Howling suppression method and device, sound amplification equipment and storage medium

Abstract

The invention relates to the technical field of audio, and provides a howling suppression method and device, a sound amplification device and a storage medium, a microphone receives a mixed signal of sound played by the sound amplification device, and the mixed signal comprises a pulse modulation signal obtained by modulating a pulse signal generated by the microphone and then performing frequency shift to a target frequency band; and a normal pickup signal of the microphone; demodulating the mixed signal according to the pulse modulation signal to obtain a pulse demodulation signal; calculating the distance between the microphone and the loudspeaker according to the pulse demodulation signal; and dynamically adjusting the current gain of the microphone according to the distance so as to suppress howling. According to the application, the distance between the microphone and the loudspeaker can be accurately calculated by using the pulse modulation and demodulation technology, and the gain of the microphone is dynamically adjusted according to the distance, so that the squeal phenomenon is effectively inhibited.

Description

Technical Field

[0001] This application relates to the field of audio technology, and particularly to a method and device for suppressing howling, a sound amplification device, and a storage medium. Background Art

[0002] Howling, also known as self-excited oscillation or feedback howling, usually occurs when the sound signal picked up by the microphone is amplified and played back through the speaker, and then these sound signals are picked up by the microphone again and amplified again, forming a closed feedback loop. When the gain of this loop exceeds a certain threshold, the system will generate a strong screeching sound, that is, the howling phenomenon. The howling phenomenon not only affects the sound quality and effect of the sound amplification system, but may also cause discomfort to the listening experience of the audience.

[0003] In the prior art, there are algorithms for suppressing the howling phenomenon of microphone amplification, but these algorithms cannot completely suppress howling. Summary of the Invention

[0004] Based on this, this application proposes a method and device for suppressing howling, a sound amplification device, and a storage medium, aiming to achieve the effect of completely suppressing howling in microphone amplification.

[0005] The first aspect of this application provides a method for suppressing howling, and the method includes:

[0006] Receiving a mixed signal of the sound played by the loudspeaker through the microphone, where the mixed signal includes: a pulse modulation signal obtained by modulating the pulse signal generated by the microphone and shifting the frequency to a target frequency band, and the normal sound pickup signal of the microphone;

[0007] Demodulating the mixed signal according to the pulse modulation signal to obtain a pulse demodulation signal;

[0008] Calculating the distance between the microphone and the loudspeaker according to the pulse demodulation signal;

[0009] Dynamically adjusting the current gain of the microphone according to the distance to suppress howling.

[0010] Optionally, the demodulating the mixed signal according to the pulse modulation signal to obtain a pulse demodulation signal includes:

[0011] Filtering the mixed signal and extracting a frequency band signal centered on the carrier frequency of the pulse modulation signal;

[0012] Demodulating the extracted frequency band signal to obtain a pulse demodulation signal.

[0013] Optionally, the calculating the distance between the microphone and the loudspeaker according to the pulse demodulation signal includes:

[0014] Determine the first moment when the microphone outputs a pulse signal to the loudspeaker;

[0015] Determine the fixed delay inside the loudspeaker;

[0016] Identify the second moment of the pulse peak in the pulse demodulation signal;

[0017] Calculate the distance between the microphone and the loudspeaker according to the delay, the first moment, the second moment and the sound propagation speed.

[0018] Optionally, the dynamically adjusting the current gain of the microphone according to the distance to suppress howling includes:

[0019] Compare the distance with a preset howling suppression distance threshold and a preset gain suppression distance threshold;

[0020] When the distance is less than the preset howling suppression distance threshold, adjust the current gain of the microphone according to the distance, and the gain is proportional to the distance;

[0021] When the distance is less than or equal to the preset gain suppression distance threshold, adjust the current gain of the microphone to a preset first value to achieve complete howling suppression;

[0022] Wherein, the preset howling suppression distance threshold is greater than the preset gain suppression distance threshold.

[0023] Optionally, the method further includes.

[0024] When the distance is greater than the preset howling suppression distance threshold, adjust the current gain of the microphone to a preset second value to restore the normal sound amplification function.

[0025] Optionally, the method further includes:

[0026] Filter the normal sound pickup signal of the microphone to obtain a filtered signal;

[0027] Merge the pulse modulation signal and the filtered signal to obtain a merged signal;

[0028] Output the merged signal to the loudspeaker for playback.

[0029] Optionally, the cut-off frequency for filtering the normal sound pickup signal of the microphone is lower than the carrier frequency of the pulse modulation signal.

[0030] The second aspect of the present application provides a howling suppression device, and the device includes:

[0031] A receiving module, configured to receive a mixed signal of the sound played by a loudspeaker through a microphone, where the mixed signal includes: a pulse modulation signal obtained by modulating a pulse signal generated by the microphone and shifting the frequency to a target frequency band, and a normal sound pickup signal of the microphone;

[0032] A demodulation module, configured to demodulate the mixed signal according to the pulse modulation signal to obtain a pulse demodulation signal;

[0033] A calculation module, configured to calculate a distance between the microphone and the loudspeaker according to the pulse demodulation signal;

[0034] A suppression module, configured to dynamically adjust a current gain of the microphone according to the distance to suppress howling.

[0035] A third aspect of the present application provides a sound amplification device, where the sound amplification device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the howling suppression method are implemented.

