RU2106074C1 - Spatial sound-reproducing system - Google Patents

Abstract

FIELD: radio engineering, design of monophonic and stereophonic sound recording and play back equipment used by individual User under conditions of specially unadopted room. SUBSTANCE: system incorporates signal source, device regulating amplitude-frequency characteristic, low-frequency amplifier, loudspeaker coupled in series and volume control, probing device, device automatically controlling amplitude-frequency characteristic, communication line. Output of probing device is connected with the aid of communication line to first input of device automatically controlling amplitude-frequency characteristic. Probing device is installed in listening point. Second input of device automatically controlling amplitude-frequency characteristic is coupled to output of signal source through device regulating amplitude-frequency characteristic. Output of device automatically controlling amplitude-frequency characteristic is connected to input of low-frequency amplifier. Probing device and communication line have capability to control gain factor and volume level in listening point. EFFECT: increased operational characteristics. 7 cl, 2 dwg

Description

 The invention relates to radio engineering and can be used in systems of monophonic or stereo sounding of premises of various sizes.

 Known spatial sound reproducing system containing a signal source, a device for regulating amplitude-frequency characteristics (AFC), a low-frequency amplifier and a loudspeaker connected in series, as well as a control attenuator and a sounding device (US patent N 4309570, CL H 04 S 1/00, published. 05.01.82).

 This system allows you to adjust the amplitude-frequency characteristic of the signal at the listening point directly by the listener, but does not allow you to accurately adjust the volume and amplitude-frequency characteristics depending on changes in the shape and volume of the room, the location of the speaker and the position of the listener. The system does not allow increasing the signal-to-noise ratio (noise) for the listening point.

 A spatial sound reproducing system is known, comprising a signal source, an amplitude-frequency response control device, a low-frequency amplifier, a loudspeaker connected in series, and a volume control, a sounding device, an automatic amplitude-frequency response control device, a communication line, while the output of the sounding device, by the communication line is connected to the first input of the device for automatic regulation of the amplitude-frequency characteristics, and the probe de- vice is installed at the listening point (SU, patent N 2,038,704, cl. H 04 R 3/04, publish. 06.27.95).

 This system allows you to automatically adjust the amplitude-frequency characteristics of the signal for an individual listener, taking into account changes in the shape and volume of the room, and adjust the volume of sound playback depending on the position of the listener in the room.

 Disadvantages: the signal source should not have normalized output characteristics; the system has a complex inertial scheme for adjusting the volume of sound reproduction and does not allow you to adjust the amplitude-frequency characteristic of the signal, taking into account the characteristics of the auditory perception of the listener; the system does not allow correction of the amplitude-frequency characteristics, filtering of noise and noise of the signal source, as well as volume correction directly from the listening point.

 The problem solved by the invention, improving the quality of sound reproduction for an individual listener, taking into account changes in the shape, volume of acoustic properties of the room, location of the speaker, location of the listening point, imperfection of the signal source, features of auditory perception of sound pressure frequencies, noise and noise, imperfection of the amplitude-frequency characteristics of the amplifier low frequency and loudspeaker.

 The technical result that can be obtained by carrying out the invention is to simplify the construction of volume control, compensate for the frequency distortion of the signal, increase the signal-to-noise ratio (noise) at the listening point.

 An additional technical result that can be obtained by implementing an embodiment of the invention is remote volume control directly from the listening point.

 To solve the problem with achieving a technical result in a well-known spatial sound reproducing system containing a signal source, an amplitude-frequency response control device, a low-frequency amplifier, a loudspeaker connected in series, and a volume control, sounding device, an automatic control of the amplitude-frequency response, line communication, while the output of the probing device via a communication line is connected to the first input of the device av aromatic regulation of the amplitude-frequency characteristics, and the probe device is installed at the listening point, according to the invention, the second input of the device for automatically regulating the amplitude-frequency characteristics is connected to the output of the signal source through the device for regulating the amplitude-frequency characteristics, the output of the device for automatically regulating the amplitude-frequency characteristics is connected to the input low frequency amplifier, and the probing device or communication line is configured to adjust the gain to control the volume level at the listening position.

