Noise generation circuit, noise generation method and recording shielding equipment

Abstract

The embodiment of the invention discloses a noise generation circuit, a noise generation method and recording shielding equipment, which are used for preventing signals from being monitored. According to the embodiment of the invention, a signal source is connected with a signal generation module and a first modulation module; and the signal generation module is used for sending at least one first ultrasonic wave to a receiving end. The first modulation module is connected with the first noise module, and the first modulation module is used for receiving a first noise signal generated by the first noise module and modulating the first noise signal and the frequency signal to obtain a first modulation signal; the first driving module is connected with the first modulation module and the first probe module, and the first driving module is used for generating a first driving signal according to the first modulation signal and sending the first driving signal to the first probe module. The first probe module sends a second ultrasonic wave according to the first driving signal so as to generate a difference frequency signal overlapped with a part of frequency band or all frequency band of the protected audio signal with the first ultrasonic wave.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of signal shielding, and in particular to a noise generating circuit, a noise generating method, and a recording shielding device. Background Art

[0002] With the continuous development of science and technology, people's production level is constantly improving. In order to improve work efficiency, people have the need for remote communication, and audio-related technologies have emerged. Through audio-related technologies, the audio signal of one party can be transmitted to the other party, realizing the long-distance communication of information. Among them, due to the need for confidentiality, recording shielding technology is also widely used. There are currently three main types of recording shielding technologies, one is electromagnetic wave technology, the other is white noise technology, and the other is ultrasonic technology. Among them, electromagnetic wave technology and white noise technology have great limitations and are no longer commonly used, so the existing solutions usually use ultrasonic waves for recording shielding.

[0003] However, when an ultrasonic probe is used for recording shielding, after the interference signal formed by the ultrasonic wave reaches the recording device, the recording device may filter out the interference signal, so that the effect of recording shielding cannot be achieved. Summary of the invention

[0004] The embodiments of the present application provide a noise generating circuit, a noise generating method and a recording shielding device, which can improve the reliability of recording shielding.

[0005] A first aspect of an embodiment of the present application provides a noise generating circuit, comprising: a signal source, a first noise module, a first modulation module, a first driving module, a first probe module and a signal generating module;

[0006] The signal source is connected to the signal generating module and the first modulation module respectively, and the signal source is used to generate a frequency signal of a preset frequency;

[0007] The signal generating module is used to send at least one first ultrasonic wave to the receiving end according to the frequency signal;

[0008] The first modulation module is connected to the first noise module, and the first modulation module is used to receive the first noise signal generated by the first noise module, and modulate the first noise signal and the frequency signal received from the signal source to obtain a first modulation signal;

[0009] The first driving module is respectively connected to the first modulation module and the first probe module, and the first driving module is used to generate a first driving signal based on the first modulation signal, and send the first driving signal to the first probe module; the first probe module sends a second ultrasonic wave based on the first driving signal to generate a difference frequency signal with the first ultrasonic wave that overlaps with part or all of the frequency band of the protected audio signal.

[0010] Optionally, the signal generating module includes: a driving submodule and a probe submodule;

[0011] The input end of the driving submodule is connected to the signal source, and the output end of the driving submodule is connected to the probe submodule. The driving submodule is used to generate a second driving signal according to the frequency signal and send the second driving signal to the probe submodule; the probe submodule sends one of the first ultrasonic waves to the receiving end, wherein the frequency band of the first ultrasonic wave is the same as that of the frequency signal, and the frequency band of the first noise signal overlaps with part or all of the frequency band of the protected audio signal.

[0012] Optionally, the signal generating module includes at least one signal generating submodule, each of which includes: a noise unit, a modulation unit, a driving unit and a probe unit, and the modulation unit of each of the signal generating submodules is connected to the signal source;

[0013] In each of the signal generating submodules, the modulation unit is connected to the noise unit, the noise unit is used to generate a second noise signal, the modulation unit is used to receive the second noise signal sent by the noise unit and the frequency signal sent by the signal source, and modulate the frequency signal and the second noise signal to obtain a second modulation signal;

[0014] In each of the signal generating submodules, the input end of the driving unit is connected to the modulation unit, the output end of the driving unit is connected to the probe unit, the driving unit is used to generate a third driving signal according to the second modulation signal, and send the third driving signal to the probe unit; the probe unit sends one of the first ultrasonic waves to the receiving end;

[0015] The frequency difference between the first noise signal and at least one of the second noise signals overlaps with the entire frequency band or part of the frequency band of the protected audio signal; and / or the frequency band difference between each of the second noise signals and at least another second noise signal in all the second noise signals overlaps with the entire frequency band or part of the frequency band of the protected audio signal.

[0016] Optionally, the signal generating module further includes: a driving submodule and a probe submodule;

[0017] The input end of the driving submodule is connected to the signal source, and the output end of the driving submodule is connected to the probe submodule. The driving submodule is used to generate a fourth driving signal according to the frequency signal and send the fourth driving signal to the probe submodule; the probe submodule sends a third ultrasonic wave to the receiving end according to the fourth driving signal, so that the first ultrasonic wave, the second ultrasonic wave and the third ultrasonic wave generate a difference frequency signal that overlaps with part or all of the frequency band of the protected audio signal.

[0018] Optionally, the first noise signal has a preset frequency bandwidth.

[0019] Optionally, the first noise signal is a random signal.

[0020] Optionally, the frequency of the frequency signal is greater than or equal to 25 kHz and less than or equal to 40 kHz.

[0021] A second aspect of an embodiment of the present application provides a noise generation method, including:

[0022] Generate a frequency signal of a preset frequency;

[0023] Processing the frequency signal to obtain at least one first ultrasonic wave;

[0024] Based on a preset rule, generating a first noise signal;

[0025] Modulating the first noise signal and the frequency signal to obtain a first modulated signal, and generating a second ultrasonic wave according to the first modulated signal;

[0026] The second ultrasonic wave and the first ultrasonic wave are sent to a receiving end to generate a difference frequency signal overlapping a part of the frequency band or the whole frequency band of the protected audio signal.

[0027] Optionally, the processing the frequency signal to obtain at least one first ultrasonic wave includes:

[0028] Converting the frequency signal into a corresponding second driving signal based on a preset conversion rule;

[0029] generating one of the first ultrasonic waves corresponding to the second driving signal;

[0030] The frequency band of the first ultrasonic wave is the same as that of the frequency signal, and the frequency band of the first noise signal overlaps with the frequency band of the protected audio signal.

