Programmable parametric array loudspeaker with safety device

Abstract

The present invention discloses a programmable parametric array speaker with a safety device, which belongs to the field of parametric array engineering applications. The device includes an audio acquisition module, a signal processing module, a parametric array speaker array and a microphone volume detection module, wherein the audio acquisition module collects audio as a digital signal, the signal processing module uses a programmable chip to modulate the digital signal, post-processes the digital signal, and modulates the audio signal onto an ultrasonic carrier, the parametric array speaker array emits ultrasonic waves into the air and self-demodulates audible audio, and people will reflect the audio part to the microphone while hearing the audio, and the microphone volume detection module can detect the amplitude of the audio and the distance from the person to the parametric array to adjust the emission intensity of the parametric array speaker array. The present invention adjusts the emission power of the parametric array through a volume safety device, thereby ensuring the safety of people when they are close to the parametric array and avoiding hearing damage.

Description

Technical Field

[0001] The invention belongs to the field of parametric array engineering applications, and in particular relates to a programmable parametric array loudspeaker with a safety device. Background Art

[0002] The sound waves emitted by traditional speakers are not directional or have weak directionality. The ultrasonic transducer in the parametric array emits two ultrasonic carriers and sideband signals with similar frequencies and have strong directionality. Therefore, the audio signal is modulated onto the ultrasonic carrier and emitted into the air through the ultrasonic transducer. Ultrasound propagates in the air, and the nonlinear effect of the air is used to generate high-order harmonics, sum frequencies, and difference frequencies during the propagation process. The only audible one is the difference frequency. The difference frequency generated by the modulation method is the original audio signal, which inherits the strong directionality of ultrasound, that is, the directionally propagated audio signal.

[0003] In actual applications, such as the patent applications with application number 202010636697.7 and application name “A scalable, beam-controllable directional sound wave transmitting device”; and application number 202010636455.8 and application name “Fixed-point sound wave transmitting device based on parametric array principle”, directional audio transmission technology with controllable area based on parametric array is disclosed. The audio generated by the parametric array can allow the listener to hear the sound without affecting the people around, thereby reducing the generation of noise. Although the current scheme can use the parametric array principle to generate controllable directional audio, the sound pressure level of the sound waves emitted by the parametric array is greater than that of conventional speakers, so excessive volume may damage the listener's hearing. Integrating a volume safety device into the parametric array speaker has become a technical problem that needs to be solved, and the parametric array signal processing part of the existing scheme is mostly completed using digital integrated chips and analog chips, which is not convenient for upgrading the technology without changing the hardware. Summary of the invention

[0004] The purpose of the invention is that the current parametric array directional audio transmission technology can only control the direction, quantity and distance of the sound waves, but cannot control the volume of the sound waves. The present invention provides a safety device for the directional propagation of audio by the parametric array, which can adjust the output amplitude of the parametric array according to the distance from the person to the parametric array and the intensity of the reflected audio, protect the listener from being exposed to high-intensity sound pressure levels, reduce the risk of hearing damage, and use a programmable device to replace the digital integrated chip and the analog chip in the existing parametric array system, thereby increasing the stability of the system and facilitating subsequent iterative updates.

[0005] The programmable parametric array speaker with a safety device provided by the present invention comprises an audio acquisition module, a signal processing module, a parametric array speaker array and a microphone volume detection module;

[0006] The audio acquisition module includes an analog-to-digital converter and an audio interface. The audio signal to be transmitted is connected to the analog-to-digital converter through the audio interface to convert it into a digital signal. The output end of the audio acquisition module is connected to the input end of the signal processing module.

[0007] The signal processing module includes a programmable device, receives the digital signal input from the audio acquisition module, performs modulation operation and post-processing operation in the module based on the programmable device, wherein the modulation operation modulates the audio signal to the resonant frequency and bandwidth of the ultrasonic transducer, and the post-processing operation matches the output form of the ultrasonic signal output by the modulation operation with the input form of the subsequent power amplifier; the output end of the signal processing module is connected to the input end of the parametric array speaker array;

[0008] The parametric array speaker array includes a plurality of ultrasonic transducers forming an array and a power amplifier matched therewith. The front end of the parametric array speaker array is a power amplifier, and the back end is an ultrasonic transducer. The parametric array speaker array is used to transmit ultrasonic signals carrying audio information into the air, and restore audible audio signals through air self-demodulation;

[0009] The microphone volume detection module includes a microphone, an analog-to-digital converter and an audio detector. The microphone (the operating frequency must include the range audible to the human ear) receives the audio signal of the transmitted audio of the parametric array speaker array after being reflected by the human body, which is sampled into a digital signal by the analog-to-digital converter. The audio detector then detects the intensity of the audio signal reflected by the human body, and controls the output amplitude of the parametric array speaker array based on the intensity of the audio signal.