 The device for regulating the amplitude-frequency characteristics can be made in the form of a tone control.

 The device for regulating the amplitude-frequency characteristics can be made in the form of a multi-band equalizer.

 The transmission coefficient of the probing device or communication line can be adjusted evenly for sound frequencies.

 The transmission coefficient of the probing device or communication line can be adjusted unevenly for sound reproduction frequencies.

 The device for regulating the amplitude-frequency characteristics can be configured to automatically control the level of the output signal.

 In an embodiment, the probing device can be made in the form of a microphone, volume control, radio transmitting device equipped with a transmitting antenna, which are connected in series, communication lines in the form of a radio receiving device with a receiving antenna, the output of which is the output of the communication line and connected to the first input of the automatic control device amplitude-frequency characteristics.

 Due to the introduction of new functional relationships between the blocks of the spatial sound reproducing system, it is possible to solve the problem with the achievement of the specified technical result.

 In FIG. 1 shows a functional diagram of a spatial sound reproducing system; in FIG. 2 is one of the options for a spatial sound reproducing system.

 The spatial sound reproducing system (Fig. 1) comprises a signal source 1, an amplitude-frequency response control device 2, a low-frequency amplifier 3, a loudspeaker 4 connected in series, and a volume control 5, a sounding device 6, an automatic amplitude-frequency response control device 7, a communication line 8, while the output of the probing device 6 through a communication line 8 is connected to the first input of the device 7 for automatically controlling the amplitude-frequency characteristics, and sounding device 6 is installed at the point of listening.

 The second input of the device 7 for automatically adjusting the amplitude-frequency characteristic is connected with the output of the signal source through the device 2 for regulating the amplitude-frequency characteristics, the output of the device 7 for automatically regulating the amplitude-frequency characteristics is connected to the input of the amplifier 3 of a low frequency, and the probing device 6 or communication lines 8 are made with the ability to adjust the transmission coefficient to control the volume level at the listening point.

 The receiving element of the probing device 6 can be made in the form of one or more microphones located in the immediate vicinity of the listener's head. There are various design options for the implementation of the sounding device 6, for example, in the form of a headgear, headphones, glasses, hairpins, clothespins, or the receiving element of the sounding device 6 can be mounted in a remote control of the operation of the spatial sound reproducing system.

 The greatest reliability of sound reproduction can be obtained with the location of the receiving element of the sounding device 6 near the hearing organs of the consumer.

 In FIG. 1 shows a variant of a system in which the volume control 5 and the sounding device 6 are structurally combined into a single unit, the sounding device 6, configured to control the transmission coefficient to control the volume level at the listening point, and the communication line 8 has a constant transmission coefficient.

 The spatial sound reproducing system (Fig. 1) operates as follows.

 Through the receiving element of the probing device 6, sound signals are received that are present at the point of listening to direct acoustic waves from the speaker 4, reflected from the walls and other objects of the room acoustic waves from the speaker 4, as well as acoustic noise and noise.

 The received signal ("distorted") is converted into an electrical signal and through the communication line 8 is fed to the first input of the device 7 for automatic regulation of the amplitude-frequency characteristics. As the communication line 8, a cable communication line 8 or a wireless communication line 8 can be used, for example, an information transmission channel using radio waves or infrared waves.

 The level of the electric ("distorted") signal that is fed to the first input of the device for automatically adjusting the frequency response can be changed by the consumer by adjusting the transmission coefficient of the probing device 6 or communication line 8.

 This adjustment is carried out by the appropriate regulatory body volume control 5.

The volume control 5 can be performed by any known schemes for regulating the transfer coefficient of a four-terminal device or a communication system (active or passive). The nature of the regulation of the transmission coefficient can be either uniform or uneven for the frequencies of sound reproduction (with or without loudness). For example, the volume control 5 can be made in the form of a resistive voltage divider with loudness circuits passive regulator 5, feedback regulator of amplification stages
active regulator 5, regulator of the percentage of modulation or deviation of the frequency of the radio signal, when using the communication channel 8 of the signal as the communication line, etc.

