Method and device for the precise analog of the compression part of the frequency range of audio signals

 

Group of inventions relates to the field of instrumentation and is intended for use when transmitting the audio signals on channels, limiting the bandwidth of transmitted signals. The technical result consists in increasing the intelligibility of speech. From the input signal to produce blittable and non-blittable parts of the frequency range, respectively, the low pass filter and a bandpass filter, having one common edge strip. Then convert part transpondeur up the frequency band, so that after division of its instantaneous frequency of inAffairsonce the lower boundary of the frequency band of the converted part was equal to the boundary frequency. Then after a precise dividing its instantaneous frequency of the converted portion of the input signal is added to the untransformed part of the form the output signal. The device contains a low pass filter (1), bandpass filter (2), the adder instantaneous frequency (3), lo (4), the instantaneous frequency divider (5), the adder signals (6). 1 Il.

Group of inventions relates to the field of instrumentation and is intended for use when transmitting the audio signals on channels, by limiting what Rivoli speech, transmitted over analog narrowband channels, such as channel sound transmission 16-mm film print with photographic recording of sound on telephone channels, radio channels with amplitude modulation, etc.

There is a method that compresses a part of the frequency range of the sound signals, implemented in the device according to A. C. of the USSR № 714473.

The obstacles to achieve the desired technical result when using the known method, namely, the exact analogue of the compression parts of the frequency range of the sound signals is that to divide the values of the instantaneous frequencies of the audio signal that exceeds a frequency threshold of compression, you need:

- firstly, to highlight this modulating function in the form of a proportional voltage;

- secondly, a large-scale decrease in the required number of times the value of this voltage, which exceeds the threshold value compression;

- thirdly, to synthesize this processed instantaneous frequency of the desired signal.

The mere frequency demodulation leads to decreased immunity of the signal as the opposite of frequency modulation, which, as is known, allows a gain in noise immunity. Then e is the but at the receiver input [1]. In other words, the frequency-modulated signal is less distorted by noise in the transmission channel, than, for example, signals with amplitude modulation.

It is known [1] that the instantaneous frequency of the sum of signal and noise is almost equal to the instantaneous frequency of the oscillations, which is greater. In the intervals of sounds in the transmission channel, in addition to noise, no nothing. Therefore, at the output of the frequency demodulator, we get not only the instantaneous frequency of the signal. The output of the frequency demodulator of the instantaneous frequency of the signal and noise are changing each other with the repetition frequency of pauses, so as pauses are an integral part of the sound signals. In addition, by suppressing the weak signal stronger are distorted frequency signal transient, and it is not only the beginning and end of each sound, but sometimes the middle. This explains the noticeable distortions arising from the processed signals, and a noticeable decrease of the signal-to-noise ratio, which prevents the sound quality and increase the intelligibility of speech.

The closest way to the same destination to the claimed group of inventions the method according to the totality of symptoms is the way the patent of the Russian Federation No. 2130651.The obstacles to achieve the desired technical result when using the known method and device for its implementation adopted for the prototype, is that when dividing a known manner the instantaneous frequencies of the audio signals is not possible to compress only the necessary part of the frequency range of audio signals.

The invention consists in the following.

A single task, which directed the claimed group of inventions is to improve the sound quality wideband audio signals and, mainly, to increase the intelligibility of speech signals analog narrowband channels.

Conducted by the author studies [2, 3] showed the possibility of improving the sound quality of musical signals and improve the intelligibility of speech with analog compression part of the frequency range of the wideband audio signals transmitted over a narrow-band channels and reproduced without restoring the magnitude of the instantaneous frequency. The study helped identify dependencies syllable intelligibility R from the frequency threshold compression fPCand gear ratio of the frequency in the frequency region above the threshold for channel transmission

Unified technical result that can be obtained by carrying out of a group of inventions is the exact analog compression ToAffairsonce part of the frequency range of the sound signals without appreciable reduction of the signal-to-noise ratio.

