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

Abstract

The application relates to the audio field and provides a howling suppression method and device, a sound amplification equipment and a storage medium. A mixed signal of sound played by a sound amplifier is received by a microphone. The mixed signal comprises a pulse modulation signal obtained by modulating a pulse signal generated by the microphone and shifting the frequency to a target frequency range, and a normal pickup signal of the microphone. The mixed signal is demodulated according to the pulse modulation signal to obtain a pulse demodulation signal. The distance between the microphone and the sound amplifier is calculated according to the pulse demodulation signal. The current gain of the microphone is dynamically adjusted according to the distance to suppress howling. The pulse modulation and demodulation technology can be used to accurately calculate the distance between the microphone and the sound amplifier, and the gain of the microphone is dynamically adjusted according to the distance, so that the howling phenomenon can be effectively suppressed.

Description

Technical Field

[0001] This application relates to the field of audio technology, and in particular to a method, apparatus, amplification device, and storage medium for suppressing howling. Background Technology

[0002] Feedback, also known as self-excited oscillation or feedback howling, typically occurs when a sound signal picked up by a microphone is amplified and played through a speaker, only to be picked up and amplified again by the microphone, forming a closed feedback loop. When the gain of this loop exceeds a certain threshold, the system produces a loud screeching sound, i.e., howling. Howling not only affects the sound quality and effect of the amplification system but can also cause discomfort to listeners.

[0003] In the existing technology, there are algorithms for suppressing feedback from microphone amplification, but none of these algorithms can completely suppress feedback. Summary of the Invention

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

[0005] A first aspect of this application provides a method for suppressing howling, the method comprising:

[0006] The microphone receives a mixed signal of sound played from an amplifier, wherein the mixed signal includes: a pulse modulation signal obtained by modulating and shifting the pulse signal generated by the microphone to a target frequency band, and the normal pickup signal of the microphone;

[0007] The mixed signal is demodulated according to the pulse modulation signal to obtain the pulse demodulated signal;

[0008] Calculate the distance between the microphone and the loudspeaker based on the pulse demodulation signal;

[0009] The microphone's current gain is dynamically adjusted based on the distance to suppress feedback.

[0010] Optionally, demodulating the mixed signal based on the pulse modulation signal to obtain the pulse demodulated signal includes:

[0011] The mixed signal is filtered, and the frequency band signal centered on the carrier frequency of the pulse modulation signal is extracted;

[0012] The extracted frequency band signal is demodulated to obtain a pulse demodulated signal.

[0013] Optionally, calculating the distance between the microphone and the loudspeaker based on 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] The second moment for identifying the pulse peak in the pulse demodulated signal;

[0017] The distance between the microphone and the loudspeaker is calculated based on the delay, the first moment, the second moment, and the speed of sound propagation.

[0018] Optionally, dynamically adjusting the current gain of the microphone based on the distance to suppress feedback 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, the current gain of the microphone is adjusted 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, the current gain of the microphone is adjusted to a preset first value to completely suppress feedback.

[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 feedback suppression distance threshold, the current gain of the microphone is adjusted to a preset second value to restore normal amplification function.

[0025] Optionally, the method further includes:

[0026] The normal pickup signal from the microphone is filtered to obtain a filtered signal;

[0027] The pulse modulation signal and the filtered signal are combined to obtain a combined signal;

[0028] The combined signal is output to the loudspeaker for playback.

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

[0030] A second aspect of this application provides a whistling suppression device, the device comprising:

[0031] A receiving module is used to receive 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 shifting it to a target frequency band, and a normal pickup signal of the microphone;

[0032] The demodulation module is used to demodulate the mixed signal according to the pulse modulation signal to obtain a pulse demodulated signal;

[0033] The calculation module is used to calculate the distance between the microphone and the loudspeaker based on the pulse demodulation signal;

[0034] A suppression module is used to dynamically adjust the current gain of the microphone based on the distance to suppress feedback.

[0035] A third aspect of this application provides a loudspeaker device, the loudspeaker device including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the howling suppression method.