[0031] Optionally, before processing the frequency signal to obtain at least one first ultrasonic wave, the method further includes:

[0032] generating at least one second noise signal;

[0033] The processing of the frequency signal to obtain at least one first ultrasonic wave comprises:

[0034] Performing modulation processing on each of the second noise signals and the frequency signal respectively to obtain a second modulation signal corresponding to the second noise signal;

[0035] Converting the second modulation signal into a corresponding third drive signal based on a preset conversion rule;

[0036] generating the first ultrasonic wave corresponding to the third driving signal;

[0037] The frequency difference between the first noise signal and at least one of the second noise signals overlaps with the entire frequency band or part of the frequency band of the protected audio signal; and / or the frequency band difference between each of the second noise signals and at least another second noise signal in all the second noise signals overlaps with the entire frequency band or part of the frequency band of the protected audio signal.

[0038] Optionally, the method further includes:

[0039] Converting the frequency signal into a corresponding fourth driving signal based on a preset conversion rule;

[0040] generating a third ultrasonic wave corresponding to the fourth driving signal;

[0041] The sending the second ultrasonic wave and the first ultrasonic wave to the receiving end to generate a difference frequency signal overlapping a part of the frequency band or the whole frequency band of the protected audio signal includes:

[0042] The third ultrasonic wave, the second ultrasonic wave and the first ultrasonic wave are sent to a receiving end to generate a difference frequency signal overlapping a part of the frequency band or the whole frequency band of the protected audio signal.

[0043] A third aspect of an embodiment of the present application provides a recording shielding device, comprising the noise generating circuit as described above.

[0044] It can be seen from the above technical solutions that the embodiments of the present application have the following advantages:

[0045] The noise generating circuit provided in the embodiment of the present application can generate a frequency signal of a preset frequency, obtain a first ultrasonic wave according to the frequency signal, and finally obtain a second ultrasonic wave by modulating the frequency signal and the first noise signal, and send the first ultrasonic wave and the second ultrasonic wave to the receiving end at the same time. Due to the nonlinear acoustic effect of the propagation medium, a difference frequency signal overlapping with part or all of the frequency band of the protected audio signal will be generated during the propagation of the first ultrasonic wave and the second ultrasonic wave. Since the difference frequency signal overlaps with the frequency band of the protected audio signal, it can prevent the recording device from filtering out the difference frequency signal, thereby improving the reliability of recording shielding. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 A module schematic diagram of an embodiment of a noise generating circuit disclosed in the present application;

[0047] Figure 2 A circuit diagram of an embodiment of a noise generating circuit disclosed in the present application;

[0048] Figure 3 A circuit diagram of another embodiment of a noise generating circuit disclosed in the present application;

[0049] Figure 4 A circuit diagram of another embodiment of a noise generating circuit disclosed in the present application;

[0050] Figure 5 A circuit diagram of another embodiment of a noise generating circuit disclosed in the present application;

[0051] Figure 6 A schematic diagram of an embodiment of a noise generation method disclosed in the present application;

[0052] Figure 7 A schematic diagram of another embodiment of a noise generation method disclosed in the present application;

[0053] Figure 8 A schematic diagram of a spectrum of a portion of a signal generated by a nonlinear effect in an embodiment disclosed in the present application;

[0054] Fig. 9 A schematic diagram of another embodiment of a noise generation method disclosed in the present application;

[0055] Fig.10 A schematic diagram of a spectrum of a portion of a signal generated by a nonlinear effect in another embodiment disclosed in the present application;

[0056] Fig.11 This is a schematic diagram of another embodiment of a noise generation method disclosed in the present application. DETAILED DESCRIPTION

[0057] The present application is further described in detail below in conjunction with the accompanying drawings.

[0058] The embodiments of the present application provide a noise generating circuit, a noise generating method and a recording shielding device for preventing a signal from being monitored.

[0059] There are many scenarios in life where recording shielding is required. In the existing solutions, ultrasonic waves are used to achieve recording shielding. The ultrasonic probe generates ultrasonic waves based on the driving signal. The ultrasonic waves are transmitted in the air and form interference signals. When the interference signal reaches the recording device, it can interfere with the recording device to achieve anti-recording. However, when the interference signal generated in the traditional solution reaches the recording device, the recording device may filter out the interference signal. In addition, the frequency of the ultrasonic waves emitted by all ultrasonic probes at the same time is fixed, and the sound pressure level is large, which will also produce harsh noise.

[0060] In order to solve the above problems, the embodiments of the present application provide a noise generating circuit, a noise generating method and a recording shielding device to generate at least two ultrasonic waves with different frequencies to be transmitted to the receiving end, and the difference frequency signal generated between the ultrasonic waves overlaps with the frequency band of the protected audio signal, which can prevent the recording device from filtering out the difference frequency signal, thereby improving the reliability of recording shielding.

[0061] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0062] The terms "first", "second", "third", "fourth", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0063] The noise generating circuit of this application is described below. Figure 1 and Figure 2, an embodiment of the noise generating circuit of the present application includes: a signal source 1, a first noise module 2, a first modulation module 3, a first driving module 4, a first probe module 5 and a signal generating module 6. The noise generating circuit provided in this embodiment can be applied to a recording shield or other application scenarios where noise needs to be generated, which is not specifically limited here.

[0064] The signal source 1 is connected to the signal generating module 6 and the first modulation module 3 respectively, and the signal source 1 is used to generate a frequency signal of a preset frequency. Among them, the signal source 1 may include a processor, a single chip microcomputer or an oscillator, which is not limited here. The frequency signal is, for example, a sinusoidal signal, a pulse signal or other signal with a specific frequency, and the frequency of the frequency signal can be set according to actual needs, which is not limited here. For example, the frequency of the frequency signal can be greater than or equal to 25 kHz and less than or equal to 40 kHz, that is, the frequency of the frequency signal can be any value between 25 kHz and 40 kHz. In this embodiment, setting the frequency of the frequency signal to 25 kHz to 40 kHz is a relatively ideal value, which will not cause the ultrasonic wave to decay too fast in the air due to the high frequency and fail to meet the requirements of recording shielding, nor will it cause excessive noise due to the low frequency selection.

[0065] The signal generating module 6 is used to send at least one first ultrasonic wave to the receiving end according to the frequency signal. The first ultrasonic wave is an ultrasonic wave with a certain frequency, and the frequency of the first ultrasonic wave can be the same as the frequency signal, or can be a frequency signal with other frequencies superimposed thereon.