 At the second input of the device 7, a “reference” (converted) signal from the signal source 1 is supplied.

 The signal conversion is carried out using the device 2 regulation of the amplitude-frequency characteristics.

 The device 7 for automatically adjusting the frequency response compares the "reference" and "distorted" signals arriving at it. Comparison of signals is carried out in the spectral region, the levels of the spectral components of these signals at the corresponding frequencies are compared.

 Depending on the magnitude of the difference in the levels of the spectral components of the signals, the device 7 generates control signals that are proportional to the amount of distortion (the difference in the amplitudes of the spectral components at the corresponding frequencies).

 The control signals change the state of the transfer characteristics (frequency response and transmission coefficient) of the device 7 so that the "reference" signal, passing through the device 7, undergoes predistortion and is further amplified by the low-frequency amplifier 3, emitted by the speaker 4 and acoustically formed at the listening point, is perceived by the listener without distortion - in the form of a "reference" electrical signal.

 In other words, the device 7 for automatically adjusting the frequency response is a block of correlation signal processing or an optimal (matched) filter that works in real time and allows you to quickly compensate for distortions in the audio path; amplifier 3 low frequency loudspeaker 4 acoustic room - listener.

 Using the device 2 to regulate the amplitude-frequency characteristics in the circuit of the formation of the "reference" electrical signal allows you to compensate for frequency distortion, filter the noise and noise of the signal source 1, as well as in the embodiment of the invention, and normalize its level.

 It is known that the perception of sound vibrations at different frequencies and with different levels of sound pressure depends on the individual characteristics of each person’s hearing. Particularly noticeable is the dependence of the perception of higher frequencies on age. Therefore, in order for the subjective perception of loudness to vary proportionally in the entire spectrum of frequencies of sound reproduction, it is necessary to adjust the frequency response of the signal.

 To adjust the amplitude-frequency characteristics taking into account the individual characteristics of the listener in the proposed system, the device 2 controls the amplitude-frequency characteristics, which can be performed, for example, in the form of a tone control or multi-band equalizer (graphic equalizer).

 In addition, the device 2 control the frequency response can be used for additional filtering of the signal from the source 1, containing interference and noise or having noticeable frequency distortion.

 For example, if a radio receiver of broadcasting stations is used as the signal source 1, the output signal may contain interference noise, low-frequency noise in the form of a background, broadcast noise, distortion of the signal spectrum due to the characteristics of the amplitude-frequency characteristics of the intermediate-frequency amplifier of a particular radio receiver, and the accuracy of tuning to broadcasting station, etc.

 If a tape recorder is used as the signal source 1, then amplitude-frequency distortions are possible due to a scatter in the electrical parameters of the recording and reproducing heads, inaccurate coincidence of the recording tracks, imperfection of the amplitude-frequency characteristics of the frequency response preamps, etc.

 To compensate for the specified amplitude-frequency distortion, as well as to carry out optimal filtering of noise and noise of the signal source 1 in the proposed spatial sound reproducing system allows the device 2 control the frequency response.

 In contrast to the volume control in classical sound reproducing systems providing absolute control of the sound level of loudspeaker 4, the proposed spatial sound reproducing system provides control of the sound level of loudspeaker 4 taking into account the distance from the listener. The lower the signal level at the first input of the automatic frequency control device 7, set by the consumer using the volume control 5 when adjusting the transmission coefficient of the probing device 6 or communication line 8, the higher the level of the sound signal at the listening point.

 The maximum sound level at the listening point, for example 110 dB, corresponds to a zero signal level at the first input of the device 7.

 If the consumer changes his location relative to the loudspeaker 4, for example, approaches it, then accordingly the sound level of the loudspeaker 4 changes, i.e. it decreases in such a way that a certain (selected by the consumer) volume level is stored at the listening point.

 The automatic formation of a predetermined volume level at the listening point provides a device 7 for automatically adjusting the frequency response in accordance with the above-described principle of its operation.

