Audio equalization method and earphone
By adjusting the equalization filter parameters by calculating the energy ratio of the retrieval signal and the error signal, the problems of high computational load and high power consumption in the existing technology are solved, achieving more efficient audio equalization and improving the real-time performance and user experience of the headphones.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-31
- Publication Date
- 2026-04-07
AI Technical Summary
Existing adaptive audio equalization methods involve high computational cost and high power consumption when calculating filter parameters, making it difficult to meet real-time requirements, especially affecting the real-time performance of audio playback when the user's wearing conditions change.
By obtaining the signal energy ratio of the acquired signal and the error signal, comparing the actual energy ratio with the ideal energy ratio, the filter parameters of the equalization filter are adjusted, reducing iterative calculations and lowering computational complexity and power consumption.
It improves the computational efficiency and real-time performance of adaptive audio equalization, reduces hardware performance requirements, and enhances the user's listening experience.
Smart Images
Figure CN121815161A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of audio processing, and more specifically, provides an audio equalization method and headphones. Background Technology
[0002] Due to differences in ear canal structure, size, and wearing habits among different users, the default sound effects of headphones may not achieve the best listening experience. For example, when a user wears the headphones too loosely, there is greater low-frequency leakage; when a user wears them too tightly, low-frequency signals accumulate in the ear, resulting in excessive energy. Therefore, the audio signal played from headphones may not reproduce the original audio playback quality under different ear positions, thus affecting the user's listening experience.
[0003] To address this issue, headphones can perform adaptive equalization processing on the audio signal. By adjusting the filter parameters in the headphones, they can compensate for low-frequency leakage when the fit is too loose, or reduce excessive leakage when the fit is too tight, so as to provide different users with the best possible listening experience of the original sound.
[0004] Currently, adaptive audio equalization typically uses LMS (least mean squared) to calculate and adjust filter parameters. However, LMS-based adaptive audio equalization requires multiple iterative calculations of filter parameters, resulting in high computational load and power consumption. This necessitates high-performance hardware to meet certain real-time requirements. Furthermore, users may adjust their headphone wearing in real time, further increasing computational load and impacting the real-time performance of audio playback. Therefore, LMS-based adaptive audio equalization is insufficient for scenarios with high real-time requirements in current audio playback, necessitating further improvements in the efficiency of adaptive audio equalization. Summary of the Invention
[0005] In view of this, this application aims to provide an audio equalization method and headphones to reduce the computational load and power consumption when adaptive equalization calibrates audio, while meeting hardware and real-time requirements.
[0006] In a first aspect, embodiments of this application provide an audio equalization method applied to headphones, the headphones including an equalization filter, a speaker, and a feedback microphone; the speaker including a sampling microphone; the audio equalization method includes: acquiring a sampling signal collected by the sampling microphone and an error signal collected by the feedback microphone; calculating the ratio of signal energy between the sampling signal and the error signal to obtain an actual energy ratio; comparing the actual energy ratio with a preset ideal energy ratio to obtain a frequency response difference; and adjusting the filter parameters of the equalization filter based on the frequency response difference until a new actual energy ratio fits the ideal energy ratio.
[0007] In a second aspect, embodiments of this application provide an earphone, including: a processor, a memory, a speaker, and a feedback microphone; the speaker further includes a re-sampling microphone; the processor is connected to the memory, the speaker, the re-sampling microphone, and the feedback microphone respectively; the processor further includes an equalization filter, the processor stores a program, and the processor is used to call the program to perform the audio equalization method as described in any of the first aspects.
[0008] The audio equalization method provided in this application acquires a backsampled signal and an error signal and calculates the signal energy. The signal energy of the backsampled signal represents the volume of the sound played by the speaker, and the signal energy of the error signal represents the volume of the sound actually heard by the user. In an ideal state where the artificial ear is correctly worn with headphones, the ratio of the signal energy between the backsampled signal and the error signal should be a fixed value, i.e., the ideal energy ratio. If the actual energy ratio (actual energy ratio) differs from the ideal energy ratio, it indicates that sound leakage or accumulation occurs when the user wears the headphones. Based on this, the actual energy ratio can be compared with the ideal energy ratio to obtain the frequency response difference, thereby guiding the adjustment of the equalization filter using the ideal energy ratio. Compared to existing adaptive equalization methods that calculate the leakage / accumulation degree by estimating the secondary path, the method provided in this application uses the signal energy ratio to represent the leakage / accumulation degree, which can reduce computational complexity to some extent. Meanwhile, in this application, the LMS method is no longer used to iterate the filter. Instead, the adjustment of the equalization filter parameters is guided by the comparison result (i.e., frequency response difference) between the actual energy ratio and the preset ideal energy ratio. This eliminates the need for multiple iterations, effectively reducing the amount of computation and thus reducing power consumption. Under the same hardware conditions, this can improve computational efficiency, provide real-time performance, or reduce the requirements for hardware performance while maintaining the same real-time performance requirements. Attached Figure Description
[0009] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0010] Figure 1 This is a flowchart of an audio equalization method according to an embodiment of this application; Figure 2 This is a schematic diagram illustrating the effect of adjusting the maximum gain of the equalizer filter based on the playback volume. Figure 3This is a schematic diagram illustrating the execution of an audio equalization method provided in an embodiment of this application; Figure 4 This is a schematic diagram illustrating the effect of an audio equalization method provided in an embodiment of this application; Figure 5 This is a schematic diagram of the structure of an earphone provided in one embodiment of this application; Figure 6 This is a schematic diagram of an adaptive equalization module provided in an embodiment of this application.
