CN117854467A - Audio processing method and device suitable for hidden communication of active noise reduction system - Google Patents
Audio processing method and device suitable for hidden communication of active noise reduction system Download PDFInfo
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Abstract
The invention relates to an audio processing method and device suitable for hidden communication of an active noise reduction system, wherein the method comprises the following steps: acquiring original audio, and intercepting a pre-transmitted frequency band signal from the original audio; modulating the intercepted frequency band signals to mutually non-overlapping ultrasonic wave bands; combining the modulated audio into a combined audio; according to the position direction of the active noise reduction system and the frequency band distribution of the combined audio, calculating the phase delay of the audio sent by each array element in the phased array; compensating in the phase spectrum of the combined audio according to the calculated phase delay, and then sending out the compensated combined audio through a phased array; the active noise reduction system receives the combined audio, generates the original audio through the receiving circuit, combines the processing of the active noise reduction algorithm, and restores to obtain the sound signal. Compared with the prior art, the invention can shorten the response time of the communication system, simplify the structure of the communication system, and realize the purpose of remote and multi-angle concurrent hidden communication on the premise of low cost.
Description
Technical Field
The invention relates to the technical field of sound signal processing, in particular to an audio processing method and device suitable for hidden communication of an active noise reduction system.
Background
With the increase of the number of mobile intelligent devices, the hidden communication technology based on acoustic signals has also been greatly developed. In general, the bandwidth of the working frequency band of the sound equipment (such as sound card, speaker, microphone, etc.) in the information equipment is larger than the bandwidth of the audio frequency band accepted by the human ear, when a person selects the frequency band beyond the accepted range of the human ear or the special sound easily ignored by the person as the carrier wave, the information can be transmitted in a hidden manner, so that in numerous sound hidden communication technologies, using the ultrasonic signal as the transmission medium is the key point and hot point of the research of the person. The previous researches on the related aspects are based on the technologies of frequency modulation, amplitude modulation and the like in the communication engineering, so that the transmission of 0-1 signals is realized. The communication mode is unstable and has extremely low speed. In addition, the communication mode also needs a series of follow-up operations such as demodulating, decoding, audio playing and the like after the receiving end receives the signal, which causes the problems of complex system structure and long processing time.
In addition, with the rapid development of electronic technology and computer technology, ultrasonic phased array technology has been gradually applied to the fields of industrial nondestructive inspection and the like from the medical field. Speaker arrays are used as one of the simplest phased arrays in many applications, such as special-purpose audio, computer, television, etc., however, speaker arrays, especially ultrasonic speaker arrays, are rarely used, and the main direction of research is single-audio steering angle control, and in fact, since the single audio bandwidth is not very large, most of the bandwidth is wasted for array elements, resulting in lower system utilization.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide the audio processing method and the device suitable for the hidden communication of the active noise reduction system, which can shorten the response time of the communication system, simplify the structure of the communication system and realize the purpose of the remote and multi-angle concurrent hidden communication on the premise of low cost.
The aim of the invention can be achieved by the following technical scheme: an audio processing method suitable for hidden communication of an active noise reduction system comprises the following steps:
s1, acquiring original audio, and intercepting a pre-sent frequency band signal from the original audio;
s2, modulating the intercepted frequency band signals to mutually non-overlapping ultrasonic wave bands;
s3, combining the modulated audio into a combined audio;
s4, calculating the phase delay of the audio sent by each array element in the phased array according to the position direction of the active noise reduction system and the frequency band distribution of the combined audio;
s5, compensating in the phase spectrum of the combined audio according to the calculated phase delay, and then sending out the compensated combined audio through a phased array;
s6, the active noise reduction system receives the combined audio, generates original audio through a receiving circuit, combines with an active noise reduction algorithm for processing, and restores to obtain an acoustic signal.
Further, the original audio in step S1 is specifically obtained by a software system or by a recording method.