[0036] A fourth aspect of the present application provides a computer-readable storage medium, where the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the howling suppression method are implemented.

[0037] The present application receives a mixed signal of the sound played by a loudspeaker through a microphone, where the mixed signal includes: a pulse modulation signal obtained by modulating a pulse signal generated by the microphone and shifting the frequency to a target frequency band, and a normal sound pickup signal of the microphone. The pulse signal generated by the microphone is modulated and its frequency is shifted to a target frequency band, so that the modulated pulse signal has specific frequency characteristics, and thus the mixed signal can be demodulated according to the pulse modulation signal to obtain a pulse demodulation signal. Then, the distance between the microphone and the loudspeaker is calculated according to the pulse demodulation signal. Finally, the current gain of the microphone is dynamically adjusted according to the distance to suppress howling. The present application uses pulse modulation and demodulation technologies, can accurately calculate the distance between the microphone and the loudspeaker, and dynamically adjust the gain of the microphone according to the distance, thereby effectively suppressing the howling phenomenon. Description of the Drawings

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0039] Figure 1 It is a schematic flowchart of the howling suppression method provided by an embodiment of the present application.

[0040] Figure 2 It is a schematic data flow diagram of the howling suppression method provided by an embodiment of the present application.

[0041] Figure 3 It is a functional module diagram of the howling suppression device provided by an embodiment of the present application.

[0042] Figure 4 It is a schematic structural diagram of a sound amplification device provided by an embodiment of the present application. Detailed implementation manners

[0043] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present application.

[0044] In modern audio technology, microphone sound amplification systems are widely used in various occasions, such as speeches, conferences, performances, entertainment activities, etc. As a key device for sound collection, a microphone converts a sound signal into an electrical signal, which is then amplified and processed and played out through a speaker device such as a speaker. However, during the use of microphone sound amplification, a common and uncomfortable problem is the howling phenomenon.

[0045] Howling, also known as self-excited oscillation or feedback howling, usually occurs after the sound signal picked up by the microphone is amplified and played out through the speaker, and these sound signals are picked up by the microphone again and amplified again, forming a closed feedback loop. When the gain of this loop exceeds a certain threshold, the system will generate a strong screeching sound, that is, the howling phenomenon. The howling phenomenon not only affects the sound quality and effect of the sound amplification system, but also may cause discomfort to the listening experience of the audience.

[0046] In the prior art, there are methods such as the co-sense frequency shift algorithm, the equalizer adjustment algorithm, the noise gate algorithm, and the echo cancellation algorithm to suppress the howling of microphone sound amplification. However, the effect of the frequency shift algorithm in suppressing howling is limited, and it will cause sound distortion. Adjusting the equalizer (EQ) makes the sound prone to distortion, and it needs to be calibrated in advance according to the use environment and equipment, and it cannot suppress 100%. The noise gate algorithm can completely suppress howling in some cases, but the sound has a sense of jerk at the switch, and if the volume picked up by the microphone exceeds a certain threshold, there is no suppression effect at all, and sudden howling is likely to occur. The echo cancellation algorithm can achieve deep suppression, but the algorithm is complex and the computational amount is large, resulting in the necessity to use high-cost high-end chips. At the same time, it cannot guarantee 100% suppression, and the sound may also be distorted.

[0047] To completely suppress howling, the present application provides a howling suppression method, device, sound amplification device, and storage medium.

[0048] Figure 1 It is a schematic flowchart of the howling suppression method provided by the embodiments of the present application. The howling suppression method includes the following steps.

[0049] S11, receiving a mixed signal of the sound played by the loudspeaker through the microphone.

[0050] The howling suppression method can be applied to a sound amplification device, which includes a microphone and a loudspeaker. A microphone, also known as a microphone, is a transducer that converts sound into an electrical signal. A loudspeaker, also known as a speaker, is a conversion device that converts electrical energy into sound energy. The microphone is responsible for sound collection, then processes and amplifies it through an internal circuit, and finally plays it out through a speaker or loudspeaker.

[0051] In an optional embodiment, the mixed signal of the sound played by the loudspeaker received by the microphone includes: a pulse modulation signal obtained by modulating the pulse signal generated by the microphone and shifting its frequency to a target frequency band, and the normal sound pickup signal of the microphone.

[0052] The microphone itself generates a continuous pulse signal p0. The pulse signal p0 is a periodic pulse signal, and its pulse width and interval are adjustable. The pulse signal p0 generated by the microphone is modulated and shifted to a target frequency band to obtain a pulse modulation signal, which is combined with the normal sound pickup signal s0 of the microphone to obtain a combined signal, and finally the combined signal is output to the loudspeaker for playback.

[0053] Among them, modulating the pulse signal generated by the microphone and shifting its frequency to a target frequency band means modulating the pulse signal generated by the microphone and shifting its frequency to a frequency band inaudible to the human ear. The frequency band inaudible to the human ear can be a frequency band above 30 kHz, i.e., an ultrasonic frequency band. The modulated pulse modulation signal is shifted to the target frequency band to obtain a modulation signal with a carrier frequency of f0.

[0054] Since the sound output from the microphone to the loudspeaker is an analog signal, the original pulse signal generated by the microphone uses an analog modulation method to convert these pulse signals into modulated analog signals. The modulation method for the pulse signal can be amplitude modulation, frequency modulation, or phase modulation.