[0066] The first noise module 2 can generate a first noise signal. The first modulation module 3 is connected to the first noise module 2, and the first modulation module 3 is used to receive the first noise signal generated by the first noise module 2, and modulate the first noise signal and the frequency signal received from the signal source 1 to obtain a first modulation signal. Among them, the first noise signal is noise, and specifically, the bandwidth value of the first noise signal can be within a preset bandwidth range. In other words, the first noise signal has a certain bandwidth, that is, the energy of the first noise signal is distributed at multiple frequency points, so the power spectrum density is low and it will not be easily heard by people. Further, the first noise signal can be a random signal, that is, the first noise signal belongs to random noise. Further, the frequency of the first noise signal can change over time, that is, the frequency of the first noise signal is not fixed, so that harsh noise can be avoided.

[0067] The first modulation module 3 is used to modulate the signal, and can make at least two input signals add, subtract, or multiply, etc., and set the specific circuit structure according to actual needs to achieve the corresponding function. The first modulation module 3 is, for example, a mixer. In this embodiment, the first modulation module 3 can modulate the first noise signal onto the frequency signal, that is, the frequency of the first modulation signal output by the first modulation module 3 is the sum of the frequency of the frequency signal and the frequency of the first noise signal.

[0068] The first driving module 4 is connected to the first modulation module 3 and the first probe module 5 respectively, and the first driving module 4 is used to generate a first driving signal according to the first modulation signal, and send the first driving signal to the first probe module 5. The first probe module 5 sends a second ultrasonic wave according to the first driving signal to generate a difference frequency signal overlapping with part or all of the frequency band of the protected audio signal with the first ultrasonic wave. Among them, regarding the frequency band of the difference frequency signal generated by the first ultrasonic wave and the second ultrasonic wave, if the frequency of the first ultrasonic wave generated by the signal generating module 6 is the same as the frequency of the frequency signal, the frequency band of the difference frequency signal is the same as the frequency band of the first noise signal generated by the first noise module 2; or, if the frequency of the first ultrasonic wave generated by the signal generating module 6 is different from the frequency of the frequency signal, the frequency band of the difference frequency signal is jointly determined by the first noise module 2 and the signal generating module 6. These are all within the protection scope of this embodiment. Overlapping with part or all of the frequency band of the protected audio signal, in other words, the frequency band of the difference frequency signal is at least the same as part of the frequency band of the protected audio signal. Regarding the protected audio signal, assuming that the noise generating circuit is applied to a recording shield, the protected audio signal is a voice signal that does not want to be recorded by an illegal recording device. If the specific application scenario of the recording jammer is a conference room, then everyone's speech in the meeting is a protected audio signal.

[0069] Among them, the first driving module 4 is a circuit that drives the first probe module 5 to work, for example, amplifies the first modulated signal to generate a first driving signal. The first driving module 4, for example, includes an operational amplifier and peripheral circuits to achieve power amplification. The first probe module 5, for example, includes an ultrasonic probe, which can convert electrical energy into ultrasonic waves, such as a piezoelectric transducer. Among them, further, the sound pressure level of the ultrasonic wave (such as the first ultrasonic wave and / or the second ultrasonic wave) can be controlled to be greater than a certain value, and the sound pressure level of the difference frequency signal can be made greater than the maximum sound pressure level of the microphone at the receiving end, so that the audio input device (such as a microphone) of the recording shielding device can be distorted to improve the recording shielding effect.

[0070] In the above-mentioned noise generating circuit provided in the embodiment of the present application, the signal source 1 can generate a frequency signal of a preset frequency, and the signal generating module 6 generates and emits a first ultrasonic wave according to the frequency signal. At the same time, the first modulation module 3 modulates the first noise signal and the frequency signal, and then generates and emits a second ultrasonic wave through the first driving module 4 and the first probe module 5. Due to the nonlinear acoustic effect of the propagation medium, a difference frequency signal will be generated during the propagation of the first ultrasonic wave and the second ultrasonic wave, and the difference frequency signal overlaps with part or all of the frequency bands of the protected audio signal. Since the purpose of the recording device is to illegally obtain the protected audio signal, a filtering circuit will not be set to filter out the protected audio signal. The difference frequency signal generated in this embodiment is at least partially the same as the protected audio signal. Therefore, it can at least prevent the recording device from filtering out all the difference frequency signals. Therefore, it can at least ensure that the recording device records part of the noise, so that the recording device cannot extract the protected audio signal, thereby improving the reliability of recording shielding. In addition, since the frequency of the difference frequency signal is related to the first noise signal, the frequency can be changed, and the problem of harsh noise caused by the fixed frequency of the ultrasonic wave in the traditional scheme can be avoided, so that the recording shielding operation is not easily detected by the user.

[0071] Furthermore, if the first noise signal is a signal with a certain bandwidth, then the difference frequency signal is also at least a signal with a certain bandwidth, that is, the power spectrum density of the difference frequency signal is lower. In this way, the possibility of being heard by the human ear can be further reduced to improve the safety of recording shielding.

[0072] Furthermore, if the first noise signal is random noise, the difference frequency signal also includes at least random noise. Since random noise is difficult to crack, once the random noise is recorded into the recording device, the difficulty of the recording device to restore the protected audio signal is further increased, thereby further improving the reliability of preventing illegal recording.

[0073] There are many options for the structure of the signal generating module 6, which can be set according to actual needs and are not limited here. The following three embodiments are used to specifically illustrate three situations of the signal generating module 6.

[0074] exist Figure 2 Based on the corresponding embodiments, please refer to Figure 3 Another embodiment of the noise generating circuit of the present application includes: a signal source 1, a first noise module 2, a first modulation module 3, a first driving module 4, a first probe module 5 and a signal generating module 6. Figure 2 Based on the corresponding embodiment, specifically, the signal generating module 6 includes: a driving submodule 61 and a probe submodule 62. Figure 1 , Figure 2The principles of the same modules in the embodiments will not be repeated here, and reference may be made to the above content.

[0075] The input end of the driving submodule 61 is connected to the signal source 1, and the output end of the driving submodule 61 is connected to the probe submodule 62. The driving submodule 61 is used to generate a second driving signal according to the frequency signal, and send the second driving signal to the probe submodule 62. The probe submodule 62 sends a first ultrasonic wave to the receiving end, wherein the frequency band of the first ultrasonic wave is the same as that of the frequency signal, and the frequency band of the first noise signal overlaps with part or all of the frequency band of the protected audio signal.

[0076] The driving submodule 61 is a circuit for driving the probe submodule 62 to work, for example, amplifying the frequency signal to generate a second driving signal. The driving submodule 61 includes, for example, an operational amplifier and peripheral circuits to achieve power amplification. The probe submodule 62 includes, for example, an ultrasonic probe that can convert electrical energy into ultrasonic waves, such as a piezoelectric transducer.