Further, the specific process of intercepting the pre-sent frequency band signal from the original audio in the step S1 is as follows:
converting the original audio frequency from a time domain to a frequency domain by utilizing Fourier transform, and then intercepting a frequency domain signal with the selected bandwidth within a preset range of 3kHz in the frequency domain signal, namely the pre-sent frequency band signal.
Further, the specific process of step S2 is as follows:
and copying the selected frequency band signal to a target frequency band on the frequency spectrum obtained by Fourier transformation, and then setting the selected frequency band to zero.
Further, the specific process of step S3 is as follows:
and combining all the audio signals in different frequency bands on the frequency spectrum to obtain a new complete spectrogram, and then obtaining the audio signals in the time domain through inverse Fourier transformation, namely the combined audio.
Further, the step S4 specifically considers the band distribution compensation and the target angle offset compensation to calculate the phase delay of the audio transmitted by each array element in the phased array.
Further, the step S5 specifically includes the following steps:
s51, compensating the phase delay in the phase spectrum of the combined audio, and obtaining audio signals which need to be played by array elements in the time domain through inverse Fourier transform;
s52, converting the audio signal obtained in the step S51 from a digital signal to an analog signal, and then amplifying the signal power of the analog signal;
and S53, the amplified analog signals are connected into a phased array formed by a plurality of ultrasonic sensors, and the phased array converts the electric signals into ultrasonic signals to realize transmission.
Further, the phased array in step S53 is formed by arranging a plurality of ultrasonic sensors in a straight line.
Further, the step S6 specifically includes the following steps:
s61, the active noise reduction system receives the combined audio, and the receiving circuit generates electric signals corresponding to all the audio before modulation;
s62, the electric signals generated by the receiving circuit are processed through an active noise reduction algorithm, and acoustic signals are restored.
The audio processing device comprises an audio transmitting end and a receiving end, wherein the transmitting end comprises a computer, an external sound card, a power amplifier and a phased array formed by a plurality of ultrasonic sensors, and the computer is connected with the external sound card through a USB interface and is used for converting a plurality of paths of digital audio signals generated in advance into analog signals;
the output end of the external sound card is connected with a plurality of power amplifiers with the same number and is used for improving the transmission power of signals;
the output of each power amplifier is connected with an ultrasonic sensor to send ultrasonic signals;
the receiving end is specifically an active noise reduction system, the active noise reduction system generates electric signals of all audios before modulation through nonlinear effects of a receiving circuit, and the electric signals are processed by an active noise reduction algorithm and can be restored into sound signals to be played in an internal loudspeaker.
Compared with the prior art, the invention has the following advantages:
according to the invention, firstly, partial frequency bands in the pre-sent original audio are intercepted, then the audio in the frequency bands are respectively modulated to different ultrasonic wave bands, and then according to the direction position of the active noise reduction system, the phased array technology is combined, and the audio in the different frequency bands is added with corresponding phase delays and is distributed to array elements for playing. Because the played audio belongs to ultrasonic waves and cannot be directly heard by people, after the audio is received by the active noise reduction system, the receiving circuit of the active noise reduction system generates electric signals of all the audios before modulation through nonlinear effect, and the electric signals are processed by the active noise reduction algorithm and can be restored into acoustic signals. Therefore, the audible and meaningful sound signal can be directly received only by sending the modulated signal at the sending end without any operation on an active noise reduction system of the receiving end, the system response time is short, the structure is simple, and the aim of remote and multi-angle concurrent hidden communication can be fulfilled on the premise of low cost.
The invention uses Fourier transformation to transform the original audio frequency from time domain to frequency domain, intercepts the selected frequency domain signal in the frequency domain signal, copies the selected frequency band signal to the target frequency band on the frequency spectrum obtained by Fourier transformation, then sets the selected frequency band to zero, modulates the intercepted frequency band signal to the ultrasonic wave band which is not overlapped with each other, combines the audio signals in different frequency bands on the frequency spectrum to obtain a new complete spectrogram, then obtains the audio signal on the time domain by inverse Fourier transformation, namely the combined audio frequency, and further considers the frequency band distribution compensation and the target angle offset compensation to calculate the phase delay of the audio frequency sent by each array element in the phased array for compensation in the phase spectrum of the combined audio frequency. Therefore, on the premise of ensuring the consistent signal strength, the utilization rate of a communication channel is improved through a frequency division multiplexing technology, and the wide-frequency and multidirectional sound wave focusing and enhancing functions are realized by combining the frequency division multiplexing technology and a phased array technology.