[0011] Icons: Processor 510; Adaptive Equalization Module 511; Estimation Module 5111; Application Module 5112; Memory 520; Speaker 530; Feedback Microphone 540; Digital-to-Analog Converter 550; Analog-to-Digital Converter 560. Detailed Implementation
[0012] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.
[0013] First, this application provides an audio equalization method that can be applied to headphones, wherein the audio equalization method can be executed by the headphone's processor.
[0014] In embodiments of this application, the headphones further include at least a speaker and a feedback microphone (or feedback microphone). The speaker is used to play audio, and the feedback microphone is used to collect the sound in the cavity between the headphones and the user's ear canal to obtain a feedback signal (also called an error signal). In embodiments of this application, the speaker may also include a sampling microphone, which is used to collect the sound played by the speaker to obtain a sampling signal.
[0015] In embodiments of this application, the headphones may further include an equalization filter, which may be implemented as a software program. For example, the headphones may include an adaptive equalization module, and the equalization filter is configured within the adaptive equalization module.
[0016] In embodiments of this application, the headphones may also include other structures, such as memory, communication modules, etc., which are not limited herein. The headphones performing this audio equalization method include, but are not limited to, in-ear, semi-in-ear, over-ear, wired headphones, and other headphone devices.
[0017] Please see Figure 1 , Figure 1 This is a flowchart illustrating an audio equalization method provided in an embodiment of this application. The audio equalization method includes: S110, acquire the acquired signal from the acquisition microphone and the error signal from the feedback microphone.
[0018] S120 calculates the ratio of signal energy between the acquired signal and the error signal to obtain the actual energy ratio.
[0019] S130 compares the actual energy ratio with the preset ideal energy ratio to obtain the frequency response difference.
[0020] S140 adjusts the filter parameters of the equalization filter based on the frequency response difference until the new actual energy ratio fits the ideal energy ratio.
[0021] In the embodiments of this application, the back sampling signal is collected by a back sampling microphone, which collects the signal of the sound played by the speaker. Therefore, the back sampling signal is used to characterize the audio signal of the sound played by the speaker. Correspondingly, the signal energy of the back sampling signal can also be used to characterize the volume of the sound played by the speaker.
[0022] The feedback signal is the signal collected by the feedback microphone, which is used to collect the sound from the cavity formed between the ear canal of the headphone wearer and the headphone. The feedback signal can be used for feedback noise reduction. In adaptive equalization, the signal collected by the speaker feedback microphone is used as the reference signal, and the Sz (secondary path) between the error signal and the reference signal is calculated to determine the degree of sound leakage or accumulation, so as to adjust the equalization filter according to the degree of sound leakage or accumulation.
[0023] In the embodiments of this application, the feedback signal is also used for adaptive equalization; therefore, the feedback signal can also be called an error signal, and the feedback microphone can also be called an error microphone. The error signal is the sound inside the ear canal, which is also the sound actually heard by the headphone wearer. Accordingly, the signal energy of the error signal also represents the volume of the sound actually heard by the user.
[0024] In the embodiments of this application, the ratio of signal energy between the sampled signal and the error signal can be calculated to obtain the actual energy ratio value, which represents the ratio of the volume of the sound played by the speaker to the volume of the sound heard by the user.
[0025] For users to hear the optimal sound quality they expect, their ear canal structure needs to match the structure of the artificial ear used in the test, and the headphones need to be worn in the same way as the artificial ear. This state can be understood as an ideal state, in which the ratio of the volume of the sound played by the speaker to the volume of the sound heard by the user should be within a preset range. Therefore, in an ideal state, the ratio of the signal energy of the sampled signal to the error signal should be a fixed value or within a certain range.
[0026] However, due to differences in ear canal structure and wearing methods among different users, it is difficult to achieve an ideal state. Therefore, in the embodiments of this application, the sampled signal and the error signal can be collected to characterize the user's actual wearing state by calculating the actual energy ratio between the two. This allows for the determination of whether there is sound leakage or accumulation in the current wearing of the headphones compared to the ideal state. In other words, the ideal energy ratio under the ideal state can be obtained, and the actual energy ratio can be compared with the ideal energy ratio to determine the degree of sound leakage or accumulation and obtain the frequency response difference.
[0027] Correspondingly, in adaptive equalization, parameters such as quality factor Q and gain of the equalization filter are adjusted according to the degree of sound leakage or accumulation in order to compensate for or reduce the sound played by the headphones, so that the user can hear the sound effect under ideal conditions as much as possible.