Specified single technical result in the exercise of invention the object of the method is achieved in that the compression part of the frequency range of the sound signals is achieved by dividing the instantaneous frequency, as in the known method, but unlike the prototype blittable and non-blittable parts of the frequency band extracted from the input signal, respectively, the low pass filter and a bandpass filter, having one common edge frequency which is the frequency threshold compression; convert part transpondeur up the frequency band, so that after division of its instantaneous frequency in KAffairsonce the lower boundary of the frequency band of the converted part was equal to the frequency threshold of compression, then the above exact dividing its instantaneous frequency of the analog method inAffairsonce converted part of the input signal is added to the untransformed part of the form the output signal.

the result in the implementation of the invention is achieved by that known device for the precise analog dividing the instantaneous frequency is further provided with a low pass filter, bandpass filter, adder instantaneous frequency, the local oscillator and the adder signals, and inputs both filters are connected to the input device, the output of bandpass filter connected to the first input of the adder instantaneous frequency, a second input connected to the output of the local oscillator, the output of the adder instantaneous frequency through the mentioned exact analog divider instantaneous frequency signals To aAffairsonce connected to the first input of the adder signal, a second input connected to the output of the low pass filter, the output of the adder signal formed by the output device.

Conducted by the applicant's analysis of the prior art, including the search for patents and scientific and technical information sources, has allowed to establish that the applicant is not detected similar as for a method and device characterized by signs, identical to all the essential features of a method and device of the claimed group of inventions, and the determination of the number of identified unique prototype, as the most similar set of features, has allowed to define a set of essential.

Therefore, each object group claimed invention meets the requirement of "novelty" of the current legislation.

To verify compliance of the claimed invention to the requirement of inventive step by the applicant conducted an additional search of the known solutions with the purpose of revealing of signs consistent with characteristics, distinctive features of the prototype, the results of which showed that each of the objects of the invention is not necessary for the expert in the obvious way from the prior art because the prior art defined by the applicant, not the influence provided the essential features of the claimed invention transformations to achieve a technical result.

Therefore, the claimed invention meets the requirement of "inventive step" of the current legislation.

The drawing shows a structural diagram of the inventive device, where 1 is a low pass filter; 2 - band-pass filter; 3 - adder instantaneous frequency; 4 - accurate analog divider instantaneous frequency signals To aAffairstime; 6 - adder signals.

Information confirming the ability of the invention to provide the above technical result is peredachi 16-mm film print is optimal according to the criterion of maximizing speech intelligibility is the processing mode of the instantaneous frequency with a threshold of 4 kHz compression and transmission coefficient-frequency in the area above the threshold K=0,1 (KAffairs=10). We will show by example the mentioned processing mode, how does the proposed device that implements the claimed method.

The proposed device operates as follows.

We take as a mathematical model input

where S(t) is the envelope, that is, the modulating function, which determines at each moment of time the amplitude of the signal, x(t) is the current phase, which is equal to

Moreover, the current phase is a function of the instantaneous frequency(t), which determines the frequency properties of real audio signals.

Input signal (1) is separated by filters on the low-frequency part of

and the high-frequency part of

The low-frequency portion of the input signal is a filter of low frequency (1 in the drawing), the upper cutoff frequency which is equal to 4 kHz. The high-frequency part of the input signal is band-pass filter (2 in the drawing), the lower cutoff frequency which is equal to 4 kHz. The choice of boundary frequencies of the filters due to the fact that according to the claimed method, they must be equal to the frequency threshold of compression.

Vysokochastotnom instantaneous frequency (3 in the drawing), which implements the following well-known transformation:

where cosgt - oscillation generated by the oscillator (4 in the drawing). To implement the transformation (5) adder instantaneous frequency contains two Phaser, two multiplier and myCitadel signals.

Accurate analog divider instantaneous frequency signals To aAffairs=10 times (5 in the drawing) generates at its output jitter

The frequency of the local oscillator is determined in accordance with the formulation of the method as follows:

We will substitute the number of

where fg=36 kHz.

Oscillation (5) formed in the adder signals (6 in the drawing) with untransformed low-frequency part of the input signal (3), and the generated output signal.

Thus, the above data confirm that the implementation of the use of the claimed invention the following conditions:

the tool embodying the claimed invention in its implementation, is intended for use in industry, namely technology, telecommunications, sound recording on a moving carrier;

for the claimed invention in the form as it Oh the application or known before the priority date tools and methods.

Therefore, the claimed invention meets the requirement of "industrial applicability" under the current law.

Literature

1. Vinitsky, A. C. Modulated filters and witness the reception of FM. - M.: Soviet radio, 1969. - 548 S.

2. Uvarov C. K. Exact komandirovka frequency and dynamic range of audio signals. - SPb.: Spbgukit, 2002. - 326 S.

3. Uvarov C. K. Measurement of key characteristics of the instantaneous frequency of the signals. Dept. hands. No. CT - D. JIST PICTURE ARTS AND SCIENCES, 1988. - 15 S.