[0055] In addition, in practical applications, the microphone may pick up various sound signals, including ambient noise, other sound sources, etc. Through modulation and frequency shifting, the pulse signal can be converted to a relatively independent frequency band, thus avoiding overlap with the original audio signal (i.e., the normal sound pickup signal of the microphone) and other potential interference signals.

[0056] In an optional embodiment, the method further comprises:

[0057] Filtering the normal sound pickup signal of the microphone to obtain a filtered signal;

[0058] Combining the pulse modulation signal with the filtered signal to obtain a combined signal;

[0059] The combined signal is output to the loudspeaker for playback.

[0060] The normal sound pickup signal s0 of the microphone is low-pass filtered to obtain the filtered sound signal s1 (i.e., the filtered signal). Low-pass filtering is a filtering method that only allows low-frequency signals to pass through and attenuates high-frequency signals. Low-pass filtering the normal sound pickup signal of the microphone can reduce noise interference and improve the quality of the audio signal. In particular, filtering can significantly reduce the impact of noise within a specific frequency range.

[0061] The cutoff frequency for filtering the sound pickup signal is lower than the carrier frequency of the pulse modulation signal. The cutoff frequency is the highest frequency allowed to pass through the filter. The carrier frequency and signals near it are considered high-frequency components. The cutoff frequency of the filter is set to be lower than the carrier frequency of the pulse modulation signal in order to ensure that the carrier frequency and signals near it are effectively attenuated or removed, thereby improving the purity and clarity of the audio signal.

[0062] The pulse modulation signal (the signal after modulation and frequency shifting) is combined with the filtered signal to obtain a combined signal. The combined signal can retain most of the information of the original picked-up signal, while adding or emphasizing certain specific signal components (such as the pulse modulation signal), which helps to achieve specific sound effects or functions during playback.

[0063] Finally, the combined signal is output to the loudspeaker, amplified and converted into sound output.

[0064] S12, demodulating the mixed signal according to the pulse modulation signal to obtain a pulse demodulation signal.

[0065] Demodulation is the reverse process of modulation, which aims to recover the original information from the modulated signal.

[0066] The characteristics of the known pulse modulation signal (such as pulse shape, width, modulation mode, etc.) can be used as a reference to analyze and process the mixed signal. By identifying the part of the mixed signal that matches the characteristics of the pulse modulation signal, the pulse modulation signal can be separated and the original information can be further extracted. After demodulation, the pulse modulation signal separated from the mixed signal is the pulse demodulation signal.

[0067] The pulse demodulation signal is similar in form to the original pulse modulation signal, but other interference components in the mixed signal have been removed.

[0068] In an alternative embodiment, demodulating the mixed signal according to the pulse modulation signal to obtain a pulse demodulation signal includes:

[0069] Filtering the mixed signal and extracting a frequency band signal centered on the carrier frequency of the pulse modulation signal;

[0070] Demodulating the extracted frequency band signal to obtain a pulse demodulation signal.

[0071] The mixed signal is band-pass filtered using a band-pass filter, with the aim of extracting a frequency band signal centered on the carrier frequency of the pulse modulation signal from the mixed signal.

[0072] The band-pass filter allows signals within a certain specific frequency range to pass through while attenuating signals of other frequencies. In the embodiments of the present application, the center frequency of the filter is set to the carrier frequency of the pulse modulation signal, thereby allowing signal components close to this frequency to pass through.

[0073] After band-pass filtering, most of the interference and noise in the mixed signal are removed, leaving the signal components related to the carrier frequency of the pulse modulation signal.

[0074] S13. Calculate the distance between the microphone and the loudspeaker according to the pulse demodulation signal.

[0075] In a sound propagation scenario, the microphone receives a sound signal and converts it into an electrical signal, which is then modulated (e.g., by pulse modulation) for easy transmission. The loudspeaker then receives this modulated signal, demodulates it, and restores it to the original sound signal for playback.

[0076] By comparing the transmitted pulse signal and the received and demodulated pulse signal, the time delay between them can be measured. This time delay is actually the time required for sound to propagate from the microphone to the loudspeaker. Finally, using the relationship between the sound propagation speed and the time delay, i.e., distance = speed × time, the distance between the microphone and the loudspeaker can be calculated.

[0077] In order to obtain an accurate distance measurement, in an alternative embodiment, calculating the distance between the microphone and the loudspeaker according to the pulse demodulation signal includes:

[0078] Determine the first moment when the microphone outputs a pulse signal to the loudspeaker;

[0079] Determine the fixed delay inside the loudspeaker;

[0080] Identify the second moment of the pulse peak in the pulse demodulation signal;

[0081] Calculate the distance between the microphone and the loudspeaker according to the delay, the first moment, the second moment and the sound propagation speed.

[0082] At a preset time point t0, the microphone sends an adjusted pulse signal p0 to the loudspeaker. The pulse signal p0 has sufficient amplitude and frequency characteristics to facilitate subsequent signal identification and demodulation. Record the time point t0 as the first moment.

[0083] After receiving the pulse signal p0, the loudspeaker starts to play the signal after an internal fixed delay Ta. This internal delay may be determined by various factors such as the circuit processing of the loudspeaker and the speaker response, and is usually known or can be obtained through calibration in practical applications.