Drawings
FIG. 1 is a schematic flow chart of the method of the present invention;
FIG. 2 is a flow chart of signal processing at an audio transmitting end in the present invention;
FIG. 3 is a signal processing flow chart of an audio receiving end in the invention;
FIG. 4 is a schematic diagram of a hardware device according to the present invention;
the figure indicates: 1. the system comprises a computer, 2 external sound cards, 3 power amplifiers, 4 phased arrays, 5 active noise reduction systems.
Detailed Description
The invention will now be described in detail with reference to the drawings and specific examples.
Examples
As shown in fig. 1, an audio processing method suitable for hidden communication of an active noise reduction system includes the following steps:
s1, acquiring original audio, and intercepting a pre-sent frequency band signal from the original audio;
s2, modulating the intercepted frequency band signals to mutually non-overlapping ultrasonic wave bands;
s3, combining the modulated audio into a combined audio;
s4, calculating the phase delay of the audio sent by each array element in the phased array according to the position direction of the active noise reduction system and the frequency band distribution of the combined audio;
s5, compensating in the phase spectrum of the combined audio according to the calculated phase delay, and then sending out the compensated combined audio through a phased array;
s6, the active noise reduction system receives the combined audio, generates original audio through a receiving circuit, combines with an active noise reduction algorithm for processing, and restores to obtain an acoustic signal.
The technical scheme is applied to the embodiment, and specifically:
(1) Obtaining original audio by using a software system generating or recording method, wherein the number of the original audio can be arbitrarily selected;
(2) Converting the obtained original audio frequency from a time domain to a frequency domain by utilizing Fourier transformation, and intercepting a selected part of the frequency domain signals, wherein the selected part of the frequency domain signals is the frequency domain signal with the most concentrated energy and bandwidth of about 3kHz according to the observed audio frequency spectrum;
(3) Modulating the intercepted audio signals to mutually non-overlapping ultrasonic wave bands in the following modulation modes: copying the selected frequency band to a target frequency band on the frequency spectrum obtained by Fourier transformation, and setting the selected frequency band to zero;
(4) Combining the ultrasonic audio which are not overlapped with each other in frequency bands into an audio A, and completely reserving frequency bands of a plurality of audio before combination in the frequency spectrum of the combined audio A, wherein the audio combining method comprises the following steps: combining all audio signals in different frequency bands on a frequency spectrum to obtain a new complete spectrogram, and then obtaining an audio signal in a time domain through inverse Fourier transform;
(5) According to the position direction of the active noise reduction system and the frequency band distribution of the combined audio A, calculating the phase delay of the audio sent by each array element in the phased array, and considering frequency band distribution compensation and target angle offset compensation during phase delay compensation calculation;
(6) Compensating the phase delay calculated in the step (5) in the phase spectrum of the combined audio A, and obtaining audio signals which need to be played by array elements in the time domain through inverse Fourier transform;
(7) Converting the audio frequency obtained in the step (6) from a digital signal to an analog signal by utilizing a multi-channel sound card, and then connecting the analog signal to a power amplifier to improve the signal power, wherein in the embodiment, the sampling rate of the sound card is more than 48kHz, and the amplification factor of the power amplifier is more than 15 times;
(8) The signal in the step (7) is connected into a phased array formed by a plurality of ultrasonic sensors, the ultrasonic sensors convert electric signals into ultrasonic signals to realize transmission, in the embodiment, the ultrasonic sensors with high pressure resistance, high power and center frequency above 20kHz are selected, and the phased array formed by the ultrasonic sensors is arranged in a straight line;
(9) The active noise reduction system receives the audio frequency sent by the (8), the receiving circuit generates electric signals of all the audio frequencies before modulation, the electric signals are processed by the active noise reduction algorithm and can be restored into sound signals to be broadcast by the internal loudspeaker, wherein the active noise reduction system refers to: systems for playing signals received by an external microphone using an internal speaker to counteract the effects of external noise, such as: earphone noise reduction, automobile noise reduction and the like, and the receiving circuit thereof generates electric signals of various audios before modulation through nonlinear effect.