[0010] Furthermore, the audio detector of the microphone volume detection module detects the intensity of the audio signal reflected by the human body by using a programmable device to detect the correlation between the signal collected by the microphone and the emitted audio, and calculates the amplitude and time difference of the reflected audio (the audio signal reflected by the human body), thereby controlling the output amplitude of the parametric array speaker array.

[0011] Furthermore, the modulation modes of the modulation operation of the signal processing module include but are not limited to: double sideband, single sideband, square root, improved amplitude; the modulation operation modulates the preprocessed signal into a form that matches the power amplifier in the parametric array speaker array, such as an analog signal or a single-bit signal.

[0012] Furthermore, the multiple ultrasonic transducers of the parametric array speaker array have the same resonant frequency and the same bandwidth, and the multiple ultrasonic transducers are coaxially arranged, and the operating frequency range of each power amplifier of the parametric array speaker array matches the ultrasonic transducer.

[0013] Furthermore, the signal processing module and the audio detector both include a programmable device, and the signal processing can be performed by the same programmable device or by different programmable devices.

[0014] Furthermore, the programmable device is implemented using a field programmable gate array and can be subsequently upgraded or replaced with other types of programmable chips.

[0015] In summary, due to the adoption of the above technical solution, the effective gain of the present invention is:

[0016] (1) It has a variety of selectable modulation and post-processing methods, making the device more universal;

[0017] (2) It has a volume safety device that calculates the distance between the person and the parametric array and the amplitude of the reflected sound wave through matching filtering and constant false alarm detection, and adjusts the output amplitude of the parametric array speaker array to protect the listener's hearing safety;

[0018] (3) The field programmable logic gate array is used to implement operations such as modulation, post-processing and audio detection, which facilitates subsequent improvement, upgrade and large-scale deployment of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 The present invention is a system implementation block diagram of a programmable parametric array speaker with a safety device in a specific implementation manner.

[0021] Figure 2 This is a schematic diagram of a signal processing module in a specific implementation manner.

[0022] Figure 3 Schematic diagram of a parametric array loudspeaker array in a specific implementation manner.

[0023] Figure 4 It is a schematic diagram of the nonlinear effect of the parametric array in a specific implementation manner.

[0024] Figure 5 Schematic diagram of a microphone volume detection module in a specific implementation manner.

[0025] Figure 6 It is a diagram of simulation results of an audio detector in a microphone volume detection module in a specific implementation manner. DETAILED DESCRIPTION

[0026] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0027] The present invention provides a parametric array safety device, which is suitable for detecting the position of the listener from the parametric array and the intensity of the reflected sound wave when the parametric array is used to transmit directional audio, so as to adjust the transmission power of the parametric array, and ensure the safety of the listener within the directional audio propagation range without interfering with the normal operation of the parametric array. The present invention uses an analog-to-digital converter to convert the audio into a digital signal at the input end, and uses a digital-to-analog converter to convert the digital signal into an ultrasonic signal at the output end, which is directly output by a power amplifier and an ultrasonic transducer. Modulation, post-processing, audio detection and other operations are all processed by a field programmable logic gate array. Compared with analog devices, this solution is small in size, high in stability, easy to upgrade, and easy to deploy in large quantities.