[0084] The microphone then receives the mixed signal containing the sound played by the loudspeaker. In order to extract the information of the pulse signal p0 from the mixed signal, the frequency band centered on the carrier frequency of the pulse signal p0 in the mixed signal can be demodulated. In the demodulated pulse signal (i.e., the pulse demodulation signal), the moment t1 (denoted as the second moment) of the pulse peak is accurately identified by detecting the zero-crossing point or peak point of the signal. The moment t1 represents the exact time when the microphone receives the pulse signal played by the loudspeaker.

[0085] The distance D between the microphone and the loudspeaker is calculated by the following formula: D = (t1 - t0 - Ta) * s, where s is the sound propagation speed in the air.

[0086] In the above optional implementation, by accurately measuring the pulse transmission moment t0 and the pulse peak reception moment t1, and combining the internal delay Ta of the loudspeaker and the sound propagation speed s, high-precision distance calculation can be achieved. Identifying the pulse peak moment through the demodulated pulse signal can effectively reduce the influence of noise and interference on the measurement result and improve the reliability of the measurement. Provide accurate distance information for howling suppression, thereby helping to optimize the performance of the sound reinforcement system and reduce the occurrence of howling phenomena.

[0087] In an alternative embodiment, the current environmental conditions may also be obtained, and the sound propagation speed may be corrected based on the current environmental conditions using a preset correction formula or model to obtain the corrected sound propagation speed. The distance D between the microphone and the loudspeaker is calculated using the transmission pulse time t0, the received pulse peak time t1, the internal delay Ta of the loudspeaker, and the corrected sound propagation speed s. The preset correction formula or model is: speed of sound = (γ·R·T) / M, where γ is the specific heat ratio, R is the gas constant, T is the absolute temperature, and M is the molecular weight. In this way, the present application can be applied to distance measurement under different environments and conditions, and only the sound propagation speed s needs to be appropriately corrected.

[0088] S14. Dynamically adjust the current gain of the microphone according to the distance to suppress howling.

[0089] Howling is usually caused by the microphone picking up the sound amplified by the loudspeaker and amplifying it again, forming a positive feedback loop. By adjusting the gain of the microphone, the intensity of the input signal can be controlled, thus avoiding the occurrence of howling.

[0090] In an alternative embodiment, before dynamically adjusting the current gain of the microphone according to the distance, the method may further include:

[0091] Judge whether to perform howling suppression operation according to the distance.

[0092] The distance between the microphone and the loudspeaker is one of the important factors affecting the risk of howling. The closer the distance, the higher the risk of howling; the farther the distance, the lower the risk of howling. Therefore, before dynamically adjusting the current gain of the microphone, first judge whether there is a howling risk in the current situation according to the measured distance, that is, judge whether it is necessary to perform howling suppression operation.

[0093] Through the pre-judgment step, the howling suppression operation can be avoided in unnecessary situations, that is, the operation in unnecessary situations can be avoided so as not to affect the amplification intensity and sound quality, thereby improving the overall efficiency and amplification quality of the system. Dynamically adjusting the microphone gain may consume certain system resources. By judging whether it is necessary to perform howling suppression, these resources can be saved and the service life of the system can be extended.

[0094] In an alternative embodiment, the judging whether to perform howling suppression operation according to the distance includes:

[0095] Compare the distance with a preset howling distance threshold;

[0096] If the distance is less than or equal to the preset howling distance threshold, it is determined to perform howling suppression operation;

[0097] If the distance is greater than a preset howling distance threshold, it is determined not to perform howling suppression operation.

[0098] The preset howling distance threshold can be set according to the characteristics of the microphone and the loudspeaker, environmental conditions, and the requirements of the application scenario, and is used to determine whether the current distance may cause howling.

[0099] Compare the calculated distance with the preset howling distance threshold. If the distance is less than or equal to the preset howling distance threshold, it indicates that there is a high howling risk at the current distance. Therefore, it is determined that howling suppression operation needs to be performed, such as by dynamically adjusting the microphone gain to reduce the intensity of the input signal, so as to avoid the occurrence of howling. If the distance is greater than the preset howling distance threshold, it indicates that the howling risk is low at the current distance. Therefore, it is determined that no howling suppression operation is required to save resources and avoid unnecessary adjustments.

[0100] The above optional implementation manner realizes howling suppression based on the relationship between the distance and the howling risk and the principle of dynamically adjusting the gain. When the distance is close and the howling risk is high, the input signal intensity can be reduced by reducing the gain, so as to avoid the occurrence of howling. When the distance is far and the howling risk is low, such adjustments are not required.

[0101] In an optional implementation manner, the dynamically adjusting the current gain of the microphone according to the distance to suppress howling includes:

[0102] Compare the distance with a preset howling suppression distance threshold and a preset gain suppression distance threshold;

[0103] When the distance is less than the preset howling suppression distance threshold, adjust the current gain of the microphone according to the distance, and the gain is proportional to the distance;

[0104] When the distance is less than or equal to the preset gain suppression distance threshold, adjust the current gain of the microphone to a preset first value to achieve complete howling suppression.

[0105] Wherein, the preset howling suppression distance threshold is greater than the preset gain suppression distance threshold.

[0106] The preset howling suppression distance threshold and the preset gain suppression distance threshold are respectively used to determine whether to start howling suppression and whether to completely suppress howling.