Fig. 2 shows a signal processing flow of the audio transmitting end in the present embodiment, and the following processing steps of the audio transmitting end are described in detail below with reference to fig. 2 by taking three original audio as an example:
in step 301, three original audios A, B, C are obtained by means of generating or recording by a software system, and then step 302 is executed;
in step 302, the audio A, B, C is converted from the time domain to the frequency domain by fourier transformation, the energy distribution is observed, the characteristic parts (for example, 0 to 2 kHz) are intercepted to obtain the audio a, b and c, and then step 303 is performed;
in step 303, the audio frequencies a, b, c are modulated to 18-20kHz, 20-22kHz, 22-24kHz, respectively, and then step 304 is performed;
in step 304, the three modulated audios are combined into an audio D, 18-20kHz of the spectrum thereof is the modulated audio a,20-22kHz is the modulated audio b,22-24kHz is the modulated audio c, and then step 305 is performed;
in step 305, the phased array neutral position is set to 0 degrees, the right side is negative, and the left side is positive. Assuming that a audio needs to be played in the 30-degree direction, b audio needs to be played in the 0-degree direction, c audio needs to be played in the-30-degree direction, calculating the phase delay corresponding to each array element by taking a 4-array element phased array as an example according to the respective frequency distribution conditions of the audio a, the audio b and the audio c and the orientation angles of the audio a, b and c, and then executing step 306;
in step 306, the phase delay calculated in step 305 is compensated to the phase spectrum of the audio D, and the audio is transformed from the frequency domain to the time domain by using the inverse fourier transform, and then step 307 is performed;
in step 307, the phased array transmits audio D.
Fig. 3 shows a signal processing flow of the audio receiving end in the present embodiment, taking a noise reduction earphone in an active noise reduction system as an example, and assuming that the noise reduction earphone is located in the 0 degree direction of the phased array, the following steps are described in detail with reference to fig. 3:
in step 308, the active noise reduction earphone external microphone at the 0 degree position receives the audio D sent by the phased array, and then step 309 is performed;
in step 309, the receiving circuit generates an electrical signal of audio b due to nonlinear effects, and then performs step 310;
in step 310, the active noise reduction algorithm misuses that the noise b exists in the outside, so that the inverted sound wave of the audio b is played in the internal speaker, and then step 311 is performed;
in step 311, the person wearing the active noise reduction headphones may hear audio b.
The embodiment also provides a device suitable for long-distance and multi-angle hidden communication of the active noise reduction system, and as shown in fig. 4, the device comprises an audio sending end and a receiving end. The transmitting end comprises a computer 1, an external sound card 2, a power amplifier 3 and a phased array 4 formed by ultrasonic sensors. The computer 1 is connected with the external sound card 2 through a USB interface, and can convert the pre-generated multipath digital audio signals into analog signals; the output end of the sound card 2 is connected with a plurality of power amplifiers 3 with the same number, and the part is used for improving the transmission power of signals; the output of each power amplifier 3 is connected with an ultrasonic sensor to send ultrasonic signals, and a plurality of ultrasonic sensors form a phased array 4 in a linear arrangement mode.
The receiving end is the active noise reduction system 5. The system generates electric signals of all audios before modulation through nonlinear effect of a receiving circuit, and the electric signals are processed by an active noise reduction algorithm and can be restored into sound signals to be played in an internal loudspeaker.