 Compared with the spatial sound reproducing system (SU, patent, N 2038704), the proposed system has circuitry advantages when adjusting the volume at the listening point: a) a separate volume control circuit with feedback is not used to form the selected volume level at the listening point (broadband comparison scheme is excluded and a circuit for electrical volume control), which greatly simplifies the design of the system; b) the time required for self-adaptation of the system is reduced.

 It is known that due to the characteristics of the human hearing organs, with a decrease in the volume level at the listening point, a decrease in the perception of low and high sound frequencies is observed. Therefore, usually in classical spatial sound-reproducing systems, thin-compensated volume controls are used, which simultaneously with decreasing or increasing the sound volume of the loudspeaker 4 change the frequency response of the amplifier device so that it corresponds to the well-known curves of equal loudness.

 The use of loudly controlled volume controls in classical sound reproducing systems (without using the principle of correlation signal processing) is unlawful.

 Indeed, the location of the listener, the location of the speaker 4 in the room can generally be different, and therefore, the distance from the listener to the speaker 4 can also be different. For example, in a typical residential environment, the distance from the listener to the loudspeaker 4 can be about 0.5-5.0 m, while the sound pressure level, depending on the specific situation, can differ by 3-10 dB.

 Classical sound reproducing systems do not take into account the above features of sound reproduction in domestic conditions. Therefore, the use of loudly-controlled volume controls 5 in their composition is not entirely legitimate.

 In the proposed spatial sound reproducing system, as noted, it is possible to provide a pre-selected volume level at the listening point, so it is advisable to adjust the volume in the loudness mode.

 Loudly compensated volume control can be obtained if the transmission coefficient of the sounding device 6 or communication line 8 is not uniformly applied to the audio frequencies, for example, the volume control 5 can be made in the form of a resistive voltage divider with corresponding frequency correction circuits.

 When playing audio in a domestic environment, for example, in a living room, a cabin of a ship or a passenger compartment, acoustic interference and noise are usually present. The nature of these noises and interferences is different.

 Noises and interferences external in nature of origin can be distinguished, as well as secondary noises and interferences.

 Noises and interferences that are external in nature of origin can include: noise from the street, noise from the walls of neighboring rooms, internal noise of the room (for example, transformer noise, fluorescent lamps, etc.) during sound reproduction in a residential building; the noise of a running engine or other car systems, street noise through a window that is not tightly closed, etc. when playing in the car; noise of the sea in the cabin of the ship.

 Noises external in nature of origin can be conditionally divided into two classes of noise. Noises with a spectrum slowly varying in time can be attributed to the first class, and noise with a spectrum that is rapidly changing in time (pulsating) to the second class.

 Secondary in nature of origin of noise can be attributed to: rattling of glasses, dishes and other objects when reproducing at high volume in residential premises; rattling of decorative panels of the passenger compartment; rattle of the speaker cone 4 or the false panel of the speaker when the sound volume is high.

 The proposed spatial sound reproducing system allows you to filter these interference and noise.

 When secondary noise and interference occur due to the action of high-intensity sound waves on the resonant systems of the living room, secondary sound waves arise. The spectrum of these waves has a fundamental resonant frequency of secondary vibrations and harmonic components. The number of harmonics and their amplitude depend on the shape and physical properties of the resonance system.

 When these waves propagate indoors, they reach the listening point at which an aggregate sound field is formed, which is a superposition of the direct waves reflected from the walls of the useful signal and, accordingly, the direct and reflected secondary waves (interference).

 The spectrum of the total sound field at the listening point is very different from the spectrum of the "reference" signal.