[0107] When the distance is less than the preset howling suppression distance threshold, it indicates that there is a risk of howling at the current distance. To reduce the howling risk, it is necessary to adjust the current gain of the microphone. By adjusting the gain of the microphone output signal, the intensity of the input signal can be adjusted. Since howling usually occurs when the distance between the microphone and the loudspeaker (or speaker) is too close, at this time the microphone is likely to pick up the sound amplified by the speaker and amplify it again, forming a positive feedback loop. To suppress howling, it is necessary to reduce the gain of the microphone to reduce the intensity of the input signal. When the distance continues to decrease, the risk of howling continues to increase, so the gain can be correspondingly further reduced to continue to reduce the intensity of the input signal. In the embodiment of the present application, the gain k can be determined according to the calculated distance D, where the value of the gain k is proportional to the distance D. That is, the smaller the distance, the lower the gain. Applying the gain k to the filtered sound signal s1, the adjusted sound signal s2 is obtained, that is, s2 = k * s1, and the adjusted sound signal s2 is output to the loudspeaker for playback. By adjusting the gain to be proportional to the distance, the risk of howling can be effectively reduced while maintaining the sound quality.

[0108] When the distance is less than or equal to the preset gain suppression distance threshold, it indicates that the risk of howling at the current distance is very high. To completely avoid the occurrence of howling, it is necessary to adjust the current gain of the microphone to a preset first value (the preset first value can be 0). That is, the microphone is completely turned off, thereby achieving complete howling suppression. Completely turning off the microphone completely stops the sound amplification function.

[0109] The reason for setting the howling suppression distance threshold to be greater than the gain suppression distance threshold is to provide a buffer zone. When the distance decreases to the howling suppression distance threshold, the gain is adjusted to reduce the howling risk instead of immediately turning off the microphone. This can ensure that there is enough time to smoothly adjust the gain during the gradual increase of the howling risk, avoiding the impact of sudden gain changes on the sound quality. Only when the distance decreases to the gain suppression distance threshold or below, more extreme measures will be taken, that is, completely turning off the microphone, to ensure that howling is completely suppressed.

[0110] In the above optional embodiment, by refining the gain adjustment strategy and setting two preset distance thresholds (the howling suppression distance threshold and the gain suppression distance threshold), different gain adjustment strategies can be adopted at different distances, achieving smooth gain adjustment and reliable howling suppression. It can not only reduce the howling risk but also maintain good sound quality. In extreme cases, the howling can be completely suppressed by completely turning off the microphone, improving the flexibility and reliability of the system.

[0111] In an optional embodiment, the method further includes.

[0112] When the distance is greater than the preset howling suppression distance threshold, adjust the current gain of the microphone to a preset second value to restore the normal sound amplification function.

[0113] When the distance between the microphone and the loudspeaker is greater than the preset howling suppression distance threshold, it indicates that the risk of howling has decreased. At this time, the gain of the microphone can be adjusted to a preset second value (1 or the default gain value of the system) to restore the normal sound amplification function.

[0114] If, after restoring the normal sound amplification function, the distance between the microphone and the loudspeaker decreases again to be less than the howling suppression distance threshold, the gain is dynamically adjusted again to reduce the risk of howling.

[0115] In the above optional embodiments, the distance between the microphone and the loudspeaker is detected in real time, and the gain is automatically adjusted according to a preset rule. The entire gain adjustment process is automatic and does not require manual intervention. It can effectively suppress the occurrence of howling while ensuring the sound amplification quality.

[0116] The following combines Figure 2 As shown, the howling suppression method of the present application is described. The howling suppression method is a dynamic process, including the following steps:

[0117] Step 1: Pick up the sound signal s0 through the microphone.

[0118] During normal operation, the microphone continuously picks up the surrounding sound waves and converts them into electrical signals, that is, the sound signal s0. The sound signal s0 contains all the sound information in the environment, including human voices, environmental noises, and the sounds that may be broadcast by the speaker.

[0119] Step 2: Modulate the pulse signal generated by the microphone to obtain a pulse modulation signal p0.

[0120] The microphone itself generates some continuous pulse signals during operation. Although these pulse signals are weak, they can be used for distance measurement. In order to distinguish the pulse signal from the normal sound pickup signal, the pulse signal needs to be modulated. The modulation process is to embed the pulse signal onto a specific carrier frequency, so that it is clearly distinguishable from the normal sound pickup signal in the frequency domain. The obtained pulse modulation signal p0 after modulation will be used for subsequent distance measurement.

[0121] Step 3: Shift the frequency of the pulse modulation signal to the target frequency band.

[0122] If the pulse signal is directly mixed with the normal pick-up signal of the microphone, signal confusion may occur due to similar frequency components, making it difficult to accurately extract the pulse signal for subsequent processing. Shifting the frequency of the pulse modulation signal to the target frequency band is to ensure its separation from the normal pick-up signal in the frequency domain, which can not only avoid interference of the modulation signal on the normal pick-up signal, but also facilitate subsequent signal processing.

[0123] The target frequency band is usually selected within the frequency band that cannot be perceived by the human ear, such as above 20 kHz. The carrier frequency of the frequency-shifted pulse modulation signal p0 is denoted as f0.

[0124] Step 4: Filter the normal pick-up signal s0 of the microphone to obtain the filtered signal s1.