[0077] Now combined Figure 8 The working principle of this embodiment is described by way of example. The signal source 1 generates a frequency signal f1 of a preset frequency band, and the first noise module 2 also generates a first noise signal f N , where the first noise signal f N The frequency band of the first noise signal f overlaps part of or all of the frequency band of the protected audio signal. If the frequency band of the protected audio signal is 300 to 500 Hz, the first noise signal f N The frequency band of the protected audio signal may be 200 to 400 Hz, and the two frequency bands partially overlap. If the frequency band of the protected audio signal is 300 to 500 Hz, the first noise signal f N The frequency band of can be 300 to 500 Hz, then the two frequency bands completely overlap. The first noise signal and the frequency signal are mixed and modulated by the first modulation module 3 to obtain a first modulation signal, which is converted into a first drive signal by the first drive module 4. The first drive signal is converted into a second ultrasonic wave with a frequency band of f2 by the first probe module 5, and f2 = f1 + f N In addition, the frequency signal is passed through the driving submodule 61 and the probe submodule 62 to obtain the first ultrasonic wave with a frequency band of f1. Under the nonlinear effect of the propagation medium, the two ultrasonic waves will generate a difference frequency signal f2-f1=f N , and frequency signal f1+f2=2f1+f N, original signals f1, f2, and the second harmonic signals 2f1, 2f2 and other higher harmonics of the original signals. According to the principle of sound absorption, the higher the frequency of the sound wave, the easier it is to be absorbed by the propagation medium, that is, the sum frequency signal (f1+f2), the original signals f1, f2 and the higher harmonic signals will decay quickly, and the main remaining difference frequency signal f2-f1 will eventually reach the receiving end, and the frequency band of the difference frequency signal overlaps partly or completely with the protected audio signal, which can achieve shielding.

[0078] Therefore, in this embodiment, two ultrasonic waves are emitted simultaneously, one of which is a pure ultrasonic wave, namely the first ultrasonic wave, and the other is an ultrasonic wave superimposed with noise, namely the second ultrasonic wave. Due to the nonlinear acoustic effect of the propagation medium, a difference frequency signal will be generated during the propagation of the first ultrasonic wave and the second ultrasonic wave, and the frequency band of the difference frequency signal is the same as that of the first noise signal. Since the difference frequency signal overlaps with the frequency band of the protected audio signal, it can prevent the recording device from filtering out the difference frequency signal, thereby improving the reliability of recording shielding. And since the frequency of the difference frequency signal can be changed, it can also avoid the problem of harsh noise caused by the fixed frequency of the ultrasonic wave in the traditional scheme, so that the recording shielding operation is not easily noticed by the user.

[0079] exist Figure 2 Based on the corresponding embodiments, please refer to Figure 4 Another embodiment of a noise generating circuit of the present application includes: a signal source 1, a first noise module 2, a first modulation module 3, a first driving module 4, a first probe module 5 and a signal generating module 6.

[0080] exist Figure 2On the basis of the corresponding embodiment, specifically, the signal generating module 6 includes at least one signal generating submodule 63. For the convenience of description, one signal generating submodule 63 is used for explanation in this embodiment. Each signal generating submodule 63 includes: a noise unit 631, a modulation unit 632, a driving unit 633 and a probe unit 634, and the modulation unit 632 of each signal generating submodule 63 is connected to the signal source 1. Among them, the noise unit 631 is used to generate a second noise signal. The noise unit 631 can be a noise generator or a specific circuit set by itself, which is not limited here. Among them, the second noise signal is a noise with a frequency band different from the first noise signal. Further, the second noise signal is a signal with a certain bandwidth, and the difference frequency signal (the difference frequency signal of the first noise signal and the second noise signal, the difference frequency signal of two different second noise signals) is also at least a signal with a certain bandwidth, that is, the power spectrum density of the difference frequency signal is low, so that the possibility of being heard by the human ear can be further reduced to improve the safety of recording shielding. Further, the second noise signal is random noise. The difference frequency signal (the difference frequency signal between the first noise signal and the second noise signal, the difference frequency signal between two different second noise signals) also includes at least random noise. Since random noise is difficult to crack, once the random noise is recorded into the recording device, the difficulty of the recording device to restore the protected audio signal is further increased, thereby further improving the reliability of preventing illegal recording.

[0081] The modulation unit 632 is used to modulate the input signal, such as addition, subtraction, multiplication, etc., which can be set according to actual needs. In this embodiment, the modulation unit 632 is taken as a mixer for example. The driving unit 633 is used to drive the probe unit 634 to work, and the signal output by the modulation unit 632 can be amplified. The driving unit 633 includes, for example, an operational amplifier and peripheral circuits to achieve power amplification. The probe unit 634 includes an ultrasonic probe, which can convert electrical energy into ultrasonic waves, such as a piezoelectric transducer.

[0082] In each signal generation submodule 63, the modulation unit 632 is connected to the noise unit 631, and the noise unit 631 is used to generate a second noise signal. The modulation unit 632 is used to receive the second noise signal sent by the noise unit 631 and the frequency signal sent by the signal source 1, and modulate the frequency signal and the second noise signal to obtain a second modulation signal.

[0083] In each signal generating submodule 63, the input end of the driving unit 633 is connected to the modulation unit 632, and the output end of the driving unit 633 is connected to the probe unit 634. The driving unit 633 is used to generate a third driving signal according to the second modulation signal, and send the third driving signal to the probe unit 634. The probe unit 634 sends a first ultrasonic wave to the receiving end.

[0084] There are two ways about the frequency bands of the first noise signal and the second noise signal. The first way is: the frequency difference between the first noise signal and at least one second noise signal overlaps with the entire frequency band or part of the frequency band of the protected audio signal. The second way is: the frequency band difference between each second noise signal and at least another second noise signal in all second noise signals overlaps with the entire frequency band or part of the frequency band of the protected audio signal. It should be noted that 1. Only the first way mentioned above is adopted; 2. Only the second way mentioned above is adopted; 3. Both the first way and the second way mentioned above are adopted. These three schemes are within the protection scope of this application.

[0085] The present embodiment is different from the above embodiment in that, although multiple ultrasonic waves are still sent simultaneously, each ultrasonic wave is superimposed with a noise signal, and the difference frequency signal finally reaching the receiving end is the difference frequency signal between different noise signals.