 In accordance with the described principle of operation of the proposed spatial sound reproducing system in the device 7 for automatically adjusting the frequency response, the reference signal is pre-distorted until the spectrum of the acoustic signal at the listening point matches the accuracy of the reference signal spectrum with maximum achievable accuracy in a particular acoustic situation. In this case, optimal (by the criterion of the minimum difference in the amplitudes of the spectral components) filtering of the reproduced signal occurs. As a result of this filtering, an automatic “search” and a decrease in the gain at frequencies causing spurious resonances and secondary noise are carried out. For the listening point, the dynamic equilibrium and balance mode of the acoustic aggregate signal sets in, the spectrum of which at the listening point, perceived by the probing device 6, and therefore by the listener, approaches the spectrum of the reference signal as much as possible.

 Theoretically, secondary noise can be completely filtered using the proposed system for the "reference" signal having a spectrum of the type "pink" noise. However, the spectra of most musical and especially speech sources of signal 1 have a rapidly changing (pulsating) type of spectrum, therefore, for real sound signals, only partial suppression of secondary noise can be obtained. With the pulsating nature of the reproduced signal, the system due to the inertia of the work (the inertia of the work is determined by the correlation time of the signals) will delay and suppress spurious oscillations (secondary noise) with a delay.

If there are noises external in nature of the origin of origin, then in accordance with the described principle of the spatial sound-absorbing system, the spectrum of the “reference” signal is optimally filtered taking into account the spectral components of external noise for the listening point
there is an automatic “search” of the spectral components of interference and a corresponding change in the reproduced signal level at these frequencies. As a result, the signal is masked by the signal, and the spectrum of the acoustic signal at the listening point becomes extremely close to the spectrum of the "reference" signal.

 However, the complete suppression of external interference in the general case does not occur due to the difference between the spectra of the "reference" signal and the interference spectrum (small correlation).

 The proposed spatial sound reproducing system can most effectively suppress (mask) narrow-band, stationary (slowly varying in time) interference when playing musical fragments.

 When playing musical phonograms, especially pop and rock music, the low-frequency part of the signal spectrum is formed by a bass guitar, drums and, less often, wind or keyboard (electronic synthesizers) instruments. In the low-frequency region, the temporal nature of the change in the spectrum differs from the mid-frequency and high-frequency parts of the spectrum of sound reproduction, the changes in the spectrum are slower, therefore, when filtering low-frequency interference (for example, wind, sea, street noise, etc.), the delay of the "distorted" reference signal during the system self-adaptation time is less noticeable and a relatively large part of the time the low-frequency signal at the listening point is reproduced in the corrected form.

 Thus, the proposed spatial sound reproducing system allows to increase the signal-to-noise ratio (noise) for the listening point and thereby the quality of sound reproduction for the individual listener.

 Some types of signal sources, such as tuners or tape recorders, do not provide a nominal output level.

 So, when tuning to broadcasting stations, different levels of the output signal are possible due to the fading of the radio signal of different modulation depths, and when playing magnetic recordings made with different levels on different types of film, the output signal can also significantly (by 3-10 dB) rated.

 To normalize the output level of such sources of signals 1, the device 2 for regulating the amplitude-frequency characteristics can be configured to automatically control the level of the output signal. For example, at the output of the device for controlling the frequency response, made in the form of a tone control or multi-band equalizer, an automatic gain control device similar to the known recorder automatic level control (ARUZ) devices can be installed.

 Due to the normalization of the signal level at the output of the device for controlling the frequency response, it is possible to further increase the accuracy of the correction of the amplitude-frequency characteristics of the signal at the listening point and, therefore, increase the reliability of sound reproduction.

 The correction of the sound reproduction path and the objective adjustment of the sound field parameters at the listening point to a “reference” signal depend on the signal-to-noise (noise) ratio in the room, electrical indicators and features of the circuitry solutions of the equipment, as well as the accuracy of the preliminary setup and calibration of the equipment, the stability of the parameters of the radioelement base .

 The equipment can be tuned in special acoustic studios (anechoic chambers) using noise generators and multi-channel spectrum analyzers as control and measuring equipment.

 The technical solution (Fig. 1) is described for one channel of sound reproduction (monophonic mode of sound reproduction). It is clear that in a similar way a system can be built for two or four sound reproduction channels. In these cases, the device 7 of the automatic control of the frequency response should have an appropriate number of inputs and outputs.