[0028] The programmable parametric array speaker with a safety device of the present invention comprises: an audio acquisition module, a signal processing module, a parametric array speaker array, and a microphone volume detection module;

[0029] The audio acquisition module uses the headphone interface to input the audio of the external device and converts it into digital signal audio through the analog-to-digital converter, and then transmits the digital signal audio to the signal processing module. The external device can select the pre-recorded audio in the memory card, the audio played by the mobile phone, or the real-time audio input from the microphone;

[0030] The signal processing module uses a programmable device (such as a programmable chip) to read the digital signal audio and perform modulation, post-processing and other operations, modulate the audio onto the ultrasonic carrier, and then use a post-processing method to match the output form of the modulated ultrasonic signal with the input form of the subsequent power amplifier;

[0031] The most common modulation methods in the signal processing module are double-sideband modulation, single-sideband modulation, square root modulation and improved amplitude modulation. Different modulation methods have different degrees of suppression of total harmonic distortion, and different modulation methods have different requirements for the output bandwidth of the ultrasonic transducer. Therefore, the appropriate modulation method should be selected according to the actual required indicators of the system;

[0032] The modulation method uses a programmable chip to generate a high-frequency carrier signal, and the modulated ultrasonic signal should contain a carrier and at least one sideband signal, and the difference between the frequency of the sideband signal and the frequency of the carrier signal is the frequency of the original audio signal, so that the audio signal can be restored by utilizing the nonlinear effect of air;

[0033] The post-processing method in the signal processing module is selected according to the power amplifier of the parametric array speaker array. If it is a class D power amplifier, pulse density modulation is used to convert the modulated signal into a single-bit form; if it is a class A, B, or AB power amplifier, a digital-to-analog converter is used to convert the modulated signal into an analog signal to match the input form of the power amplifier;

[0034] The front end of the parametric array speaker array is a power amplifier, which receives the ultrasonic signal after modulation and post-processing. The operating frequency range of the power amplifier, the resonant frequency of the ultrasonic transducer and the modulation carrier frequency match each other. The bandwidth of the power amplifier, the bandwidth of the ultrasonic transducer and the audio bandwidth match each other. The ultrasonic transducer converts the power-amplified electrical signal into an ultrasonic signal and transmits it in the air. The modulated ultrasonic signal can self-demodulate the audio signal when propagating in the air. If a listener appears in the directional audio area, the sound can be heard and the human body will reflect part of the sound to the microphone.

[0035] The front end of the microphone volume detection module is a microphone, which can collect the audio signal reflected by the human body, convert it into a digital signal by the analog-to-digital converter, and then pass it to the programmable chip of the back-end audio detector to detect the reflected sound wave;

[0036] The audio detector of the microphone volume detection module uses a programmable chip to implement a matched filter to detect whether a reflected signal exists, obtain the maximum signal-to-noise ratio output, form a peak, and then use a constant false alarm detector to detect the position and size of the peak. The distance between the person and the parametric array can be calculated based on the position of the peak. The intensity of the reflected sound wave can be calculated based on the peak size to adjust the output amplitude of the parametric array speaker array.

[0037] There are two situations for adjusting the output amplitude of the parametric array speaker array. If no peak is detected, there is no need to adjust the output amplitude of the parametric array. If a peak is detected, the output amplitude of the parametric array is adjusted according to the rule that the output sound pressure of the parametric array is linear with the distance from the person to the parametric array.

[0038] As a possible implementation, Figure 1As shown, the parametric array safety device provided by the embodiment of the present invention uses an analog-to-digital converter to read an external audio file in real time, converts the audio into a digital signal, and hands it over to a signal processing module to modulate it into an ultrasonic signal, which is then post-processed to match the operating frequency range and bandwidth of the power amplifier. The ultrasonic transducer array transmits the ultrasonic signal carrying information into the air in a direction, and self-demodulates the audible audio through the nonlinear effect of the air. When a person hears the sound several meters away, part of the sound will also be reflected to the microphone. After the microphone receives the reflected sound, it is collected into the audio detector through the analog-to-digital converter, and a matched filter is used to detect whether the audio signal exists in the echo. Then, a constant false alarm detector is used to detect whether there is reflected audio and the time when the reflected audio appears. If there is reflected audio, the peak amplitude after matched filtering can be calculated, and the distance between the listener and the parametric array can be calculated based on the time difference to control the output amplitude of the parametric array, so that the parametric array effect can be used to generate directional audio, reduce the generation of noise, and also take into account the hearing safety of the listener.

[0039] External devices such as MP3, memory cards, mobile phones, etc. are connected to the audio interface of the present invention through audio cables, and the audio files played by the external devices will be transmitted in a directional manner. Since digital signals have stronger anti-interference ability than analog signals, are easier to process, and have higher device integration, the audio is first converted into a digital signal through an analog-to-digital converter and transmitted to the signal processing module.