[0125] While processing the pulse modulation signal, it is also necessary to filter the normal pick-up signal s0 of the microphone. The purpose of filtering is to remove high-frequency noise and interference components in the pick-up signal to improve the accuracy and stability of subsequent signal processing.

[0126] In the embodiment of the present application, a low-pass filter is applied to the normal pick-up signal s0 of the microphone. The cut-off frequency of the low-pass filter for the pick-up signal is lower than the carrier frequency f0 of the pulse modulation signal to ensure that the filtered signal s1 does not contain the components of the modulation signal.

[0127] Step 5: Combine the pulse modulation signal shifted to the target frequency band with the filtered signal s1 to obtain a combined signal, and output the combined signal to the loudspeaker for playback.

[0128] After modulation and filtering, the pulse modulation signal p0 is combined with the filtered signal s1 to obtain a combined signal. The combined signal contains both the information of the normal pick-up signal and the pulse modulation signal for distance measurement. The combined signal is output to the loudspeaker for playback. At this time, the microphone will pick up the sound signal broadcast by the loudspeaker again, including the pulse modulation signal part in the combined signal.

[0129] Step 6: The microphone receives the mixed signal played by the loudspeaker, and demodulates the mixed signal according to the carrier frequency f0 of the pulse modulation signal to obtain the pulse demodulation signal p1.

[0130] When the microphone receives the mixed signal broadcast by the loudspeaker, it will contain the sound signal broadcast by the speaker and possible reflected signals. To extract the pulse modulation signal part for distance measurement, it is necessary to demodulate the mixed signal. The demodulation process is to perform band-pass filtering on the mixed signal according to the carrier frequency f0 of the pulse modulation signal, and extract the frequency band signal centered on f0. After demodulating this frequency band signal, the pulse demodulation signal p1 can be obtained.

[0131] It should be noted that when the microphone is close to the loudspeaker (i.e., the distance at which howling may occur), the sound signal picked up by the microphone will contain more sound broadcast by the speaker. At this time, the pulse demodulation signal p1 obtained by demodulation will be more obvious and stable, which is beneficial to subsequent distance measurement and gain adjustment.

[0132] Step 7: Calculate the distance D between the microphone and the loudspeaker according to the pulse demodulation signal p1.

[0133] The pulse demodulation signal p1 is obtained by the pulse modulation signal p0 being played by the speaker, propagating a certain distance, and then being picked up and demodulated by the microphone again. In this process, the propagation time (or round-trip time) of the pulse signal is proportional to the distance D between the microphone and the loudspeaker. Therefore, the distance D can be calculated by measuring the interval between the pulse peaks in the pulse demodulation signal p1.

[0134] The embodiment of the present application can extract the time information of the pulse peak according to p1, and calculate the distance D according to the known signal propagation speed (such as the speed of sound).

[0135] Step 8: Dynamically adjust the gain of the output signal of the microphone according to the distance D to suppress howling.

[0136] Since the pulse demodulation signal p1 is continuously calculated, the distance is also continuously calculated. After obtaining the distance D between the microphone and the loudspeaker, the gain of the output signal of the microphone can be dynamically adjusted according to this distance.

[0137] When the distance is less than the preset howling suppression distance threshold (for example, 1 meter), it indicates that the risk of howling is relatively high and howling suppression operation needs to be performed. At this time, the gain of the microphone should be appropriately reduced to reduce feedback. On the contrary, when the distance D is large, the gain can be appropriately increased to ensure sound quality.

[0138] The process of dynamically adjusting the gain can be implemented by a gain controller. The gain controller can adjust the gain coefficient k (k < 1) in real time according to the value of the distance D, and apply the adjusted gain to the filtered signal s1 to obtain a new signal s2 (s2 = k * s1). Then s2 is sent to the loudspeaker for playback. Among them, the value of the gain coefficient k should be proportional to the distance D, that is, the smaller the distance, the lower the gain. When the distance is less than the preset howling suppression distance threshold (such as approaching 0 meter), the value of k can be set to 0 to achieve complete howling suppression (100% howling suppression).

[0139] In practical applications, to achieve smooth gain adjustment and avoid the impact of sudden gain changes on sound quality, a gradual gain adjustment strategy can be adopted. That is, when the distance D changes, instead of immediately changing the value of the gain coefficient k, the value of k is gradually adjusted at a certain rate until the target gain is reached. This can ensure the continuity and stability of sound quality.

[0140] According to a preset howling suppression distance threshold, it can be determined whether to perform or not perform the howling suppression operation. The howling suppression method can be any effective method, but except for the means of directly reducing the gain k to 0, other howling suppression methods cannot achieve a complete suppression effect. Therefore, when the distance is less than the preset gain suppression distance threshold, directly setting the gain k to 0 can achieve complete suppression. The reason is that setting k to 0 actually shuts down the amplification function at the same time, so it must be implemented when the distance is close enough, and once the distance is increased, the normal amplification function can be automatically restored. This can avoid howling caused by too close a distance and maintain the amplification effect at a normal distance.

[0141] The howling suppression of this application can reach 100%. The reason is that after obtaining the distance between the microphone and the loudspeaker, the gain of the microphone can be adjusted according to this distance. For example, even in an extreme case where the microphone is directly attached to the diaphragm of the loudspeaker, the gain of the microphone can be set to 0, then there is no positive feedback at all, and it is impossible to generate howling, thus achieving complete howling suppression. In addition, in traditional amplification devices, to obtain the specific distance between the microphone and the loudspeaker, an effective ranging method must be used. Without adding additional devices and without deliberately using a ranging method, the microphone end of this application can calculate the distance between the two through the sound broadcast by the loudspeaker, and then dynamically adjust the gain of the microphone according to the distance to achieve the effect of suppressing howling.