[0028] Compared to LMS's adaptive equalization method, this embodiment uses the signal-to-energy ratio to characterize the degree of sound leakage or accumulation, and then adjusts the filter parameters according to the frequency response difference. There is no need to use LMS to iteratively calculate the filter parameters, which effectively reduces computational complexity and power consumption. Under the same hardware conditions, the relevant calculations for adaptive equalization can be performed faster, improving the real-time performance of the adjustment. Alternatively, under the same real-time requirements, the hardware requirements for the headphone processor can be effectively reduced.
[0029] Next, we will further elaborate on the audio equalization method provided in this application.
[0030] During signal acquisition, the acquired signals are signals corresponding to different frequency points. For example, the acquired signals include acquired sub-signals corresponding to different frequency points, and the error signals include error sub-signals corresponding to different frequency points. Therefore, in the embodiments of this application, different frequencies can also be calibrated separately based on different frequency points.
[0031] Based on this, in the embodiments of this application, the actual energy ratio includes the actual frequency point energy ratio corresponding to different frequency points. Accordingly, in the embodiments of this application, S120, calculating the ratio of signal energy between the acquired signal and the error signal to obtain the actual energy ratio may include: for each frequency point, calculating the actual frequency point energy ratio corresponding to that frequency point based on the signal energy of the acquired sub-signal corresponding to that frequency point and the signal energy of the error sub-signal corresponding to that frequency point.
[0032] The calculation of signal energy can refer to existing technologies. For example, the signal amplitude at various frequency points can be obtained, and the energy can be calculated using the signal amplitude. In some embodiments of this application, the amplitude-frequency curves of the sampled signal and the error signal can also be obtained, and the signal energy of the sampled signal and the error signal at various frequency points can be calculated separately using their respective amplitude-frequency curves. The specific methods will not be described in detail again.
[0033] In some embodiments of this application, for each frequency point, calculating the actual frequency point energy ratio corresponding to that frequency point based on the signal energy of the corresponding back-collected sub-signal and the signal energy of the corresponding error sub-signal can include: calculating the signal energy corresponding to each back-collected sub-signal and the signal energy corresponding to each error sub-signal; performing energy smoothing on the signal energy of the back-collected sub-signals corresponding to multiple consecutive frequency points; performing energy smoothing on the signal energy of the error sub-signals corresponding to multiple consecutive frequency points; and for each frequency point, calculating the actual frequency point energy ratio corresponding to each frequency point based on the energy of the back-collected sub-signals and the signal energy of the corresponding error sub-signals after energy smoothing.
[0034] In this embodiment, energy smoothing can be performed on the sampled signal and the error signal respectively, using the energy variation amplitude between consecutive frequency points in the signal to avoid excessive changes in the filter parameters caused by excessive differences in signal energy between adjacent frequency points. This can effectively prevent abnormal sound playback from the headphones due to excessive differences in filter parameters, such as reducing pop noise. This method helps to improve the user's listening experience.
[0035] In some embodiments of this application, after obtaining the acquired signal and the error signal, the acquired signal and the error signal can be downsampled to reduce the number of sampling points, thereby further reducing computational efficiency.
[0036] Signal energy calculation is performed in the frequency domain. Therefore, after downsampling, the sampled signal and error signal can be Fourier transformed to convert them to the frequency domain for energy calculation.
[0037] In actual calculations, ideally, the frequency-to-energy ratio should be 1 or a reference value. However, in real-world scenarios, because a ratio is calculated, if the sampled sub-signal is too large and the error sub-signal is too small, the actual frequency-to-energy ratio will be too large. Conversely, if the sampled sub-signal is too small and the error sub-signal is too large, the actual frequency-to-energy ratio will be too small, even close to 0. Based on this, the energy ratio may exceed the recordable range, leading to errors or data loss. In such cases, adaptive equalization may not be performed correctly.
[0038] Therefore, in some embodiments of this application, the frequency point energy ratio can be converted into a difference calculation, and the difference can be used to characterize the frequency point energy ratio.
[0039] For example, in one embodiment, for each frequency point, calculating the ratio of the actual frequency point energy corresponding to the frequency point based on the signal energy of the sampled sub-signal corresponding to the frequency point and the signal energy of the error sub-signal corresponding to the frequency point may include: for each frequency point, calculating a first energy; calculating the difference between the signal energy of the error sub-signal corresponding to the frequency point and the first energy to obtain the ratio of the actual frequency point energy corresponding to the frequency point.
[0040] The secondary path and the desired path characterize the transfer function in different directions within an audio system. The secondary path is from the feedback microphone to the speaker, while the desired path is from the speaker to the feedback microphone. The specific value of the desired path can be measured during the research and development or laboratory phases, for example, using an artificial ear in an anechoic chamber setting. For details regarding the desired path, please refer to existing technologies; further details will not be elaborated upon here.
[0041] In this embodiment, the first energy is the product of the desired path from the speaker to the feedback microphone and the signal energy of the sampled sub-signal corresponding to that frequency point. For example, this calculation method is expressed as:
[0042] in, This represents the ratio of actual frequency energy. The signal energy represents the error sub-signal. This represents the signal energy of the sampled sub-signal. Indicates the desired path, It represents the primary energy.