[0086] Application scenario 1: If the signal generating module 6 includes a signal generating submodule 63 (such as Figure 4 As shown), the frequency difference between the first noise signal and the second noise signal can be set to overlap the entire frequency band or part of the frequency band of the protected audio signal. The signal source 1 generates a frequency signal f0, and the first noise module 2 generates a first noise signal f N1 , the noise unit 631 generates a second noise signal f N2 The frequency signal f0 is respectively modulated by the first modulation module 3 and the modulation unit 632 corresponding to the first noise signal f N1 , the second noise signal f N2 The first modulation signal is converted by the first drive module 4 and the first probe module 5 to obtain the second ultrasonic wave f1=f0+f N1。 The second modulated signal is converted by the driving unit 633 and the probe unit 634 to obtain the first ultrasonic wave f2=f0+f N2 The first ultrasonic wave f2 and the second ultrasonic wave f1 generate a difference frequency signal f2-f1=f under the nonlinear effect of the propagation medium. N2 -f N1 , sum frequency signal f2+f1, etc. The high frequency signal is absorbed by the propagation medium, and the difference frequency signal f2-f1 is mainly left to the receiving end. Among them, the difference frequency signal f2-f1 is determined by the frequency band difference of the two noise signals. Since the frequency band difference of the two noise signals overlaps with the entire frequency band or part of the frequency band of the protected audio signal, it can also prevent the recording equipment from filtering out the difference frequency signal, thereby improving the reliability of recording shielding. If: f N1 The frequency range is 100 to 300 Hz, f N2The frequency band of the difference frequency signal f2-f1 is 200 to 500 Hz, and the frequency band of the protected audio signal is 300 to 3400 Hz. Therefore, the difference frequency signal overlaps part of the frequency band of the protected audio signal, thereby achieving recording shielding.

[0087] Application scenario 2 (not shown in the figure): If the signal generating module 6 includes two or more signal generating submodules 63, the noise units 631 in different signal generating submodules 63 can generate second noise signals of different frequency bands. In this scenario, each signal generating submodule 63 will eventually emit the first ultrasonic wave of the corresponding frequency band, and the first probe module 5 will also emit the second ultrasonic wave. Therefore, the second ultrasonic wave can generate a difference frequency signal with each first ultrasonic wave, and two different first ultrasonic waves will also generate a difference frequency signal. In this application scenario, the frequency band difference between the first noise signal and at least one of the second noise signals can overlap with the entire frequency band or part of the frequency band of the protected audio signal. Alternatively, it can also be that the frequency band difference between each second noise signal and at least another second noise signal overlaps with the entire frequency band or part of the frequency band of the protected audio signal. Alternatively, the above two conditions can also be met at the same time, that is, the frequency band difference between the first noise signal and at least one of the second noise signals overlaps with the entire frequency band or part of the frequency band of the protected audio signal, and the frequency band difference between each second noise signal and at least another second noise signal overlaps with the entire frequency band or part of the frequency band of the protected audio signal. No matter which of the above methods is adopted, it can be ensured that there will be a difference frequency signal overlapping with the entire frequency band or a part of the frequency band of the protected audio signal.

[0088] In summary, in this embodiment, based on the frequency signal and the second noise signal, a first ultrasonic wave modulated with the second noise signal can be obtained. Based on the frequency signal and the first noise signal, a first ultrasonic wave modulated with the first noise signal can be obtained. In the process of propagation of each of the first ultrasonic wave and the second ultrasonic wave, a difference frequency signal overlapping with part or all of the frequency band of the protected audio signal will be generated. Since the difference frequency signal overlaps with the frequency band of the protected audio signal, it can prevent the recording device from filtering out the difference frequency signal, thereby improving the reliability of recording shielding. And since the frequency of the difference frequency signal can be changed, it can also avoid the problem of harsh noise caused by the fixed frequency of the ultrasonic wave in the traditional scheme, so that the recording shielding operation is not easily noticed by the user.

[0089] Figure 5 The corresponding embodiments and Figure 4 The corresponding embodiments are similar. Figure 4 On the basis of the corresponding embodiment, one more transmission path may be added to transmit the third ultrasonic wave f0. Figure 5In another embodiment of a noise generating circuit of the present application, the signal generating module 6 further includes: a driving submodule 61 and a probe submodule 62 .

[0090] The input end of the driving submodule 61 is connected to the signal source 1, and the output end of the driving submodule 61 is connected to the probe submodule 62. The driving submodule 61 is used to generate a fourth driving signal according to the frequency signal, and send the fourth driving signal to the probe submodule 62. The probe submodule 62 sends a third ultrasonic wave to the receiving end according to the fourth driving signal, so that the first ultrasonic wave, the second ultrasonic wave and the third ultrasonic wave generate a difference frequency signal that overlaps with part or all of the frequency band of the protected audio signal. Among them, the frequency bands of the first noise signal and the second noise signal overlap with the frequency band of the protected audio signal.

[0091] Figure 5 The working principle of the corresponding embodiment is Figure 4 The working principle of the corresponding embodiment is similar, except that the newly added transmission path can propagate the ultrasonic wave f0, so that the ultrasonic waves f0, f1 and f2 generate difference frequency signals under the nonlinear effect of the propagation medium, and the difference frequency signals can shield the protected audio signal. In this embodiment, both the original ultrasonic wave (i.e., the third ultrasonic wave) and the ultrasonic wave modulated with noise (i.e., the first ultrasonic wave and the second ultrasonic wave) are emitted at the same time. During the propagation of these ultrasonic waves, any two ultrasonic waves with different frequency bands can generate difference frequency signals. As long as there is at least a partial overlap between the difference frequency signal and the frequency band of the protected audio signal, the recording device can be prevented from filtering out the difference frequency signal, thereby improving the shielding effect. Moreover, the more difference frequency signals there are, the better the effect of recording shielding.

[0092] The noise generation method of the present application is described below. It should be noted that in the noise generation method of the following embodiments, different steps can be performed by different devices, or all steps can be performed by the same chip or device. Figure 6 , an embodiment of the noise generation method of the present application includes the following contents.

[0093] 601. Generate a frequency signal of a preset frequency.

[0094] The protected audio signal is the sensitive sound information that the user needs to protect. For example, the frequency band of the protected audio signal is 300 to 3400 Hz, which is not limited here. The frequency of the frequency signal is also set according to actual needs, which is not limited here. The frequency of the frequency signal can be any value between 25 kHz and 40 kHz. The specific principle of this step can be the same as the working principle of the above-mentioned signal source 1, which will not be repeated here.

[0095] 602. Process the frequency signal to obtain at least one first ultrasonic wave.

[0096] The frequency signal is processed to obtain at least one first ultrasonic wave. Specifically, the frequency signal can be power amplified based on the hardware configuration, or mixed frequency modulation can be performed first and then power amplified to obtain the first ultrasonic wave. The hardware configuration can be set according to actual needs to select different processing methods, which are not limited here. For example, the generation principle of the first ultrasonic wave in the above embodiment can be referred to.