[0036] A fourth aspect of this application provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the whistling suppression method.

[0037] This application receives a mixed signal of sound played from a loudspeaker via a microphone. The mixed signal includes: a pulse-modulated signal obtained by modulating and shifting a pulse signal generated by the microphone to a target frequency band, and the microphone's normal pickup signal. Modulating the microphone's pulse signal and shifting its frequency to the target frequency band gives the modulated pulse signal specific frequency characteristics, allowing demodulation of the mixed signal based on the pulse-modulated signal to obtain a pulse-demodulated signal. The distance between the microphone and the loudspeaker is then calculated based on the pulse-demodulated signal. Finally, the microphone's current gain is dynamically adjusted based on the distance to suppress feedback. This application utilizes pulse modulation and demodulation technology to accurately calculate the distance between the microphone and the loudspeaker and dynamically adjust the microphone's gain based on the distance, thereby effectively suppressing feedback. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a flowchart illustrating the howling suppression method provided in the embodiments of this application.

[0040] Figure 2 This is a schematic diagram of the data flow of the howling suppression method provided in the embodiments of this application.

[0041] Figure 3 This is a functional block diagram of the whistling suppression device provided in the embodiments of this application.

[0042] Figure 4 This is a schematic diagram of the structure of the loudspeaker provided in the embodiments of this application. Detailed Implementation

[0043] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0044] In modern audio technology, microphone amplification systems are widely used in various occasions, such as speeches, meetings, performances, and entertainment activities. As a key device for sound acquisition, the microphone converts sound signals into electrical signals, which are then amplified and processed before being played back through loudspeakers. However, a common and unpleasant problem during microphone amplification is feedback.

[0045] Feedback, also known as self-excited oscillation or feedback howling, typically occurs when a sound signal picked up by a microphone is amplified and played through a speaker, only to be picked up and amplified again by the microphone, forming a closed feedback loop. When the gain of this loop exceeds a certain threshold, the system produces a loud screeching sound, i.e., howling. Howling not only affects the sound quality and effect of the amplification system but can also cause discomfort to listeners.

[0046] Existing technologies include frequency shifting algorithms, equalizer algorithms, squelch gate algorithms, and echo cancellation algorithms to suppress microphone feedback. However, frequency shifting algorithms have limited effectiveness in suppressing feedback and can cause sound distortion. Equalizers (EQ) can easily cause sound distortion and require pre-calibration based on the usage environment and equipment; moreover, they cannot achieve 100% suppression. Squelch gate algorithms can completely suppress feedback in some cases, but the sound has a jerky, switching quality, and if the volume picked up by the microphone exceeds a certain threshold, there is no suppression effect at all, easily producing abrupt feedback. Echo cancellation algorithms can achieve deep suppression, but the algorithms are complex and computationally intensive, requiring the use of high-cost, high-end chips; they also cannot guarantee 100% suppression, and sound distortion may still occur.

[0047] In order to completely suppress howling, this application provides a howling suppression method, apparatus, amplification device and storage medium.

[0048] Figure 1 This is a flowchart illustrating the howling suppression method provided in an embodiment of this application. The howling suppression method includes the following steps.

[0049] S11 receives a mixed signal of sound played through a loudspeaker via a microphone.

[0050] The aforementioned feedback suppression method can be applied to loudspeaker equipment, which includes a microphone and a megaphone. A microphone, also known as a transducer, is a transducer that converts sound into electrical signals. A megaphone, also known as a loudspeaker, is a device that converts electrical energy into sound energy. The microphone is responsible for collecting sound, which is then processed and amplified by internal circuitry, and finally played back by the loudspeaker or megaphone.

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

[0052] The microphone itself generates a continuous pulse signal p0. The pulse signal p0 is a periodic pulse signal with adjustable pulse width and interval. The pulse signal p0 generated by the microphone is modulated and shifted to the target frequency band to obtain a pulse modulated signal. This modulated signal is then combined with the microphone's normal pickup signal s0 to obtain a combined signal. Finally, the combined signal is output to the amplifier for playback.