 As one of the options that implements the functional diagram of the spatial sound reproducing system, a device made according to the circuit shown in FIG. 2.

 The sounding device 6, in particular, can be made in the form of a microphone 9, a volume control 5, a radio transmitting device 10, equipped with a transmitting antenna 11, which are connected in series, the communication line 8 in the form of a radio receiving device 12 with a receiving antenna 13, the output of which is the output of the communication line 8 and is connected to the first input of the device 7 for automatic regulation of the amplitude-frequency characteristics.

 The device operates (Fig. 2) as follows.

 By means of a microphone 9, a sounding device 6, a “distorted” acoustic signal is received at the listening point and converted into an electrical signal.

 An electrical signal is supplied to the volume control 5, through which the transmission coefficient of the probing device 6 is adjusted.

 The signal from the volume output 5 modulates the radio signal of the radio transmitting device 10. Radiation of the radio signal is carried out by means of a radio transmitting antenna 11.

 The radio receiver 12 through the receiving antenna 13 receives the radio signal and performs its demodulation, again turning into an electrical signal. From the output of the radio receiving device 12, the signal is supplied to the first input of the device 7 for automatic regulation of the frequency response, which ensures optimal filtering of the signal in accordance with the described algorithm of its operation.

 The device 7 for automatically adjusting the frequency response can be performed according to any well-known schemes, for example, according to the scheme of the device 7 described in SU, patent, N 2038704.

 Since the volume control 5 is structurally integrated with the sounding device 6 and, like the sounding device 6, is located in the immediate vicinity of the listening point, an additional technical result obtained by the implementation of the embodiment of the invention is the possibility of remote (radio-controlled) volume adjustment directly from the point listening.

 The proposed spatial sound reproducing system can be most successfully used in radio engineering for high-quality sound reproduction from various primary sources: tape recorders, tuners, stereo players, in rooms with poor, unknown or changing acoustic characteristics, for example, in living rooms, ship cabins, car interiors.

 The system can be structurally combined with a sound reproducing device (radio, television, music center, etc.) or made separately as a functional unit and can be completed in blocks with various sound reproducing equipment, while the requirements for the amplitude-frequency characteristics of the low-frequency amplifier 3 and loudspeaker 4 can be significantly reduced.

Claims (7)

 1. A spatial sound reproducing system comprising a signal source, an amplitude-frequency response control device, a low-frequency amplifier, a loudspeaker connected in series, and a volume control, a sounding device, an automatic amplitude-frequency response control device, a communication line, wherein the output of the sounding device is the communication line is connected to the first input of the device for automatic regulation of the amplitude-frequency characteristics, and the probing the device is installed at the listening point, characterized in that the second input of the device for automatically controlling the amplitude-frequency characteristics is connected to the output of the signal source through the device for regulating the amplitude-frequency characteristics, the output of the device for automatically regulating the amplitude-frequency characteristics is connected to the input of the low-frequency amplifier, and the probe device or the communication line is configured to control the transmission coefficient to control the volume level at the point disobedience.  2. The system according to claim 1, characterized in that the device for regulating the amplitude-frequency characteristics is made in the form of a tone control.  3. The system according to claim 1, characterized in that the device for regulating the amplitude-frequency characteristics is made in the form of a multi-band equalizer.  4. The system according to claim 1, characterized in that the adjustment of the transmission coefficient of the probing device or communication line is carried out uniformly for sound reproduction frequencies.  5. The system according to claim 1, characterized in that the regulation of the transmission coefficient of the probing device or communication line is uneven for the frequencies of sound reproduction.  6. The system according to claim 1, characterized in that the device for regulating the amplitude-frequency characteristics is configured to automatically control the level of the output signal.  7. The system according to claim 1, characterized in that the probing device is made in the form of a microphone, volume control, radio transmitting device equipped with a transmitting antenna, which are connected in series, communication lines in the form of a radio receiving device with a receiving antenna, the output of which is the output of the communication line and connected to the first input of the device for automatic regulation of the amplitude-frequency characteristics.

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