[0043] By using the difference between the signal energy of the error sub-signal and the first energy to represent the actual frequency point energy ratio, the difference between the signal energy of the error sub-signal and the signal energy of the back-sampled sub-signal can be too large to obtain an accurate value, thus avoiding data loss and inaccuracy. This improves the accuracy and reliability of adaptive equalization using the method provided in the embodiments of this application.
[0044] Accordingly, the ideal energy ratio also includes the ideal frequency energy ratio corresponding to different frequency points. In some embodiments of this application, the ideal energy ratio is obtained in the following way: under a preset noise reduction test scenario, the test error signal and the test retrieval signal of the test headphones are acquired; an ideal amplitude-frequency curve is calculated based on the test error signal and the test retrieval signal; and the frequency energy ratio corresponding to each frequency point is calculated based on the ideal amplitude-frequency curve to obtain the ideal energy ratio.
[0045] The audio equalization method provided in this application can be applied to all headphone products. Each headphone can be configured with an ideal energy ratio, which is measured during the research and development and laboratory stages. Therefore, the ideal energy ratio configured for each headphone is preset. During the research and development and laboratory stages, the ideal energy ratio is obtained by testing with test headphones and an artificial ear. Therefore, in the embodiments of this application, when obtaining the ideal ratio, test headphones can be used, and the test headphones can be worn on the artificial ear for corresponding testing.
[0046] In this embodiment, the test can be conducted in a preset noise reduction test scenario, such as in a quiet environment in an anechoic chamber, to reduce environmental interference.
[0047] In the embodiments of this application, for ease of distinction, the signals acquired when obtaining the ideal energy ratio are referred to as the test error signal and the test retrieval signal. The signal energy of each signal can be calculated by calculating the amplitude-frequency curves of the test error signal and the test retrieval signal. The ideal amplitude-frequency curve includes the amplitude-frequency curve corresponding to the test error signal and the amplitude-frequency curve corresponding to the test retrieval signal.
[0048] Accordingly, the test error signal and the test retrieval signal also include sub-signals corresponding to different frequency points. After obtaining the ideal amplitude-frequency curve, the frequency point energy ratio corresponding to each frequency point is calculated based on the amplitude-frequency curve corresponding to the test error signal and the amplitude-frequency curve corresponding to the test retrieval signal in the ideal amplitude-frequency curve, respectively, to obtain an ideal energy ratio including the ideal frequency point energy ratios corresponding to multiple frequency points. The calculation method for the ideal frequency point energy ratio and the actual frequency point energy ratio is the same to avoid calculation errors caused by differences in calculation methods.
[0049] In some embodiments of this application, after obtaining the ideal amplitude-frequency curve through testing, the low frequencies can be enhanced to achieve better playback performance in the low-frequency band.
[0050] When determining the frequency response difference, the frequency difference at each frequency point can also be calculated separately to adjust the filter parameters corresponding to each frequency point. Therefore, in the embodiments of this application, S130, comparing the actual energy ratio with the preset ideal energy ratio, can include: for each frequency point, comparing the actual frequency energy ratio corresponding to that frequency point with the ideal frequency energy ratio corresponding to that frequency point to obtain the frequency response difference corresponding to that frequency point.
[0051] In the embodiments of this application, the comparison can be performed by calculating the difference between the two, and the leakage or accumulation can be indicated by the sign and magnitude of the frequency response difference. For example, the frequency response difference is the ratio of the actual frequency energy to the ideal frequency energy. When the frequency response difference is positive, it indicates that the actual frequency energy ratio is larger, which in turn indicates that the signal energy of the sampled sub-signal is too high and / or the signal energy of the error sub-signal is too low, i.e., leakage exists. Conversely, if the frequency response difference is negative, it indicates that the actual frequency energy ratio is smaller, which in turn indicates that the signal energy of the sampled sub-signal is too low and / or the signal energy of the error sub-signal is too high, i.e., accumulation exists.
[0052] In some other embodiments of this application, a further ratio between the actual energy ratio and the preset ideal energy ratio can be calculated to characterize the frequency response difference. When adjusting filter parameters, the frequency response difference ratio can be used to adjust them proportionally.
[0053] And S140, adjusting the filter parameters of the equalization filter based on the frequency response difference may also include: adjusting the filter parameters corresponding to each frequency point in the equalization filter based on the frequency response difference of each frequency point until the actual energy ratio of the new frequency point corresponding to each frequency point fits the ideal energy ratio of the frequency point.
[0054] In the embodiments of this application, fitting refers to the actual frequency energy ratio being the same as the ideal frequency energy ratio or having an error within a preset range. In headphones, audio needs to be processed by an equalization filter before output, such as amplifying or reducing the audio. Therefore, by adjusting the filter parameters of the equalization filter, the volume of the audio played by the speaker can be changed, thereby changing the signal energy of the new sampled signal and the error signal. Therefore, when the new actual frequency energy ratio is fitted to the ideal frequency energy ratio, the audio played by the headphones can more closely approximate the ideal playback effect.