[0053] Modulating and shifting the pulse signal generated by the microphone to the target frequency band means modulating the pulse signal generated by the microphone and shifting it to a frequency band that is imperceptible to the human ear. A frequency band imperceptible to the human ear can refer to the ultrasonic frequency band above 30kHz. Shifting the modulated pulse signal to the target frequency band yields a modulated signal with a carrier frequency of f0.

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

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

[0056] In an optional implementation, the method further includes:

[0057] The normal pickup signal from the microphone is filtered to obtain a filtered signal;

[0058] The pulse modulation signal and the filtered signal are combined to obtain a combined signal;

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

[0060] The normal microphone pickup signal s0 is low-pass filtered to obtain the filtered audio signal s1 (i.e., the filtered signal). Low-pass filtering is a filtering method that allows only low-frequency signals to pass while attenuating high-frequency signals. Low-pass filtering of the normal microphone pickup signal 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] Specifically, the cutoff frequency for filtering the pickup signal is lower than the carrier frequency of the pulse modulation signal. The cutoff frequency is the highest frequency that the filter allows to pass through. Signals at and near the carrier frequency are considered high-frequency components. Setting the filter's cutoff frequency below the carrier frequency of the pulse modulation signal ensures that signals at and near the carrier frequency are effectively attenuated or removed, thereby improving the purity and clarity of the audio signal.

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

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

[0064] S12, Demodulate the mixed signal according to the pulse modulation signal to obtain a pulse demodulated signal.

[0065] Demodulation is the inverse process of modulation, and its purpose is to recover the original information from the modulated signal.

[0066] Known characteristics of pulse modulation signals (such as pulse shape, width, and modulation method) can be used as a reference to analyze and process mixed signals. By identifying the parts of the mixed signal that match the characteristics of the pulse modulation signal, the pulse modulation signal can be separated, and the original information can be further extracted. After demodulation processing, the pulse modulation signal separated from the mixed signal is the pulse demodulated signal.

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

[0068] In an optional implementation, demodulating the mixed signal based on the pulse modulation signal to obtain a pulse demodulated signal includes:

[0069] The mixed signal is filtered, and the frequency band signal centered on the carrier frequency of the pulse modulation signal is extracted;

[0070] The extracted frequency band signal is demodulated to obtain a pulse demodulated signal.

[0071] The purpose of using a bandpass filter to perform bandpass filtering on a mixed signal is to extract the frequency band signal centered on the carrier frequency of the pulse modulation signal from the mixed signal.

[0072] A bandpass filter allows signals within a specific frequency range to pass through while attenuating signals at other frequencies. In this embodiment, the center frequency of the filter is set to the carrier frequency of the pulse-modulated signal, thereby allowing signal components with frequencies close to that frequency to pass through.

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

[0074] S13, calculate the distance between the microphone and the loudspeaker based on the pulse demodulation signal.

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

[0076] By comparing the transmitted pulse signal with 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 travel from the microphone to the amplifier. Finally, using the relationship between the speed of sound and time delay, i.e., distance = speed × time, the distance between the microphone and the amplifier can be calculated.

[0077] To obtain accurate distance measurement, in one optional implementation, calculating the distance between the microphone and the loudspeaker based on 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] The second moment for identifying the pulse peak in the pulse demodulated signal;

[0081] The distance between the microphone and the loudspeaker is calculated based on the delay, the first moment, the second moment, and the speed of sound propagation.

[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. The time point t0 is recorded as the first moment.

[0083] After receiving a pulse signal p0, the loudspeaker begins playing the signal only after a fixed internal delay Ta. This internal delay can be determined by various factors such as the loudspeaker's circuit processing and speaker response, and is usually known or calibrable in practical applications.

[0084] The microphone then receives a mixed signal containing the sound played from the amplifier. To extract information about 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 demodulated pulse signal), the time t1 of the pulse peak (denoted as the second moment) is accurately identified by detecting the zero-crossing or peak point of the signal. Time t1 represents the exact time when the microphone receives the pulse signal played by the amplifier.