[0040] according to Figure 2 The signal processing module first performs a modulation operation on the digital audio signal. The carrier generated inside the programmable chip is modulated to the ultrasonic frequency through any one of double-sideband modulation, single-sideband modulation, square root modulation and improved amplitude modulation. Then, according to the type of the subsequent power amplifier, a suitable post-processing method is selected. If it is a class D power amplifier, pulse density modulation should be used to process the ultrasonic signal into a single-bit signal. Using a single-bit signal has less hardware resource overhead and smaller size than using a digital-to-analog converter, and is more suitable for use in miniaturized equipment, but the system needs to work at a higher clock frequency; if it is a class A, B, or AB power amplifier, a digital-to-analog converter should be used to process the ultrasonic signal into an analog signal, which is easy to control noise, but will increase the size of the equipment.

[0041] Right now Figure 2The signal processing module shown includes a modulation unit and a post-processing unit, wherein a plurality of conventional modulation modes are configured in the modulation unit, and a modulation sub-unit corresponding to each modulation mode is connected to the post-processing unit at the back end through a selector, so that the modulation unit selects any one of the plurality of modulation modes configured, and the functions of different modulation sub-units are all implemented by programmable chips, and different modulation modes can be selected through programmable chips. After the current input audio signal is modulated and processed, it is input to the post-processing unit for post-processing, and the post-processing unit includes a pulse density modulation unit and a digital-to-analog converter, both of which are connected to the power amplifier of the parametric array speaker array at the back end through a selector, and the pulse density modulation unit or the digital-to-analog converter is connected based on the type of the power amplifier at the back end, and the specific selection can be realized through a programmable chip.

[0042] In the signal processing module, the modulation operation takes double-sideband modulation as an example. Assume that the input audio signal g(t) is a single-tone signal, that is, g(t) = sin(ω 1 t), where ω 1 is the audio frequency of the audio signal g(t), that is, the original audio frequency, then the double-sideband modulation method modulates the audio signal to f(t) = [1 + mg(t)]sin(ω 0 t), where m is the modulation coefficient, ω 0 is the frequency of the modulated carrier, the modulation envelope E(t) = 1 + mg(t), and the Berktay far-field model is used to describe the self-demodulation and restoration of audio in the air. The demodulated signal is: This formula contains the harmonic 2ω of the audio signal g(t) 1 , since m < 1, and high-order harmonics decay faster in the air, the ultrasonic signal can self-demodulate the audio signal after a certain propagation distance. Among them, β represents the nonlinear coefficient of air, p 0 represents the amplitude of the modulated carrier, α represents the acoustic absorption coefficient of the modulated carrier, ρ 0 represents the density of air, c 0 represents the speed of sound in the air, and z represents the distance from the observation point to the parametric array speaker array.

[0043] In the signal processing module, post-processing operations include pulse density modulation and digital-to-analog converter. Post-processing is to match the output form of the ultrasonic signal with the subsequent power amplifier. Pulse density modulation uses a higher sampling rate to quantize digital signals of different amplitudes into fast-changing single-bit signals. Its advantage is that it can be completed in a programmable chip; using a digital-to-analog converter does not require a very high sampling rate, and the quantization noise generated is related to the number of bits of the digital-to-analog converter.

[0044] according to Figure 3The front end of the parametric array speaker array is a power amplifier. If the system adopts a single-bit post-processing method, a class D power amplifier is used to compare the single-bit switching signal with a high-frequency triangle wave and then connect it to the power amplifier circuit. The class D power amplifier uses a metal oxide field effect transistor, so it is very efficient and generates very little heat; if the system adopts a digital-to-analog converter post-processing method, then class A, B, and AB power amplifiers can be used. Class A power amplifiers generate very high heat and have very little distortion, making them ideal high-fidelity power amplifiers. Class B amplifiers have the opposite characteristics to class A amplifiers, with high efficiency but large distortion. Class AB power amplifiers combine the advantages of class A and class B power amplifiers. The power amplifier is connected to the ultrasonic transducer array, which converts the input electrical power into ultrasonic waves and then transmits them out. In the programmable chip, algorithms such as beamforming and multi-beam can be performed on the array to flexibly control the directional audio area.