[0142] In the prior art, the audible sound frequency band broadcast by the speaker is directly collected for judgment, and no additional signal is added to the sound broadcast by the speaker, so there is no modulation processing of the additional signal. This application modulates the pulse signal generated by the microphone and shifts the frequency to a frequency band inaudible to the human ear, and no processing is performed on the frequency band audible to the human ear, so there is no distortion in the listening experience.

[0143] In addition, the prior art determines the distance of the speaker based on the sound intensity collected by the microphone. However, the sound intensity is affected by many external environmental factors. For example, when there is a sound-absorbing object or a moving sound-reflecting object between the speaker and the microphone, the sound intensity collected by the microphone will change, resulting in a misjudgment that the distance between the speaker and the microphone is changing. Moreover, the attenuation degree of sound is different when the speaker and the microphone are placed in different environments. Therefore, the prior art cannot accurately measure the distance. This application uses pulse modulation, which intermittently emits a very short sound in a frequency band that is inaudible to the human ear. The time it takes for the sound to leave the speaker and reach the microphone, the time delay, is directly related to the distance and is completely independent of the surrounding environment. Therefore, the distance can be accurately measured.

[0144] The complexity of the algorithm of this application is approximately equivalent to that of the frequency shift algorithm, and there is no need to use a chip with high computing power.

[0145] Figure 3 It is a functional module diagram of the howling suppression device provided by an embodiment of this application.

[0146] In some embodiments, the howling suppression device 30 may include multiple functional modules composed of program code segments. The program code of each program segment in the howling suppression device 30 can be stored in the memory of the sound amplification device and executed by at least one processor to perform the function of howling suppression (see the detailed Figure 1 description).

[0147] In this embodiment, the howling suppression device 30 can be divided into multiple functional modules according to the functions it performs. The functional modules may include: a receiving module 301, a demodulation module 302, a calculation module 303, and a suppression module 304. The module referred to in this application means a series of computer-readable instruction segments that can be executed by at least one processor and can complete a fixed function, and is stored in the memory. In this embodiment, the functions of each module will be described in detail in subsequent embodiments.

[0148] The receiving module 301 is configured to receive the mixed signal of the sound played by the loudspeaker through the microphone. Among them, the mixed signal includes: a pulse modulation signal obtained by modulating the pulse signal generated by the microphone and shifting the frequency to the target frequency band, and the normal sound pickup signal of the microphone;

[0149] The demodulation module 302 is configured to demodulate the mixed signal according to the pulse modulation signal to obtain a pulse demodulation signal;

[0150] The calculation module 303 is configured to calculate the distance between the microphone and the loudspeaker according to the pulse demodulation signal;

[0151] The suppression module 304 is configured to dynamically adjust the current gain of the microphone according to the distance to suppress howling.

[0152] It should be understood that the various variations and specific embodiments in the howling suppression method provided in the above embodiments are equally applicable to the howling suppression device in this embodiment. Through the detailed description of the foregoing howling suppression method, those skilled in the art can clearly know the implementation process of the howling suppression device in this embodiment. For the sake of brevity of the specification, it will not be elaborated here.

[0153] The embodiment of the present application further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, all or part of the steps of the howling suppression method are implemented.

[0154] Refer to Figure 4 As shown, it is a schematic structural diagram of a sound amplification device provided by an embodiment of the present application. In a preferred embodiment of the present application, the sound amplification device 4 includes a memory 401, at least one processor 402, at least one communication bus 403, a microphone 404, and a loudspeaker 405.

[0155] Those skilled in the art should understand that Figure 4 the structure of the shown sound amplification device does not constitute a limitation on the embodiments of the present application. The sound amplification device 4 may further include more or fewer other hardware or software than shown, or different component arrangements.

[0156] In some embodiments, the sound amplification device 4 is a device capable of automatically performing numerical calculations and / or information processing according to pre-set or stored instructions. Its hardware includes, but is not limited to, a microprocessor, an application-specific integrated circuit, a programmable gate array, a digital signal processor, and an embedded device, etc. The sound amplification device 4 may further include a client device, and the client device includes, but is not limited to, any electronic product that can perform human-computer interaction with the client in ways such as a keyboard, a mouse, a remote control, a touchpad, or a voice control device. For example, a personal computer, a tablet computer, a smart phone, a digital camera, etc.

[0157] It should be noted that the sound amplification device 4 is only an example, and other existing or future possible electronic products that can be adapted to the present application should also be included within the protection scope of the present application and are hereby incorporated by reference.

[0158] In some embodiments, a computer program is stored in the memory 401. When the computer program is executed by the at least one processor 402, all or part of the steps in the described howling suppression method are implemented. The memory 401 includes a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), a one-time programmable read-only memory (OTPROM), an electrically-erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc memory, a magnetic disk memory, a tape memory, or any other computer-readable medium capable of carrying or storing data. Further, the computer-readable storage medium mainly includes a program storage area and a data storage area. Among them, the program storage area can store an operating system, application programs required for at least one function, etc.