[0097] 603. Generate a first noise signal based on a preset rule.

[0098] Based on the preset rules, the first noise signal is generated. The preset rules are used to generate the first noise signal, such as whether it is random, whether it must be within a certain bandwidth value range, whether it must be a specific waveform, etc., which can be set according to actual needs to generate the corresponding first noise signal, and the specific principles are not limited here. For example, refer to the working principle of the first noise module 2 mentioned above.

[0099] 604. Modulate the first noise signal and the frequency signal to obtain a first modulated signal, and generate a second ultrasonic wave according to the first modulated signal.

[0100] The first noise signal and the frequency signal are modulated to obtain a first modulated signal, and a second ultrasonic wave is generated according to the first modulated signal. Specifically, the modulation may be mixing the first noise signal with the frequency signal, or other methods, which are not limited here. After obtaining the first modulated signal, the first modulated signal is specifically converted to obtain a corresponding second ultrasonic wave, wherein the conversion rule is also based on the hardware configuration and can be set according to actual needs. For example, the specific principle refers to the generation principle of the second ultrasonic wave in the above-mentioned noise generating circuit.

[0101] 605. Send the second ultrasonic wave and the first ultrasonic wave to the receiving end to generate a difference frequency signal overlapping a part of the frequency band or the whole frequency band of the protected audio signal.

[0102] The second ultrasonic wave and the first ultrasonic wave are sent to the receiving end to generate a difference frequency signal that overlaps part of the frequency band or the entire frequency band of the protected audio signal. During the propagation of the first ultrasonic wave and the second ultrasonic wave in the propagation medium, a difference frequency signal, a sum frequency signal, and a high-order harmonic signal of the first ultrasonic wave and the second ultrasonic wave are generated based on the nonlinear effect. Among them, the frequency band of the difference frequency signal can overlap part of or the entire frequency band of the protected audio signal. For the specific principle, reference can be made to the relevant principle of the difference frequency signal of the first ultrasonic wave and the second ultrasonic wave in the above-mentioned embodiment.

[0103] In the embodiment of the present application, a frequency signal of a preset frequency is first generated, and then the frequency signal is processed to send at least one first ultrasonic wave to the receiving end. At the same time, based on a preset rule, a first noise signal is generated, and then the first noise signal and the frequency signal are modulated to obtain a first modulated signal, and a second ultrasonic wave is generated according to the first modulated signal. The noise generation method sends the second ultrasonic wave and the first ultrasonic wave to the receiving end to generate a difference frequency signal overlapping with part or all of the frequency band of the protected audio signal. Due to the nonlinear acoustic effect of the propagation medium, a difference frequency signal overlapping with part or all of the frequency band of the protected audio signal will be generated during the propagation of the first ultrasonic wave and the second ultrasonic wave. Since the difference frequency signal overlaps with the frequency band of the protected audio signal, it can prevent the recording device from filtering out the difference frequency signal, thereby improving the reliability of recording shielding. And because the second ultrasonic wave is based on the first noise signal and the first ultrasonic wave is based on the frequency signal, the frequencies of the two ultrasonic waves are different, which makes the recording shielding operation not easy to be noticed by the user.

[0104] See also Figure 7 and Figure 8 Another embodiment of a noise generation method of the present application includes the following contents.

[0105] 701. Generate a frequency signal of a preset frequency.

[0106] The protected audio signal is the sensitive sound information that the user needs to shield. Usually, the frequency band of the protected audio signal is 300 to 3400 Hz, which is not limited here. The frequency of the frequency signal is also set according to actual needs, which is not limited here.

[0107] 702. Convert the frequency signal into a corresponding second driving signal based on a preset conversion rule.

[0108] The frequency signal is converted into a corresponding second drive signal based on a preset conversion rule. Specifically, the corresponding hardware configuration can be set according to actual needs as a premise of the preset conversion rule. The preset conversion rule is not specifically limited here. The second drive signal is used to drive the corresponding device to generate a subsequent signal.

[0109] 703. Generate a first ultrasonic wave corresponding to the second driving signal.

[0110] A first ultrasonic wave corresponding to the second driving signal is generated, wherein the frequency band of the first ultrasonic wave is the same as that of the frequency signal. Specifically, the first driving signal is converted to obtain a first ultrasonic wave having the same frequency band as that of the frequency signal. For example, the specific principle is referred to the working principle of the driving submodule 61 and the probe submodule 62 described above.

[0111] 704. Generate a first noise signal based on a preset rule.

[0112] The principle of 603 above may be referred to and will not be described in detail here.

[0113] 705. Modulate the first noise signal and the frequency signal to obtain a first modulated signal, and generate a second ultrasonic wave according to the first modulated signal.

[0114] The principle of 604 above may be referred to and will not be described in detail here.

[0115] 706. Send the second ultrasonic wave and the first ultrasonic wave to the receiving end to generate a difference frequency signal overlapping a part of the frequency band or the whole frequency band of the protected audio signal.

[0116] The second ultrasonic wave and the first ultrasonic wave are sent to the receiving end to generate a difference frequency signal that overlaps part of the frequency band or the whole frequency band of the protected audio signal. When the first ultrasonic wave and the second ultrasonic wave propagate in the propagation medium to the receiving end, nonlinear effects will be generated. Figure 8 The difference frequency signal f2-f1, sum frequency signal f1+f2 and higher harmonic signals of the first ultrasonic wave f1 and the second ultrasonic wave f2 generated by the nonlinear effect are mainly left with the difference frequency signal f2-f1 after being absorbed by the propagation medium (mainly absorbing high-frequency signals). The specific principle can be referred to above Figure 3 The embodiment shown.

[0117] In this embodiment, a frequency signal of a preset frequency is first generated, and then the frequency signal is processed to send at least one first ultrasonic wave to the receiving end. At the same time, based on a preset rule, a first noise signal is generated, and then the first noise signal and the frequency signal are modulated to obtain a first modulated signal, and a second ultrasonic wave is generated according to the first modulated signal, and finally the second ultrasonic wave and the first ultrasonic wave are sent to the receiving end to generate a difference frequency signal overlapping with part or all of the frequency band of the protected audio signal. Due to the nonlinear acoustic effect of the propagation medium, a difference frequency signal overlapping with part or all of the frequency band of the protected audio signal will be generated during the propagation of the first ultrasonic wave and the second ultrasonic wave. Since the difference frequency signal overlaps with the frequency band of the protected audio signal, it can prevent the recording device from filtering out the difference frequency signal, thereby improving the reliability of recording shielding. And because the frequency of the difference frequency signal can be changed, it can also avoid the problem of harsh noise caused by the fixed frequency of the ultrasonic wave in the traditional scheme, so that the recording shielding operation is not easy to be noticed by the user.