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

[0086] The above-described optional implementation achieves high-precision distance calculation by accurately measuring the transmitted pulse time t0 and the received pulse peak time t1, combined with the amplifier's internal delay Ta and the sound propagation speed s. Identifying the pulse peak time using the demodulated pulse signal effectively reduces the impact of noise and interference on the measurement results, improving measurement reliability. This provides accurate distance information for feedback suppression, thereby helping to optimize the performance of the sound reinforcement system and reduce feedback phenomena.

[0087] In an optional implementation, the current environmental conditions can be obtained, and the sound propagation speed can be corrected based on these 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 transmitted pulse time t0, the received pulse peak time t1, the loudspeaker's internal delay Ta, and the corrected sound propagation speed s. The preset correction formula or model is: sound speed = (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. Thus, this application can be applied to distance measurement under different environmental and conditions, requiring only appropriate correction of the sound propagation speed s.

[0088] S14, dynamically adjust the current gain of the microphone according to the distance to suppress feedback.

[0089] Feedback typically occurs when a microphone picks up sound amplified by a loudspeaker and amplifies it again, creating a positive feedback loop. Adjusting the microphone gain can control the strength of the input signal, thus preventing feedback.

[0090] In an optional implementation, before dynamically adjusting the current gain of the microphone based on the distance, the method may further include:

[0091] Whether to perform a howling suppression operation is determined based on the distance.

[0092] The distance between the microphone and the loudspeaker is one of the important factors affecting the risk of feedback. The closer the distance, the higher the risk of feedback; the farther the distance, the lower the risk of feedback. Therefore, before dynamically adjusting the microphone's current gain, it is necessary to first determine whether there is a risk of feedback under the current conditions based on the measured distance, that is, to determine whether feedback suppression operations need to be performed.

[0093] By implementing pre-emptive judgment steps, feedback suppression operations can be avoided unnecessarily, thus preventing any impact on the intensity and quality of the amplification and improving the overall system efficiency and sound quality. Dynamically adjusting microphone gain may consume system resources. By determining whether feedback suppression is necessary, these resources can be conserved, extending the system's lifespan.

[0094] In an optional implementation, determining whether to perform a howling suppression operation based on the distance includes:

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

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

[0097] If the distance is greater than the preset howling distance threshold, it is determined that the howling suppression operation will not be performed.

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

[0099] The calculated distance is compared with a preset feedback distance threshold. If the distance is less than or equal to the preset feedback distance threshold, it indicates a high risk of feedback at the current distance. Therefore, it is determined that feedback suppression operation needs to be performed, such as dynamically adjusting the microphone gain to reduce the strength of the input signal, thereby avoiding feedback. If the distance is greater than the preset feedback distance threshold, it indicates a low risk of feedback at the current distance. Therefore, it is determined that feedback suppression operation does not need to be performed to save resources and avoid unnecessary adjustments.

[0100] The above-described optional implementation scheme achieves howling suppression based on the relationship between distance and howling risk, and the principle of dynamically adjusting gain. When the distance is short and the howling risk is high, reducing the gain can decrease the strength of the input signal, thereby preventing howling. When the distance is long and the howling risk is low, such adjustments are not necessary.

[0101] In an optional implementation, dynamically adjusting the microphone's current gain based on the distance to suppress feedback 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, the current gain of the microphone is adjusted 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, the current gain of the microphone is adjusted to a preset first value to completely suppress feedback.

[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 used to determine whether howling suppression needs to be started and whether howling needs to be completely suppressed, respectively.