[0055] Accordingly, in an equalization filter, different frequency points correspond to different filter parameters. For example, an equalization filter includes filters with different frequency ranges to process audio from different frequency bands. Therefore, the filter parameters corresponding to each frequency point in the equalization filter can be adjusted based on the differences in frequency response, so that the actual energy ratio of the new frequency point fits the ideal energy ratio of the frequency point.
[0056] In some embodiments of this application, the equalization filter includes multiple IIR filters connected in series, with the center frequencies of different IIR filters corresponding to different frequencies. The IIR filters can be software programs.
[0057] In the embodiments of this application, the IIR filter includes, but is not limited to, peak filters, notch filters, highshelf filters, and lowshelf filters. Different filters have different characteristics for different frequency bands. For example, peak filters are used to boost gain at specific frequency points to compensate for sensitive mid-to-high frequency ranges. Notch filters are used to suppress narrowband noise or formants to avoid ear canal resonance interference. Highshelf filters are used to uniformly adjust the overall gain in the mid-to-high frequency range to match the equal loudness curve of the human ear. Lowshelf filters focus on optimizing the low-frequency response and solving the problem of low-frequency attenuation at low volumes. They can be selected individually or used in combination according to actual needs.
[0058] In the embodiments of this application, the filter parameters of the IIR filter include a center frequency, which matches the frequency of the sampled sub-signal and the error sub-signal; that is, each frequency has a corresponding IIR filter. Accordingly, for each frequency, after determining the frequency response difference of that frequency, the IIR filter at the same frequency can be adjusted based on that frequency response difference.
[0059] In the embodiments of this application, the adjusted filter parameters may be gain, quality factor, or other parameters that affect audio output, and are not limited herein.
[0060] Taking gain adjustment as an example, in some embodiments of this application, adjusting the filter parameters corresponding to each frequency point in the equalization filter based on the frequency response difference of each frequency point may include: for each frequency point, adjusting the gain of the IIR filter corresponding to that frequency point based on the frequency response difference of that frequency point.
[0061] As mentioned earlier, if the signal energy difference between adjacent frequency points is too large, some abnormal sounds may occur. Correspondingly, if the signal energy of the audio corresponding to the same frequency point changes too much before and after adjustment, abnormalities may also occur. Therefore, in the embodiments of this application, adjustments can be made once or multiple times based on a preset step size until the new actual energy ratio fits the ideal energy ratio.
[0062] In the embodiments of this application, for each frequency point, adjusting the gain of the IIR filter corresponding to that frequency point based on the frequency response difference can include: determining whether the actual frequency point energy ratio is greater than the ideal frequency point energy ratio based on the frequency response difference; when it is determined that the actual frequency point energy ratio is less than the ideal frequency point energy ratio, increasing the gain of the IIR filter corresponding to that frequency point by a preset step size; and when it is determined that the actual frequency point energy ratio is greater than the ideal frequency point energy ratio, decreasing the gain of the IIR filter corresponding to that frequency point by a preset step size.
[0063] For example, when the frequency response difference is the difference between the actual frequency energy ratio and the ideal frequency energy ratio, if the frequency response difference is positive, it indicates that the actual frequency energy ratio is greater than the ideal frequency energy ratio, and the gain can be reduced by a preset step size. Conversely, if the frequency response difference is negative, it indicates that the actual frequency energy ratio is less than the ideal frequency energy ratio, and the gain can be increased by a preset step size.
[0064] In the embodiments of this application, the filter gain is adjusted by a preset step size to introduce a limit on the rate of change of the filter gain, thereby avoiding the abruptness of the hearing caused by sudden changes in gain.
[0065] Based on the acoustic characteristics of headphones and the frequency response model of the human ear canal, the sealing of the cavity formed by the headphones and the ear canal has a significant attenuation effect on the frequency response in the low frequency band, and individual wearing differences have the greatest impact on the low frequency, especially the frequency band below 1000Hz. Therefore, in the embodiments of this application, the low frequency band can also be appropriately enhanced, and the low frequency band filter can be focused to solve the core deviation in order to improve the subjective listening experience.
[0066] Therefore, in the embodiments of this application, the equalization filter includes an IIR filter with a center frequency of a preset low frequency point, where the preset low frequency point is the threshold point at which the human ear can hear low-frequency sounds. Accordingly, the frequency response difference corresponding to each preset low frequency point can be calculated, and the filter parameters of the filter corresponding to the preset low frequency point can be adjusted and optimized to the final result.
[0067] The preset low-frequency point can be determined based on the acoustic characteristics of the headphones and the frequency response model of the human ear canal. For example, the preset low-frequency point includes at least one of 62.5Hz, 125Hz, 250Hz, 500Hz, and 1000Hz. For details, please refer to existing headphone acoustic characteristics and human ear canal frequency response models, which will not be elaborated here.
[0068] As mentioned above, different types of IIR filters have different characteristics and different processing effects on different frequency bands. Peak filters and lowshelf filters are better at processing low frequency bands. Therefore, in the embodiments of this application, the IIR filters corresponding to each preset low frequency point can preferentially be lowshelf filters or peak filters.