Appendix 1

(To request: Method and device for the precise analog of the compression parts of the frequency range of the sound signals)

The results of measurements of syllable intelligibility of speech signals in a non-linear processing of their instantaneous frequencies

In the research process [2] of the possibility of reducing the loss of information occurring during the transmission of wideband audio signals over a narrow-band channels, it was found that for each narrowband channel you can find this characteristic of the nonlinear processing of the instantaneous frequency of the signal at the input of the channel, which provides improved sound quality of the signals at the output of the channel without recovery scale frequency.

The nonlinear characteristic of the processing of the instantaneous frequency 6.gif">second - with a smaller angle of inclination. The frequency at which the intersection of the straight lines is called a frequency threshold of compression.

The influence of parameters of nonlinear frequency compressione on the sound quality of speech signals was investigated by measuring the intelligibility of speech. Figure P1.1 shows the measured dependence of syllable intelligibility of the signals passed through the channel with low-pass filters, which formed the frequency characteristics of the narrow-band transmission channels. The upper cutoff frequency of the accepted values: 2, 3, 4 and 6kHz. Each point on the graphs obtained by averaging measurement results of ten people 10 syllabic tables 5 tables spoken male voice and 5 tables - female voice. With confidence probability of 0.95 of the magnitude of absolute error of measurements did not exceed 5%. When the measurements have established the level of the speech signal 80 dBA, the level of the white noise of 60 dBA.

The family of curves in Fig.P1.1, a parameter which is a frequency threshold of compression, characterize the dependence of syllable intelligibility from the gear ratio of the frequency K. the Values of intelligibility uncompressed speech correspond to points for which K=1,0. Family crimpless. The setting of these families is the transmission coefficient of frequency. Installed dependencies are optimal. The change in the optimal values of the coefficient of transmission frequencies from the values of the upper boundary of the frequency bandwidth of the channel is depicted in Fig.P1.3. The optimal frequency threshold of compression is reduced from 5 kHz to 3 kHz linearly with the change of the upper cutoff frequency of 6 kHz to 2 kHz.

For each processing mode, the instantaneous frequency can be plot syllable intelligibility from the upper cutoff frequency. Figure P1.4 shows a family of such curves, the parameter is the frequency threshold of compression, for the gain of the frequency K=0,1. Here is shown the dependence of intelligibility uncompressed signals from the values of the upper cutoff frequency.

During subjective measurements [2] was found the effect of the apparent expansion of the bandwidth of the sound transmission in the perception of signals with non-linear processed instantaneous frequency. In this regard, the notion of the effective (apparent) band of transmitted frequencies, which was determined by the increase in the intelligibility of the frequency-compressed signal transmitted over the channel with the upper limit hour is you actual bandwidth of the channel and the parameters of nonlinear processing of the instantaneous frequency is shown in Fig.P1.5. For example, for photographic soundtrack 16-mm film with the value of the upper cutoff frequency (determined from the decay of the amplitude-frequency response at 3 dB) 4 kHz, the magnitude of the effective (apparent) band of transmitted frequencies turned out to be equal to 10 kHz when the frequency threshold is 4 kHz and the transmission coefficient of frequency K=0,1.

Established dependencies allow to conclude that the non-linear processing of the instantaneous frequency can be used to improve the intelligibility not only when writing fotoforum 16-mm film prints, but also for other narrowband channels.

Claims

1. How accurate analog compression parts of the frequency range of an audio signal in which the instantaneous frequency part of the frequency range signals accurately divide the analog method inAffairstime, characterized in that blittable and non-blittable parts of the frequency band extracted from the input signal, respectively, the low pass filter and a bandpass filter, having one common edge frequency which is the frequency threshold of compression, and then converted part transpondeur up the frequency band, so that after division of its instantaneous frequency in KAffairsAffairsonce converted part of the input signal is added to the untransformed part of the form the output signal.

2. Device for accurate analog compression parts of the frequency range of an audio signal containing the exact analog divider instantaneous frequency signals To aAffairstime, characterized in that it is provided with a low pass filter, bandpass filter, adder instantaneous frequency, the local oscillator and the adder signals, and inputs both filters are connected to the input device, the output of bandpass filter connected to the first input of the adder instantaneous frequency, a second input connected to the output of the local oscillator, the output of the adder instantaneous frequency through the mentioned exact analog divider instantaneous frequency signals To aAffairsonce connected to the first input of the adder signal, a second input connected to the output of the low pass filter, the output of the adder signal formed by the output device.

 

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