[0045] Figure 4 The principle of demodulating audio signals using the nonlinear effects of parametric arrays is described. When the parametric array emits two high-intensity main frequency ultrasonic beams with similar frequencies, secondary sound components of different frequencies are generated in the direction of the beam due to the nonlinear properties of the air, including sum frequency, difference frequency, and higher harmonics. However, the sum frequency and higher harmonics decay quickly in the air because of their high frequencies, and because the frequencies are higher than 20kHz, they are inaudible to humans. Only the difference frequency can be heard across a distance because of its small attenuation and within the audible frequency range of the human ear. Because the difference frequency is generated in the ultrasonic beam, there is no difference frequency without the ultrasonic beam, so the difference frequency inherits the high directivity of the ultrasonic wave. Therefore, the parametric array speaker can rely on the high directivity of the ultrasonic wave to generate a highly directional audio beam.

[0046] according to Figure 5 , Microphone volume detection module, uses a microphone to collect audio signals reflected from the human body. Since the parametric array self-demodulation requires a certain propagation distance, when the microphone is placed in the center of the parametric array, the microphone will only receive the reflected audio signal and will not receive the directly demodulated audio. Use an analog-to-digital converter to convert the reflected sound into a digital signal. In the application, audio with a duration of T can be intercepted and detected using the matched filtering method. According to the Berktay far-field model, the demodulated audio is negatively correlated with the original audio, so the filter h(t) = -g(Tt) is selected, where T is the total length of the audio signal. Assuming that the echo signal received by the microphone is s(t), the output of the matched filter is If a person appears in the audio propagation area of ​​the parametric array and the sound emitted by the parametric array is loud, a peak will appear in the output of the matched filter. The constant false alarm detector can be used to detect whether the reflected sound exists. If it does, the time when the reflection peak occurs is marked, thereby calculating the distance between the person and the parametric array, and combining the amplitude of the reflected audio to adjust the transmission amplitude of the parametric array.

[0047] The sound pressure range audible to the human ear is 0.00002Pa to 20Pa. Since the directional audio emitted by the parametric array is mixed with ultrasound, in order to ensure safety, the audible audio sound pressure within a close range should not be too high. The steps of controlling the volume of the present invention are as follows:

[0048] If the reflected audio peak cannot be detected, it means that the volume of the audio is already low when it reaches the person, and the person is far away from the parameter array. The energy of the ultrasonic frequency part has little impact on the person, and there is no need to adjust the volume.

[0049] Secondly, if the reflected audio peak can be detected, the safe volume is selected according to the rule that the sound pressure is linear with the distance, and the sound pressure threshold is selected as Pth, the distance corresponding to the sound pressure threshold is D, and the silent distance threshold is dth. That is, when the distance between the person and the parameter array is D, the peak sound pressure output by the parameter array is not higher than Pth; when the person is dth away from the parameter array, the parameter array does not output audio. In summary, Where l is the distance from the person to the parameter array, and P is the peak sound pressure output by the parameter array. The typical sound pressure threshold Pth = 20Pa, the distance corresponding to the sound pressure threshold D = 5 meters, and the silent distance threshold dth = 0.5 meters.