[0069] Furthermore, in the embodiments of this application, the quality factor Q value of the IIR filter corresponding to each preset low frequency point can be taken as 0.5-1.5 to achieve wideband compensation, thereby achieving accurate frequency point calibration.
[0070] Self-equalization is used to calibrate audio, enabling headphones to achieve better playback performance. Therefore, in the embodiments of this application, after adjusting the filter parameters of the equalization filter based on frequency response differences, the audio to be played can be obtained; the audio to be played is then input into the equalization filter for filtering, so that the filtered audio to be played can be played.
[0071] There is a physical limit to the low-frequency output power of headphone speakers. Excessive boosting of low-frequency gain at high volumes can easily lead to distortion. It is necessary to avoid performance overload through targeted limitation. Therefore, in some embodiments of this application, after filtering the audio input equalization filter, at least one of the filtered audio input limiter and the cross-band dynamic range control module can be played later.
[0072] The principles and implementation methods of the limiter and the frequency band dynamic range control module can refer to existing technologies. In the embodiments of this application, the limiter is used to limit the signal energy of the output audio signal of the limiter in the time domain to a first preset dynamic range; the frequency band dynamic range control module is used to limit the output audio of the frequency band dynamic range control module in the frequency domain to a second preset dynamic range.
[0073] In the embodiments of this application, because the aforementioned embodiments focused on adjusting the low-frequency points, the compensation for the low frequencies was too large. After passing through the limiter, the signal energy of the high-frequency bands was also suppressed as a whole. Therefore, it is necessary to adjust different frequency bands in the low and high frequencies separately by frequency band dynamic range control to achieve better playback effect. The specific adjustment method can be configured according to the needs and will not be elaborated here.
[0074] The first preset dynamic range and the second dynamic range can be determined based on the upper limit of the speaker's output power, or they can be determined based on the dynamic range requirements of the digital-to-analog converter and analog-to-digital converter in the headphones, so as to avoid exceeding the dynamic range supported by the digital-to-analog converter and analog-to-digital converter.
[0075] In some embodiments of this application, before filtering the audio input to be played into the equalizer filter, the method may further include: acquiring the playback volume of the headphones; adjusting the maximum gain of the equalizer filter based on the playback volume until the signal energy of the output audio signal of the equalizer filter is within a third preset dynamic range. The headphone volume can be directly acquired through the upper-layer application.
[0076] In this embodiment, the maximum gain of the equalization filter can be limited for different playback volumes to avoid excessive sound affecting the user's listening comfort and meet loudness requirements, thus balancing sound quality stability and auditory comfort.
[0077] In other embodiments of this application, different desired paths can be set for different volume levels to use different desired paths for calculation when calculating the energy ratio, thereby achieving different fits.
[0078] For example, please refer to Figure 2 , Figure 2 This is a schematic diagram illustrating the effect of adjusting the maximum gain of the equalizer filter based on the playback volume. (Example) Figure 2 As shown, the curve with significant fluctuations is the frequency response curve without adaptive equalization. Under different test scenarios, the volume of the low-volume and low-frequency bands varies too much, resulting in poor sound quality stability and listening comfort. Therefore, adaptive equalization is needed for compensation. After adaptive equalization compensation, the volume of the low-frequency band is significantly improved, and the fluctuation of the frequency response curve is smaller. Consistent or minimally different sound playback effects can be obtained under different test conditions (corresponding to different curves). At the same time, as the volume increases, the maximum gain parameter of the low-frequency compensation of the adaptive equalization needs to be reduced to avoid dynamic range saturation after compensation, and to avoid abnormal sound caused by using limiters or cross-band dynamic range control modules for adjustment.
[0079] For ease of understanding, an example is provided here to illustrate the audio equalization method provided in this application. Please refer to [link / reference]. Figure 3 , Figure 3 This is a schematic diagram illustrating the execution of an audio equalization method provided in an embodiment of this application.
[0080] First, the error signal is obtained from the feedback microphone, and the back-sampled signal is obtained from the speaker through the back-sampled microphone. The error signal and the back-sampled signal are downsampled and Fourier transformed. Then, the energy of the sub-signals corresponding to each frequency point in the error signal and the back-sampled signal are calculated and smoothed.
[0081] The actual frequency energy ratio corresponding to each frequency point is calculated using the method mentioned above. The actual frequency energy ratio is then compared with the ideal frequency energy ratio to obtain the frequency response difference corresponding to each frequency point.
[0082] Then, based on the frequency response differences at each frequency point, the IIR filters corresponding to each frequency point are adjusted to obtain the adjusted equalization filters. The gain of the equalization filters can also be adjusted based on the volume.
[0083] Finally, the audio to be played passes through an equalizer filter, then is limited by a limiter, and the energy of the audio to be played is adjusted by a DRC (Dynamic Range Control) module before being output.