[0118] See also Fig. 9 and Fig.10 Another embodiment of a noise generation method of the present application includes the following contents.

[0119] 901. Generate a frequency signal of a preset frequency.

[0120] Step 901 in this embodiment is similar to steps 601 and 701 in the aforementioned embodiments, and will not be described in detail here.

[0121] 902. Generate at least one second noise signal.

[0122] Generate at least one second noise signal. The preset rules are used to indicate how to generate the second noise signal, whether it is random, whether it must be within a certain bandwidth value range, whether it must be a specific waveform, etc., which can be set according to actual needs to generate the corresponding second noise signal, and the specific principles are not limited here. The specific working principle of the noise unit 631 in the above-mentioned noise generating circuit can be referred to.

[0123] 903. Perform modulation processing on each second noise signal and the frequency signal respectively to obtain a second modulation signal corresponding to the second noise signal.

[0124] Each second noise signal is modulated with the frequency signal to obtain a second modulation signal corresponding to the second noise signal. The modulation process can be mixing and adding, or other methods, which are not specifically limited here. This embodiment is described by mixing and adding, and the second noise signal is mixed and added with the frequency signal to obtain the corresponding second modulation signal. The specific principle can refer to the specific working principle of the modulation unit 632 in the above-mentioned noise generating circuit.

[0125] 904. Convert the second modulation signal into a corresponding third driving signal based on a preset conversion rule.

[0126] The second modulation signal is converted into a corresponding third drive signal based on a preset conversion rule. Specifically, the corresponding hardware configuration can be set according to actual needs as a prerequisite for the preset conversion rule. The preset conversion rule is not specifically limited here. The third drive signal is used to drive the corresponding device to generate a subsequent signal. The specific principle can refer to the specific working principle of the driving unit 633 in the above-mentioned noise generating circuit.

[0127] 905. Generate a first ultrasonic wave corresponding to the third driving signal.

[0128] Generate a first ultrasonic wave corresponding to the third driving signal. The frequency band of the first ultrasonic wave is determined by the aforementioned signal. Specifically, the third driving signal is converted to obtain the corresponding first ultrasonic wave. The specific principle can refer to the specific working principle of the probe unit 634 in the above-mentioned noise generating circuit.

[0129] 906. Generate a first noise signal based on a preset rule.

[0130] Please refer to the content of step 603 above, which will not be repeated here.

[0131] 907. Modulate the first noise signal and the frequency signal to obtain a first modulated signal, and generate a second ultrasonic wave according to the first modulated signal.

[0132] Step 907 in this embodiment is similar to steps 604 and 705 in the above-mentioned embodiments, and will not be described again here.

[0133] 908. Send the second ultrasonic wave and the first ultrasonic wave to the receiving end to generate a difference frequency signal overlapping a part of the frequency band or the whole frequency band of the protected audio signal.

[0134] The second ultrasonic wave and the first ultrasonic wave are sent to the receiving end to generate a difference frequency signal overlapping with a part of the frequency band or the whole frequency band of the protected audio signal. The frequency difference between the first noise signal and at least one second noise signal overlaps with the whole frequency band or the whole frequency band of the protected audio signal; and / or the frequency difference between each second noise signal and at least another second noise signal in all the second noise signals overlaps with the whole frequency band or the whole frequency band of the protected audio signal. Fig.10 The difference frequency signal f generated by the nonlinear effect between the first ultrasonic wave f2 and the second ultrasonic wave f1 is N2 -f N1 , and frequency signal 2f0+f N1 +f N2 , and high-frequency signals. Since high-frequency signals are easily absorbed, the difference frequency signal f is mainly left. N2 -f N1 , realize recording shielding.

[0135] This embodiment is different from the above Figure 4 The principles of the illustrated embodiments are similar and will not be described in detail here.

[0136] exist Fig. 9 An ultrasonic wave is added to the embodiment shown to improve the shielding efficiency. Fig.11 Another embodiment of a noise generation method of the present application includes the following contents.

[0137] 1101. Generate a frequency signal of a preset frequency.

[0138] 1102. Generate at least one second noise signal.

[0139] 1103. Perform modulation processing on each second noise signal and the frequency signal respectively to obtain a second modulation signal corresponding to the second noise signal.

[0140] 1104. Convert the second modulation signal into a corresponding third driving signal based on a preset conversion rule.

[0141] 1105. Generate a first ultrasonic wave corresponding to the third driving signal.

[0142] 1106. Generate a first noise signal based on a preset rule.

[0143] 1107. Modulate the first noise signal and the frequency signal to obtain a first modulated signal, and generate a second ultrasonic wave according to the first modulated signal.

[0144] Steps 1001 to 1007 in this embodiment are similar to those in the previous Fig. 9 Steps 901 to 907 in the illustrated embodiment are similar and will not be described in detail here.

[0145] 1108. Convert the frequency signal into a corresponding fourth driving signal based on a preset conversion rule.

[0146] The frequency signal is converted into a corresponding fourth drive signal based on a preset conversion rule. Specifically, the corresponding hardware configuration can be set according to actual needs as a prerequisite for the preset conversion rule. The preset conversion rule is not specifically limited here. The fourth drive signal is used to drive the corresponding device to generate a subsequent signal. The specific principle can refer to the working principle of the above-mentioned driver submodule 61.

[0147] 1109. Generate a third ultrasonic wave corresponding to the fourth driving signal.

[0148] Generate a third ultrasonic wave corresponding to the fourth driving signal. The frequency band of the third ultrasonic wave is the same as that of the frequency signal. Specifically, the fourth driving signal is converted to obtain a third ultrasonic wave having the same frequency band as that of the frequency signal. The specific principle can refer to the working principle of the above-mentioned probe submodule 62.

[0149] 1110. Send a third ultrasonic wave, a second ultrasonic wave, and a first ultrasonic wave to a receiving end to generate a difference frequency signal that overlaps a part of or all of a frequency band of the protected audio signal.

[0150] The third ultrasonic wave, the second ultrasonic wave and the first ultrasonic wave are sent to the receiving end to generate a difference frequency signal overlapping with a part of the frequency band or the whole frequency band of the protected audio signal. The frequency band difference of any two noise signals in all noise signals may overlap with the frequency band of the protected audio signal, and all noise signals include the first noise signal and the second noise signal. Figure 5 The principles shown are similar and will not be repeated here.