[0107] When the distance is less than the preset feedback suppression distance threshold, it indicates a risk of feedback at the current distance. To reduce the feedback risk, the current gain of the microphone needs to be adjusted. By adjusting the gain of the microphone output signal, the intensity of the input signal can be adjusted. Since feedback usually occurs when the microphone is too close to the amplifier (or speaker), the microphone easily picks up the sound amplified by the speaker and amplifies it again, forming a positive feedback loop. To suppress feedback, the gain of the microphone needs to be reduced to reduce the intensity of the input signal. As the distance continues to decrease, the risk of feedback continues to increase, so the gain can be reduced accordingly to further reduce the intensity of the input signal. In this embodiment, the gain k can be determined based on the calculated distance D, where the value of gain k is proportional to the distance D. That is, the smaller the distance, the lower the gain. The gain k is applied to the filtered sound signal s1 to obtain the adjusted sound signal s2, i.e., s2 = k * s1, and the adjusted sound signal s2 is output to the amplifier for playback. By adjusting the gain to be proportional to the distance, the risk of feedback can be effectively reduced while maintaining sound quality.

[0108] When the distance is less than or equal to the preset gain suppression distance threshold, it indicates that the risk of feedback at the current distance is very high. To completely avoid feedback, the microphone's current gain needs to be adjusted to a preset first value (the preset first value can be 0). This means completely shutting down the microphone, thus achieving complete feedback suppression. Completely shutting down the microphone means completely stopping the amplification function.

[0109] The reason for setting the feedback suppression distance threshold to be greater than the gain suppression distance threshold is to provide a buffer. When the distance decreases to the feedback suppression distance threshold, the risk of feedback is reduced by adjusting the gain, rather than immediately shutting off the microphone. This ensures that as the feedback risk gradually increases, there is enough time to smoothly adjust the gain, avoiding the impact of sudden gain changes on sound quality. Only when the distance decreases to or below the gain suppression distance threshold will more extreme measures be taken, namely completely shutting off the microphone, to ensure that feedback is completely suppressed.

[0110] The above-described optional implementation, by refining the gain adjustment strategy and setting two preset distance thresholds (feedback suppression distance threshold and gain suppression distance threshold), allows for different gain adjustment strategies at different distances, achieving smooth gain adjustment and reliable feedback suppression. This reduces the risk of feedback while maintaining good sound quality. In extreme cases, completely shutting down the microphone can ensure complete feedback suppression, improving the system's flexibility and reliability.

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

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

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

[0114] If, after the normal amplification function is restored, the distance between the microphone and the amplifier decreases again to below the feedback suppression distance threshold, the gain will be dynamically readjusted to reduce the risk of feedback.

[0115] The optional implementation described above detects the distance between the microphone and the amplifier in real time and automatically adjusts the gain according to preset rules. The entire gain adjustment process is automatic and requires no manual intervention. This effectively suppresses feedback while ensuring sound amplification quality.

[0116] The following is combined Figure 2 The following describes the howling suppression method of this application. The howling suppression method is a dynamic process, including the following steps:

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

[0118] During normal operation, the microphone continuously collects ambient sound waves and converts them into electrical signals, namely sound signals s0. Sound signal s0 contains all sound information in the environment, including human voices, ambient noise, and sounds that may be emitted by speakers.

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

[0120] The microphone itself generates continuous pulse signals during operation. Although these pulse signals are weak, they can be used for distance measurement. To distinguish these pulse signals from the normal audio signal, they need to be modulated. The modulation process involves embedding the pulse signal into a specific carrier frequency, thereby clearly distinguishing it from the normal audio signal in the frequency domain. The resulting modulated pulse signal p0 will be used for subsequent distance measurement.

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

[0122] If the pulse signal is directly mixed with the microphone's normal pickup signal, signal confusion may occur due to the similarity of frequency components, making it difficult to accurately extract the pulse signal for subsequent processing. Shifting the pulse modulation signal to the target frequency band ensures its separation from the normal pickup signal in the frequency domain. This not only avoids interference from the modulation signal to the normal pickup signal but also facilitates subsequent signal processing.

[0123] The target frequency band is usually chosen within a frequency range imperceptible to the human ear, such as above 20kHz. The carrier frequency of the frequency-shifted pulse modulation signal p0 is denoted as f0.

[0124] Step 4: Filter the normal microphone pickup signal s0 to obtain the filtered signal s1.