[0084] Please see Figure 4 , Figure 4 This is a schematic diagram illustrating the effect of an audio equalization method provided in an embodiment of this application. Figure 4As shown, the dashed lines represent sound leakage, with different dashed lines indicating leakage under different sound leakage test conditions, thus representing the sound leakage situation after being processed by the method provided in this application. Figure 4 It is evident that low-frequency sound leakage is quite noticeable in the 0-1000Hz range. However, after adaptive equalization processing using the method provided in this application, the leakage sound is significantly reduced. Under different sound leakage test conditions, the leakage remains largely consistent, and the collected frequency response is essentially the same.
[0085] In the embodiments of this application, the above-mentioned audio equalization method estimates the degree of low-frequency leakage or excessiveness of the in-ear playback signal by comparing the difference between the signal energy ratio between the speaker and the feedback microphone and the ideal energy ratio in real time. By adjusting the parameters of the IIR filter, the original audio data to be played is processed, thereby compensating for low-frequency leakage when the ear is too loose or reducing excessive leakage when the ear is too tight, in order to obtain the same listening experience as when the artificial ear is worn normally.
[0086] Furthermore, in the embodiments of this application, the sound effects can be adjusted based on the above, and the bass can be enhanced to provide users with a better playback experience.
[0087] Based on the same inventive concept, this application also provides an earphone, which includes, but is not limited to, in-ear, semi-in-ear, over-ear, and wired earphones.
[0088] Please see Figure 5 , Figure 5 This is a schematic diagram of an earphone provided according to an embodiment of this application. In this embodiment, the earphone includes: a processor 510, a memory 520, a speaker 530, and a feedback microphone 540.
[0089] In the embodiments of this application, the speaker 530 also includes a sampling microphone, which is not shown in the figures, but its specific structure can be found in existing speakers.
[0090] In the embodiments of this application, the processor 510 is connected to the memory 520, the speaker 530, the sampling microphone, and the feedback microphone 540, respectively.
[0091] In embodiments of this application, the processor may include an adaptive equalization module 511, which includes an equalization filter.
[0092] In embodiments of this application, the headphones may further include an analog-to-digital converter (ADC) 560, a digital-to-analog converter (DAC) 550, a communication module, and other structures, without limitation. The ADC 560 and DAC 550 can be software or hardware. If the ADC 560 and DAC 550 are hardware, they are software modules within the processor. If they are hardware, the ADC 560 is connected between the feedback microphone and the processor, and the DAC 550 is connected between the speaker and the processor.
[0093] In embodiments of this application, the processor 510 may further include software program modules such as a limiter and a segmented dynamic range control module.
[0094] In the embodiments of this application, the memory stores a program, and the processor 510 can call the program stored in the memory 520 to execute the aforementioned audio equalization method. The specific content of the audio equalization method can be referred to the previous text, and will not be elaborated here.
[0095] In the embodiments of this application, the acquisition of signals, calculation of energy ratios and adjustment of equalization filters in the above-described audio equalization method can be performed by the adaptive equalization module 511.
[0096] like Figure 6 As shown, Figure 6 This is a schematic diagram of an adaptive equalization module provided in an embodiment of this application. In this embodiment, the adaptive equalization module 511 may include an estimation module 5111 and an application module 5112. The estimation module 5111 is used to acquire error signals and retrieval signals, and calculate frequency response differences. The equalization filter is configured in the application module 5112, and the estimation module 5111 can adjust the equalization filter in the application module 5112 based on the frequency response differences.
[0097] Based on the same inventive concept, embodiments of this application also provide a readable storage medium storing a program that can be executed by a processor to perform the audio equalization method provided in the foregoing embodiments. The processor may be a headphone processor.
[0098] In the embodiments provided in this application, it should be understood that the disclosed methods and devices can also be implemented in other ways. The device embodiments described above are merely illustrative. The functional modules in the various embodiments of this application can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.
[0099] The above embodiments can be freely combined without conflict, and the resulting embodiments are covered within the protection scope of this application.
[0100] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
[0101] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
Claims
1. An audio equalization method, characterized in that, Applied to headphones, the headphones include an equalization filter, a speaker, and a feedback microphone; the speaker includes a sampling microphone. The audio equalization method includes: The acquired signal collected by the acquisition microphone and the error signal collected by the feedback microphone are obtained; Calculate the ratio of signal energy between the acquired signal and the error signal to obtain the actual energy ratio value; The frequency response difference is obtained by comparing the actual energy ratio with the preset ideal energy ratio. The filter parameters of the equalization filter are adjusted based on the frequency response difference until the new actual energy ratio fits the ideal energy ratio.