[0151] An embodiment of the present application further provides a recording shielding device, including the noise generating circuit as described above. A person skilled in the art can clearly understand that for the convenience and simplicity of description, the specific working process of the recording shielding device described above can refer to the corresponding content in the aforementioned embodiment, and will not be repeated here.

[0152] It should be noted that, although the steps in the flowcharts involved in the embodiments are drawn in sequence according to the instructions of the arrows, unless otherwise clearly stated in this document, there is no strict order restriction on the execution of these steps, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the embodiments may include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0153] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0154] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0155] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0156] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the various embodiments of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, read-only memory), random access memory (RAM, random access memory), disk or optical disk, etc. Various media that can store program codes.

Claims

1. A noise generating circuit, characterized in that: include: A signal source, a first noise module, a first modulation module, a first driving module, a first probe module and a signal generation module; The signal source is connected to the signal generating module and the first modulation module respectively, and the signal source is used to generate a frequency signal of a preset frequency; The signal generating module is used to send at least one first ultrasonic wave to the receiving end according to the frequency signal; The first modulation module is connected to the first noise module, and the first modulation module is used to receive the first noise signal generated by the first noise module, and modulate the first noise signal and the frequency signal received from the signal source to obtain a first modulation signal; The first driving module is respectively connected to the first modulation module and the first probe module, and the first driving module is used to generate a first driving signal based on the first modulation signal, and send the first driving signal to the first probe module; the first probe module sends a second ultrasonic wave based on the first driving signal to generate a difference frequency signal with the first ultrasonic wave that overlaps with part or all of the frequency band of the protected audio signal.

2. The noise generating circuit according to claim 1, characterized in that: The signal generation module includes: a driving submodule and a probe submodule; The input end of the driving submodule is connected to the signal source, and the output end of the driving submodule is connected to the probe submodule. The driving submodule is used to generate a second driving signal according to the frequency signal and send the second driving signal to the probe submodule; the probe submodule sends one of the first ultrasonic waves to the receiving end, wherein the frequency band of the first ultrasonic wave is the same as that of the frequency signal, and the frequency band of the first noise signal overlaps with part or all of the frequency band of the protected audio signal.

3. The noise generating circuit according to claim 1, characterized in that: The signal generation module includes at least one signal generation submodule, each of which includes: a noise unit, a modulation unit, a driving unit and a probe unit, and the modulation unit of each signal generation submodule is connected to the signal source; In each of the signal generating submodules, the modulation unit is connected to the noise unit, the noise unit is used to generate a second noise signal, the modulation unit is used to receive the second noise signal sent by the noise unit and the frequency signal sent by the signal source, and modulate the frequency signal and the second noise signal to obtain a second modulation signal; In each of the signal generating submodules, the input end of the driving unit is connected to the modulation unit, the output end of the driving unit is connected to the probe unit, the driving unit is used to generate a third driving signal according to the second modulation signal, and send the third driving signal to the probe unit; the probe unit sends one of the first ultrasonic waves to the receiving end; The frequency difference between the first noise signal and at least one of the second noise signals overlaps with the entire frequency band or part of the frequency band of the protected audio signal; and / or the frequency band difference between each of the second noise signals and at least another second noise signal in all the second noise signals overlaps with the entire frequency band or part of the frequency band of the protected audio signal.

4. The noise generating circuit according to claim 3, characterized in that: The signal generation module also includes: a driving submodule and a probe submodule; The input end of the driving submodule is connected to the signal source, and the output end of the driving submodule is connected to the probe submodule. The driving submodule is used to generate a fourth driving signal according to the frequency signal and send the fourth driving signal to the probe submodule; the probe submodule sends a third ultrasonic wave to the receiving end according to the fourth driving signal, so that the first ultrasonic wave, the second ultrasonic wave and the third ultrasonic wave generate a difference frequency signal that overlaps with part or all of the frequency band of the protected audio signal.

5. The noise generating circuit according to claim 1, characterized in that: The first noise signal has a preset frequency bandwidth.

6. The noise generating circuit according to claim 1, characterized in that: The first noise signal is a random signal.

7. The noise generating circuit according to claim 1, characterized in that: The frequency of the frequency signal is greater than or equal to 25 kHz and less than or equal to 40 kHz.

8. A noise generating method, characterized in that: include: Generate a frequency signal of a preset frequency; Processing the frequency signal to obtain at least one first ultrasonic wave; Based on a preset rule, generating a first noise signal; Modulating the first noise signal and the frequency signal to obtain a first modulated signal, and generating a second ultrasonic wave according to the first modulated signal; The second ultrasonic wave and the first ultrasonic wave are sent to a receiving end to generate a difference frequency signal overlapping a part of or the whole frequency band of the protected audio signal.

9. The noise generating method according to claim 8, characterized in that: The processing of the frequency signal to obtain at least one first ultrasonic wave comprises: Converting the frequency signal into a corresponding second driving signal based on a preset conversion rule; generating one of the first ultrasonic waves corresponding to the second driving signal; The frequency band of the first ultrasonic wave is the same as that of the frequency signal, and the frequency band of the first noise signal overlaps with the frequency band of the protected audio signal.

10. The noise generating method according to claim 8, characterized in that: Before processing the frequency signal to obtain at least one first ultrasonic wave, the method further includes: generating at least one second noise signal; The processing of the frequency signal to obtain at least one first ultrasonic wave comprises: Performing modulation processing on each of the second noise signals and the frequency signal respectively to obtain a second modulation signal corresponding to the second noise signal; Converting the second modulation signal into a corresponding third drive signal based on a preset conversion rule; generating the first ultrasonic wave corresponding to the third driving signal; The frequency difference between the first noise signal and at least one of the second noise signals overlaps with the entire frequency band or part of the frequency band of the protected audio signal; and / or the frequency band difference between each of the second noise signals and at least another second noise signal in all the second noise signals overlaps with the entire frequency band or part of the frequency band of the protected audio signal.

11. The noise generating method according to claim 10, characterized in that: The method further comprises: Converting the frequency signal into a corresponding fourth driving signal based on a preset conversion rule; generating a third ultrasonic wave corresponding to the fourth driving signal; The sending the second ultrasonic wave and the first ultrasonic wave to the receiving end to generate a difference frequency signal overlapping a part of the frequency band or the whole frequency band of the protected audio signal includes: The third ultrasonic wave, the second ultrasonic wave and the first ultrasonic wave are sent to a receiving end to generate a difference frequency signal overlapping a part of the frequency band or the whole frequency band of the protected audio signal.

12. A recording shielding device, characterized in that: Comprising the noise generating circuit as claimed in any one of claims 1 to 7.

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