[0050] In order to demonstrate the effect of the programmable parametric array speaker with a safety device provided by an embodiment of the present invention, the sampling rate of the system is 4MHz, the array is composed of 40 coaxially arranged ultrasonic transducers, the output sound pressure peak is 20Pa, the microphone is placed in the center of the transducer array, the audio signal selects a 500Hz to 8000Hz linear frequency modulation signal to cover the typical parametric array sound frequency band, adopts a double-sideband modulation with a modulation coefficient of 0.9, and selects a carrier frequency of 40kHz, which is also a common resonant frequency of an ultrasonic transducer. A reflective surface of skin material is simulated at 3 meters to simulate a listener. A microphone is placed in the center of the parametric array to receive the reflected audio. The matched filter selects an audio with a duration of T=0.1 seconds for the constant false alarm detector. The false alarm probability P fa =10 -3 , Figure 6 The output of the microphone volume detection module after matched filtering and the results after constant false alarm detection are shown. The results show that the constant false alarm detector outputs a peak value at about the 470,000th sampling point, that is, the audio is delayed by about 0.0175 seconds to reach the microphone, and the distance is about 3 meters. Since an obvious peak is detected, the output sound pressure peak of the parametric array calculated according to the linear rule should be reduced to 11.1Pa.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0052] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the creative concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A programmable parametric array speaker with a safety device, comprising an audio acquisition module, a signal processing module, a parametric array speaker array, and a microphone volume detection module; The audio acquisition module includes an analog-to-digital converter and an audio interface. The audio signal to be transmitted is connected to the analog-to-digital converter through the audio interface to convert it into a digital signal. The output end of the audio acquisition module is connected to the input end of the signal processing module. The signal processing module includes a programmable device, receives the digital signal input from the audio acquisition module, performs modulation operation and post-processing operation in the module based on the programmable device, wherein the modulation operation modulates the audio signal to the resonant frequency and bandwidth of the ultrasonic transducer, and the post-processing operation matches the output form of the ultrasonic signal output by the modulation operation with the input form of the subsequent power amplifier; the output end of the signal processing module is connected to the input end of the parametric array speaker array; The parametric array speaker array includes a plurality of ultrasonic transducers forming an array and a power amplifier matched therewith. The front end of the parametric array speaker array is a power amplifier, and the back end is an ultrasonic transducer. The parametric array speaker array is used to transmit ultrasonic signals carrying audio information into the air, and restore audible audio signals through air self-demodulation; The microphone volume detection module includes a microphone, an analog-to-digital converter and an audio detector, wherein the microphone is placed at the center of the parametric array speaker array, and the microphone receives the audio signal of the transmitted audio of the parametric array speaker array after being reflected by the human body, which is sampled into a digital signal by the analog-to-digital converter, and then the audio detector detects the intensity of the audio signal reflected by the human body. The output amplitude of the parametric array speaker array is controlled based on the audio signal intensity detected by the audio detector, so as to protect the hearing safety of the listener, which specifically includes: Intercept the audio with a duration of T, select the filter h(t) = -g(Tt), where T is the total length of the audio signal, g(t) is the input audio signal, define the echo signal received by the microphone as s(t), and the output of the matched filter is If a person appears in the audio propagation area of ​​the parametric array and the sound emitted by the parametric array is loud, a peak will appear in the output of the matched filter. The constant false alarm detector can be used to detect whether the reflected sound exists. If it exists, the time when the reflection peak appears is marked, thereby calculating the distance between the person and the parametric array, and combining the amplitude of the reflected audio to adjust the transmission amplitude of the parametric array: The peak value of the audio signal reflected by the human body is detected. If no peak value can be detected, the output amplitude of the parametric array speaker array remains unchanged. If the peak value is detected, the safe volume is selected according to the rule that the sound pressure and the distance are linear, and the sound pressure threshold Pth, the distance D corresponding to the sound pressure threshold Pth, and the silent distance threshold dth are selected; the output sound pressure peak value P of the control parameter array speaker array is: Where l represents the distance from the human body to the parametric array speaker array.

2. The programmable parametric array loudspeaker with a safety device as claimed in claim 1, characterized in that: The output amplitude of the parametric array speaker array is controlled based on the audio signal strength detected by the audio detector. Specifically, a programmable device is used to detect the correlation between the signal collected by the microphone and the emitted audio, and the amplitude and time difference of the audio signal reflected by the human body are calculated, thereby controlling the output amplitude of the parametric array speaker array.

3. The programmable parametric array loudspeaker with a safety device as claimed in claim 2, characterized in that: Set the sound pressure threshold Pth = 20Pa, the distance corresponding to the sound pressure threshold D = 5 meters, and the silent distance threshold dth = 0.5 meters.

4. The programmable parametric array loudspeaker with a safety device according to any one of claims 1 to 3, characterized in that: The modulation modes of the modulation operation of the signal processing module include: double sideband, single sideband, square root, and improved amplitude.

5. The programmable parametric array loudspeaker with a safety device according to any one of claims 1 to 3, characterized in that: The multiple ultrasonic transducers of the parametric array loudspeaker array have the same resonant frequency and the same bandwidth, and the multiple ultrasonic transducers are coaxially arranged. The operating frequency range of each power amplifier of the parametric array loudspeaker array matches the ultrasonic transducer.

6. The programmable parametric array loudspeaker with a safety device according to any one of claims 1 to 3, characterized in that: The signal processing module and the audio detector both include programmable devices, and the signal processing can be performed by the same programmable device or by different programmable devices.

7. The programmable parametric array loudspeaker with a safety device according to any one of claims 1 to 3, characterized in that: The programmable device is implemented by using a field programmable logic gate array.

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