[0125] While processing the pulse modulation signal, it is also necessary to filter the microphone's normal pickup signal s0. The purpose of filtering is to remove high-frequency noise and interference components from the pickup signal, thereby improving the accuracy and stability of subsequent signal processing.

[0126] In this embodiment, the normal microphone pickup signal s0 is low-pass filtered. The cutoff frequency of the low-pass filter is lower than the carrier frequency f0 of the pulse modulation signal to ensure that the filtered signal s1 does not contain any modulated signal components.

[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-modulated signal p0 and the filtered signal s1 are combined to obtain the combined signal. The combined signal contains information from the normal audio signal and also embeds the pulse-modulated signal used for distance measurement. The combined signal is output to a loudspeaker for playback, at which point the microphone will again pick up the audio signal played by the loudspeaker, including the pulse-modulated signal portion of the combined signal.

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

[0130] When the microphone receives the mixed signal broadcast from the loudspeaker, it contains the sound signal from the loudspeaker and possible reflected signals. To extract the pulse-modulated signal portion used for distance measurement, the mixed signal needs to be demodulated. The demodulation process involves bandpass filtering the mixed signal based on the carrier frequency f0 of the pulse-modulated signal and extracting the frequency band centered at f0. Demodulating this frequency band yields the pulse-demodulated signal p1.

[0131] It's important to note that when the microphone is close to the loudspeaker (i.e., at a distance that could cause feedback), the sound signal picked up by the microphone will contain a significant portion of the sound emitted by the loudspeaker. In this case, the demodulated pulse signal p1 will be more pronounced and stable, which is beneficial for subsequent distance measurement and gain adjustment.

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

[0133] The pulse demodulated signal p1 is obtained by the microphone after the pulse modulated signal p0 is played through the speaker, propagates a certain distance, and is then picked up and demodulated 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 speaker. Therefore, the distance D can be calculated by measuring the interval between the pulse peaks in the pulse demodulated signal p1.

[0134] In this embodiment, the timing information of the pulse peak can be extracted from p1, and the distance D can be calculated based on the known signal propagation speed (such as the speed of sound).

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

[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 amplifier, the gain of the microphone's output signal can be dynamically adjusted based on this distance.

[0137] When the distance is less than the preset feedback suppression distance threshold (e.g., 1 meter), it indicates a high risk of feedback, requiring feedback suppression. In this case, the microphone gain should be appropriately reduced to decrease feedback. Conversely, when the distance D is large, the gain can be appropriately increased to ensure sound quality.

[0138] The dynamic adjustment of gain can be achieved through a gain controller. The gain controller can adjust the gain coefficient k (k<1) in real time according to 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 amplifier for playback. 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 (e.g., close to 0 meters), 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, the value of the gain coefficient k is not changed immediately, but rather gradually adjusted at a certain rate until the target gain is reached. This ensures the continuity and stability of sound quality.

[0140] The preset feedback suppression distance threshold determines whether or not feedback suppression should be performed. Feedback suppression can be achieved using any effective method, but apart from directly reducing the gain k to 0, other methods cannot achieve complete suppression. Therefore, when the distance is less than the preset gain suppression distance threshold, simply setting the gain k to 0 will achieve complete suppression. This is because setting k to 0 effectively disables the amplification function, so it must be implemented at a sufficiently close distance. Once the distance increases, normal amplification will automatically resume. This avoids feedback caused by excessively close proximity while maintaining the amplification effect at a normal distance.

[0141] This application achieves 100% suppression of feedback because, once the distance between the microphone and the amplifier is determined, the microphone gain can be adjusted accordingly. For example, even in extreme cases where the microphone is directly attached to the amplifier diaphragm, the microphone gain can be set to 0, resulting in no positive feedback and eliminating feedback, thus achieving complete feedback suppression. Furthermore, in traditional amplifier equipment, obtaining the precise distance between the microphone and amplifier requires an effective ranging method. This application, without adding extra equipment or requiring a deliberate ranging method, allows the microphone to calculate the distance between the two based on the sound emitted from the amplifier, and then dynamically adjusts the microphone gain based on this distance to suppress feedback.