Claims (10)
1. An audio processing method suitable for hidden communication of an active noise reduction system is characterized by comprising the following steps:
s1, acquiring original audio, and intercepting a pre-sent frequency band signal from the original audio;
s2, modulating the intercepted frequency band signals to mutually non-overlapping ultrasonic wave bands;
s3, combining the modulated audio into a combined audio;
s4, calculating the phase delay of the audio sent by each array element in the phased array according to the position direction of the active noise reduction system and the frequency band distribution of the combined audio;
s5, compensating in the phase spectrum of the combined audio according to the calculated phase delay, and then sending out the compensated combined audio through a phased array;
s6, the active noise reduction system receives the combined audio, generates original audio through a receiving circuit, combines with an active noise reduction algorithm for processing, and restores to obtain an acoustic signal.
2. The audio processing method according to claim 1, wherein the original audio in step S1 is obtained by a software system or by a recording method.
3. The audio processing method for covert communication of an active noise reduction system according to claim 1, wherein the specific process of intercepting the pre-transmitted frequency band signal from the original audio in step S1 is as follows:
converting the original audio frequency from a time domain to a frequency domain by utilizing Fourier transform, and then intercepting a frequency domain signal with the selected bandwidth within a preset range of 3kHz in the frequency domain signal, namely the pre-sent frequency band signal.
4. The audio processing method for covert communication of active noise reduction system according to claim 3, wherein the specific process of step S2 is as follows:
and copying the selected frequency band signal to a target frequency band on the frequency spectrum obtained by Fourier transformation, and then setting the selected frequency band to zero.
5. The audio processing method for the active noise reduction system according to claim 4, wherein the specific process of step S3 is as follows:
and combining all the audio signals in different frequency bands on the frequency spectrum to obtain a new complete spectrogram, and then obtaining the audio signals in the time domain through inverse Fourier transformation, namely the combined audio.
6. The audio processing method according to claim 1, wherein the step S4 is specifically implemented by considering frequency band distribution compensation and target angle offset compensation to calculate a phase delay of the audio transmitted by each array element in the phased array.
7. The audio processing method for the active noise reduction system according to claim 5, wherein the step S5 specifically comprises the following steps:
s51, compensating the phase delay in the phase spectrum of the combined audio, and obtaining audio signals which need to be played by array elements in the time domain through inverse Fourier transform;
s52, converting the audio signal obtained in the step S51 from a digital signal to an analog signal, and then amplifying the signal power of the analog signal;
and S53, the amplified analog signals are connected into a phased array formed by a plurality of ultrasonic sensors, and the phased array converts the electric signals into ultrasonic signals to realize transmission.
8. The audio processing method for hidden communication of active noise reduction system according to claim 7, wherein the phased array in step S53 is composed of a plurality of ultrasonic sensors arranged in a line shape.
9. The audio processing method for the active noise reduction system according to claim 7, wherein the step S6 specifically comprises the following steps:
s61, the active noise reduction system receives the combined audio, and the receiving circuit generates electric signals corresponding to all the audio before modulation;
s62, the electric signals generated by the receiving circuit are processed through an active noise reduction algorithm, and acoustic signals are restored.
10. An audio processing device based on the audio processing method suitable for the hidden communication of the active noise reduction system according to claim 1, which is characterized by comprising an audio transmitting end and a receiving end, wherein the transmitting end comprises a computer (1), an external sound card (2), a power amplifier (3) and a phased array (4) consisting of a plurality of ultrasonic sensors, and the computer (1) is connected with the external sound card (2) through a USB interface and is used for converting a plurality of pre-generated digital audio signals into analog signals;
the output end of the external sound card (2) is connected with a plurality of power amplifiers (3) with the same number and is used for improving the transmission power of signals;
the output of each power amplifier (3) is connected with an ultrasonic sensor to send ultrasonic signals;
the receiving end is specifically an active noise reduction system (5), the active noise reduction system (5) generates electric signals of all audios before modulation through nonlinear effects of a receiving circuit, and the electric signals are processed by an active noise reduction algorithm and can be restored into sound signals to be played in an internal loudspeaker.
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