a voltage applied to its control terminal.

7 A system as claimed in any one of claims 1 to 6 wherein the control means includes a lowpass filter.

8. A system as claimed in claim 7, wherein the low-pass filter included in the control means has a cut off frequency of approximately 1 5OHz.

9. A system as claimed in any one of claims 1 to 8, combined with a body-felt vibration generator.

10. A system for discriminating between a human voice signal and other sound signals substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

New Claims or Amendments to Claims Filed on 21st June, 1984. Superseded Claim 1.

New or Amended Claim 1. A system for discriminating between a human voice signal and other sound signals, said system comprising control means having an input terminal, an output terminal and a control terminal for controlling signals passing between said input and output terminals in accordance with a signal applied to said control terminal, and a double-bass sound region deriving circuit having a low-pass filter the cut-off frequency of which lies in the double-bass frequency region below the lowest normal point of the human voice spectrum, an input terminal of said double-bass sound region deriving circuit being connected to the input terminal of said control means and the output terminal of said double-bass region deriving circuit being connected to the control terminal of said control means.

Printed in the United Kingdom for Her Majesty's Stationery Office, Demand No. 8818935, 111985. Contractor's Code No. 6378. Published by the Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.