[0142] Existing technology directly acquires the sound frequency bands that are perceptible to the human ear from the speaker for judgment, and does not add any extra signals to the sound emitted by the speaker, so there is no modulation processing of extra signals. This application modulates the pulse signal generated by the microphone and shifts it to a frequency band that is imperceptible to the human ear, while leaving the frequency bands that the human ear can hear unprocessed, so there is no distortion in the listening experience.

[0143] Furthermore, existing technologies determine the distance to a speaker based on the sound intensity captured by a microphone. However, sound intensity is affected by many external environmental factors. For example, the movement of sound-absorbing or sound-reflecting objects between the speaker and microphone can change the sound intensity captured by the microphone, leading to misjudgments that the distance between the speaker and microphone is changing. Moreover, the degree of sound attenuation varies depending on the environment in which the speaker and microphone are placed, making it impossible for existing technologies to accurately measure distance. This application uses pulse modulation, which involves intermittently emitting a very brief sound in a frequency band inaudible to the human ear. The time delay required for the sound to leave the speaker and reach the microphone is directly related to the distance and completely independent of the surrounding environment, thus allowing for accurate distance measurement.

[0144] The algorithm in this application has a complexity approximately equivalent to that of a frequency shifting algorithm, and does not require the use of a high-computation chip.

[0145] Figure 3 This is a functional block diagram of the whistling suppression device provided in the embodiments 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 may be stored in the memory of the loudspeaker and executed by at least one processor to perform (see details). Figure 1 (Description) The function of howling suppression.

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

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

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

[0150] The calculation module 303 is used to calculate the distance between the microphone and the loudspeaker based on the pulse demodulation signal.

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

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

[0153] This application also provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements all or part of the steps of the aforementioned howling suppression method.

[0154] See Figure 4 The diagram shown is a structural schematic of a loudspeaker device provided in an embodiment of this application. In a preferred embodiment of this application, the loudspeaker 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 loudspeaker shown does not constitute a limitation of the embodiments of this application. The loudspeaker 4 may also include more or fewer other hardware or software, or different component arrangements than shown.

[0156] In some embodiments, the loudspeaker 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, microprocessors, application-specific integrated circuits, programmable gate arrays, digital processors, and embedded devices. The loudspeaker device 4 may also include client devices, which include, but are not limited to, any electronic product that can interact with a client via a keyboard, mouse, remote control, touchpad, or voice control device, such as personal computers, tablet computers, smartphones, and digital cameras.

[0157] It should be noted that the amplification device 4 is merely an example. Other existing or future electronic products that are suitable for this application should also be included within the scope of protection of this application and are incorporated herein by reference.

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

[0159] In some embodiments, the at least one processor 402 is the control unit of the loudspeaker 4, connecting various components of the loudspeaker 4 via various interfaces and lines. It executes programs or modules stored in the memory 401 and calls data stored in the memory 401 to perform various functions and process data of the loudspeaker 4. For example, when the at least one processor 402 executes a computer program stored in the memory, it implements all or part of the steps of the feedback suppression method described in this application embodiment; or it implements all or part of the functions of the feedback suppression device. The at least one processor 402 may be composed of integrated circuits, such as a single-packaged integrated circuit or multiple integrated circuits with the same or different functions, including combinations 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 communication between the memory 401 and the at least one processor 402, etc. Although not shown, the loudspeaker device 4 may also include a power supply (e.g., a battery) to power the various components. Preferably, the power supply can be logically connected to the at least one processor 402 via a power management device, thereby enabling functions such as charging, discharging, and power consumption management. The power supply may also include one or more DC or AC power supplies, recharging devices, power fault detection circuits, power converters or inverters, power status indicators, and other arbitrary components. The loudspeaker device 4 may also include various sensors, Bluetooth modules, Wi-Fi modules, etc., which will not be described in detail here.