[0159] In some embodiments, the at least one processor 402 is the control core (Control Unit) of the sound amplification device 4, connecting various components of the entire sound amplification device 4 through various interfaces and lines. By running or executing the programs or modules stored in the memory 401, and calling the data stored in the memory 401, various functions of the sound amplification device 4 are executed and data is processed. For example, when the at least one processor 402 executes the computer program stored in the memory, all or part of the steps in the howling suppression method described in the embodiments of the present application are implemented; or all or part of the functions of the howling suppression device are implemented. The at least one processor 402 may be composed of integrated circuits. For example, it may be composed of a single packaged integrated circuit, or may be composed of multiple integrated circuits with the same or different functions packaged, including a combination of one or more central processing units (CPUs), microprocessors, digital processing chips, graphics processors, and various control chips.

[0160] In some embodiments, the at least one communication bus 403 is configured to enable connection communication between the memory 401 and the at least one processor 402, etc. Although not shown, the sound amplification device 4 may further include a power source (such as a battery) for powering each component. Preferably, the power source can be logically connected to the at least one processor 402 through a power management device, so as to implement functions such as management of charging, discharging, and power consumption management through the power management device. The power source may further include any components such as one or more DC or AC power sources, a recharge device, a power failure detection circuit, a power converter or inverter, a power status indicator, etc. The sound amplification device 4 may further include various sensors, a Bluetooth module, a Wi-Fi module, etc., which will not be elaborated here.

[0161] The integrated unit implemented in the form of a software functional module as described above can be stored in a computer-readable storage medium. The above software functional module is stored in a storage medium and includes several instructions for causing a sound amplification device (which may be a personal computer, a sound amplification device, or a network device, etc.) or a processor to execute a part of the methods described in various embodiments of the present application.

[0162] In several embodiments provided by the present application, it should be understood that the disclosed device and method can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the modules is only a logical function division, and there may be other division methods in actual implementation.

[0163] The modules described as separate components may or may not be physically separated, and the components shown as modules may or may not be physical units. They may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

Claims

1. A howling suppression method, characterized in that: The method comprises: Receiving a mixed signal of the sound played by the loudspeaker through the microphone, wherein the mixed signal includes: a pulse modulation signal obtained by modulating the pulse signal generated by the microphone and then shifting the frequency to the target frequency band, and a normal sound pickup signal of the microphone; Demodulating the mixed signal according to the pulse modulation signal to obtain a pulse demodulation signal; calculating the distance between the microphone and the loudspeaker according to the pulse demodulation signal; The current gain of the microphone is dynamically adjusted according to the distance to suppress howling.

2. The howling suppression method according to claim 1, characterized in that: The demodulating the mixed signal according to the pulse modulation signal to obtain a pulse demodulation signal comprises: Filtering the mixed signal and extracting a frequency band signal centered on the carrier frequency of the pulse modulation signal; The extracted frequency band signal is demodulated to obtain a pulse demodulation signal.

3. The howling suppression method according to claim 1, characterized in that: The calculating the distance between the microphone and the loudspeaker according to the pulse demodulation signal comprises: Determining a first moment at which the microphone outputs a pulse signal to the loudspeaker; determining a fixed delay within the loudspeaker; identifying a second time instant of a pulse peak in the pulse demodulated signal; The distance between the microphone and the loudspeaker is calculated according to the delay, the first moment, the second moment and the sound propagation speed.

4. The howling suppression method according to claim 1, characterized in that: The dynamically adjusting the current gain of the microphone according to the distance to suppress the howling includes: comparing the distance with a preset howling suppression distance threshold and a preset gain suppression distance threshold; When the distance is less than the preset howling suppression distance threshold, adjusting the current gain of the microphone according to the distance, the gain being proportional to the distance; When the distance is less than or equal to the preset gain suppression distance threshold, adjusting the current gain of the microphone to a preset first value to achieve complete suppression of howling; The preset howling suppression distance threshold is greater than the preset gain suppression distance threshold.

5. The howling suppression method according to claim 4, characterized in that: The method also includes. When the distance is greater than the preset howling suppression distance threshold, the current gain of the microphone is adjusted to a preset second value to restore the normal sound amplification function.

6. The howling suppression method according to claim 1, characterized in that: The method further comprises: Filtering the normal sound pickup signal of the microphone to obtain a filtered signal; The pulse modulated signal is combined with the filtered signal.

7. The howling suppression method according to claim 6, characterized in that: The cut-off frequency for filtering the normal sound pickup signal of the microphone is lower than the carrier frequency of the pulse modulation signal.

8. A howling suppression device, characterized in that: The device comprises: A receiving module, used for receiving a mixed signal of sound played by a loudspeaker through a microphone, wherein the mixed signal includes: a pulse modulation signal obtained by modulating a pulse signal generated by the microphone and then frequency shifting it to a target frequency band, and a normal sound pickup signal of the microphone; A demodulation module, used for demodulating the mixed signal according to the pulse modulation signal to obtain a pulse demodulation signal; A calculation module, used for calculating the distance between the microphone and the loudspeaker according to the pulse demodulation signal; The suppression module is used to dynamically adjust the current gain of the microphone according to the distance to suppress howling.

9. A sound amplification device, characterized in that: The sound amplification device comprises a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the howling suppression method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the howling suppression method according to any one of claims 1 to 7 are implemented.

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