2. The audio equalization method according to claim 1, characterized in that, The acquired signal includes acquired sub-signals corresponding to different frequency points; the error signal includes error sub-signals corresponding to different frequency points. The actual energy ratio includes the actual frequency energy ratio corresponding to different frequency points; The calculation of the signal energy ratio between the acquired signal and the error signal to obtain the actual energy ratio value includes: For each frequency point, the actual frequency point energy ratio corresponding to that frequency point is calculated based on the signal energy of the sampled sub-signal corresponding to that frequency point and the signal energy of the error sub-signal corresponding to that frequency point. The step of comparing the actual energy ratio with the preset ideal energy ratio includes: For each frequency point, the actual frequency energy ratio corresponding to that frequency point is compared with the ideal frequency energy ratio corresponding to that frequency point to obtain the frequency response difference corresponding to that frequency point. The adjustment of the filter parameters of the equalization filter based on the frequency response difference includes: Based on the frequency response differences of each frequency point, the filter parameters corresponding to each frequency point in the equalization filter are adjusted until the actual energy ratio of the new frequency point corresponding to each frequency point fits the ideal energy ratio of the frequency point.
3. The audio equalization method according to claim 2, characterized in that, For each frequency point, the calculation of the actual frequency point energy ratio based on the signal energy of the corresponding sampled sub-signal and the signal energy of the corresponding error sub-signal includes: Calculate the signal energy corresponding to each of the acquired sub-signals and the signal energy corresponding to each of the error sub-signals; Energy smoothing is performed on the signal energy of the sub-signals corresponding to multiple consecutive frequency points; Energy smoothing is performed on the signal energy of error sub-signals corresponding to multiple consecutive frequency points; For each frequency point, the actual frequency point energy ratio corresponding to each frequency point is calculated based on the signal energy of the corresponding sampled sub-signal and the signal energy of the corresponding error sub-signal after energy smoothing.
4. The audio equalization method according to claim 2, characterized in that, For each frequency point, the calculation of the actual frequency point energy ratio based on the signal energy of the corresponding sampled sub-signal and the signal energy of the corresponding error sub-signal includes: For each frequency point, a first energy is calculated; the first energy is the product of the expected path from the loudspeaker to the feedback microphone and the signal energy of the sampled sub-signal corresponding to that frequency point. Calculate the difference between the signal energy of the error sub-signal corresponding to the frequency point and the first energy to obtain the actual frequency point energy ratio corresponding to the frequency point.
5. The method according to claim 2, characterized in that, The ideal energy ratio is obtained through the following method: Under a preset noise reduction test scenario, the test error signal and test feedback signal of the test earphone are acquired; the test earphone is worn on an artificial ear; Calculate the ideal amplitude-frequency curve based on the test error signal and the test retrieval signal; Based on the ideal amplitude-frequency curve, the frequency point energy ratio corresponding to each frequency point is calculated to obtain the ideal energy ratio.
6. The audio equalization method according to claim 2, characterized in that, The equalization filter includes multiple IIR filters, and the center frequency of each IIR filter corresponds to a different frequency. The adjustment of the filter parameters corresponding to each frequency point in the equalization filter based on the frequency response differences of each frequency point includes: For each frequency point, the gain of the corresponding IIR filter is adjusted based on the frequency response difference of that frequency point.
7. The audio equalization method according to claim 6, characterized in that, The adjustment of the gain of the IIR filter corresponding to the frequency point based on the frequency response difference of the corresponding frequency point includes: Based on the frequency response difference, determine whether the actual frequency energy ratio is greater than the ideal frequency energy ratio; When the actual frequency energy ratio is determined to be less than the ideal frequency energy ratio, the gain of the IIR filter corresponding to that frequency is increased by a preset step size. When the actual frequency energy ratio is determined to be greater than the ideal frequency energy ratio, the gain of the IIR filter corresponding to that frequency is reduced by the preset step size.
8. The audio equalization method according to claim 7, characterized in that, The equalization filter includes an IIR filter with a center frequency of a preset low frequency point, where the preset low frequency point is the threshold point at which the human ear can hear low-frequency sounds.
9. The audio equalization method according to claim 8, characterized in that, The preset low-frequency point includes at least one of 62.5Hz, 125Hz, 250Hz, 500Hz, and 1000Hz.
10. The audio equalization method according to claim 8, characterized in that, The IIR filters corresponding to each preset low-frequency point are either lowshelf filters or peak filters.
11. The audio equalization method according to any one of claims 1-10, characterized in that, After adjusting the filter parameters of the equalization filter based on the frequency response difference, the method further includes: Get the audio to be played; The audio to be played is input into the equalization filter for filtering; The filtered audio to be played is input to at least one of a limiter and a frequency band dynamic range control module before playback; the limiter is used to limit the signal energy of the output audio signal of the limiter in the time domain within a first preset dynamic range; the frequency band dynamic range control module is used to limit the output audio of the frequency band dynamic range control module in the frequency domain within a second preset dynamic range.
12. The audio equalization method according to claim 11, characterized in that, Before inputting the audio to be played into the equalizer filter for filtering, the method further includes: Get the playback volume of the headphones; The maximum gain of the equalizer is adjusted based on the playback volume until the signal energy of the output audio signal of the equalizer is within a third preset dynamic range.
13. An earphone, characterized in that, include: Processor, memory, speaker, feedback microphone; the speaker also includes a sampling microphone; The processor is connected to the memory, the speaker, the acquisition microphone, and the feedback microphone, respectively. The processor further includes an equalization filter, and the processor stores a program for invoking the program to perform the audio equalization method as described in any one of claims 1-12.