[0161] The integrated unit implemented as a software functional module described above can be stored in a computer-readable storage medium. This software functional module, stored in a storage medium, includes several instructions to cause a loudspeaker (which may be a personal computer, a loudspeaker, or a network device, etc.) or a processor to execute portions of the methods described in the various embodiments of this application.

[0162] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and other division methods may be used in actual implementation.

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

Claims

1. A howling suppression method characterized by, The method includes: The microphone receives a mixed signal of sound played from an amplifier, wherein the mixed signal includes: a pulse modulation signal obtained by modulating and shifting the pulse signal generated by the microphone to a target frequency band, and the normal pickup signal of the microphone; The mixed signal is demodulated according to the pulse modulation signal to obtain the pulse demodulated signal; Calculating the distance between the microphone and the loudspeaker based on the pulse demodulation signal includes: Determine the first moment when the microphone outputs a pulse signal to the loudspeaker; Determine the fixed delay inside the loudspeaker; The second moment for identifying the pulse peak in the pulse demodulated signal; The distance between the microphone and the loudspeaker is calculated based on the delay, the first moment, the second moment, and the speed of sound propagation. Dynamically adjusting the current gain of the microphone based on the distance to suppress feedback includes: Compare 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, the current gain of the microphone is adjusted according to the distance, and the gain is proportional to the distance; When the distance is less than or equal to the preset gain suppression distance threshold, the current gain of the microphone is adjusted to a preset first value to completely suppress feedback. Wherein, the preset howling suppression distance threshold is greater than the preset gain suppression distance threshold.

2. The howling suppressing method according to claim 1, characterized by, The step of demodulating the mixed signal based on the pulse modulation signal to obtain the pulse demodulated signal includes: The mixed signal is filtered, and the frequency band signal centered on the carrier frequency of the pulse modulation signal is extracted; The extracted frequency band signal is demodulated to obtain a pulse demodulated signal.

3. The howling suppressing method according to claim 1, characterized by, The method further includes: When the distance is greater than the preset feedback suppression distance threshold, the current gain of the microphone is adjusted to a preset second value to restore normal amplification function.

4. The howling suppressing method according to claim 1, characterized by, The method further includes: The normal pickup signal from the microphone is filtered to obtain a filtered signal; The pulse modulation signal and the filtered signal are combined.

5. The howling suppressing method according to claim 4, characterized by, The cutoff frequency for filtering the normal pickup signal of the microphone is lower than the carrier frequency of the pulse modulation signal.

6. A howling suppressing device, characterized by comprising: The device includes: A receiving module is used to receive 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 shifting it to a target frequency band, and a normal pickup signal of the microphone; The demodulation module is used to demodulate the mixed signal according to the pulse modulation signal to obtain a pulse demodulated signal; The calculation module is used to calculate the distance between the microphone and the loudspeaker based on the pulse demodulation signal, including: Determine the first moment when the microphone outputs a pulse signal to the loudspeaker; Determine the fixed delay inside the loudspeaker; The second moment for identifying the pulse peak in the pulse demodulated signal; The distance between the microphone and the loudspeaker is calculated based on the delay, the first moment, the second moment, and the speed of sound propagation. A suppression module, used to dynamically adjust the current gain of the microphone based on the distance to suppress feedback, includes: Compare 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, the current gain of the microphone is adjusted according to the distance, and the gain is proportional to the distance; When the distance is less than or equal to the preset gain suppression distance threshold, the current gain of the microphone is adjusted to a preset first value to completely suppress feedback. Wherein, the preset howling suppression distance threshold is greater than the preset gain suppression distance threshold.

7. A sound amplification device, characterized by, The loudspeaker includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the feedback suppression method as described in any one of claims 1 to 5.

8. A computer-readable storage medium storing a computer program, the computer program comprising instructions that, when executed by a computer, cause the computer to perform the method of any one of claims 1 to 7. When the computer program is executed by the processor, it implements the steps of the howling suppression method as described in any one of claims 1 to 5.

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