A method for modeling audio data in 3D space as a colored balloon model

Abstract

This invention relates to the field of audio and video signal processing and visualization technology, specifically to a method for modeling audio data in 3D space as a colored balloon model: Compared with traditional index testing, this method combines data processing and 3D visualization, which can more intuitively evaluate the performance of loudspeakers in space, especially their directivity, and can simply and clearly present the performance capabilities of loudspeaker systems in various directions. At the same time, this method can be combined with traditional index testing methods to evaluate the performance of loudspeaker systems from different perspectives.

Description

Technical Field

[0001] The present invention relates to the technical field of audio and video signal processing and visualization, and in particular to a method for modeling audio data in a 3D space as a color balloon model. Background Art

[0002] In today's society, with the continuous development of science and technology and the improvement of living standards, people's pursuit of sound quality is also increasing. Many fields such as home entertainment systems, virtual reality experiences, mobile communication devices, car interior audio systems, and professional audio equipment all have extremely high requirements for sound quality. Speakers, as an indispensable sound source component in these devices, their performance directly affects the sound quality of the entire audio and video system. Therefore, strict evaluation of speaker performance is not only of great guiding significance for consumers to choose products, but also promotes the technological progress and quality improvement of audio equipment. In addition, through accurate speaker evaluation, manufacturers can better understand how various designs and materials affect sound quality, and then make more reasonable adjustments and optimizations during the research and development process.

[0003] However, traditional speaker sound quality evaluation methods, such as hum detection, total harmonic distortion plus noise, pitch ratio, prominence ratio, and signal-to-noise ratio, are all implemented by measuring a single indicator of a specific audio signal. In practical applications, these methods usually focus on evaluating the sound source response of a single point, and cannot provide comprehensive and intuitive information about the distribution of the entire spatial sound field. Summary of the invention

[0004] The purpose of the present invention is to provide a method for modeling audio data in a 3D space as a colored balloon model, so as to solve the problem that traditional speaker sound quality evaluation methods usually focus on evaluating the sound source response of a single point and cannot provide comprehensive and intuitive information about the distribution of the entire spatial sound field.

[0005] To achieve the above object, the present invention provides a method for modeling audio data in a 3D space as a colored balloon model. The method for modeling audio data in a 3D space as a colored balloon model comprises the following steps:

[0006] S0, measure the maximum linear unit of the single speaker;

[0007] S1. Determine the far field of the loudspeaker according to the far field definition criteria;

[0008] S2, placing the microphone test group within the far field range and arranging them according to the angular resolution;

[0009] S3. In a free field environment, a pulse signal is played with a loudspeaker and the pulse signal is picked up with a microphone;

[0010] S4, setting the sampling rate according to Shannon's theorem, and resampling the picked-up audio signal according to the sampling rate;

[0011] S5. To prevent spectrum leakage, select a time window function according to actual test requirements;

[0012] S6, converting the time domain signal into a frequency domain signal by Fourier transform;

[0013] S7, dynamically expand frequency domain data according to free field conditions and required measurement radius;

[0014] S8, setting the amplitude of the frequency band less than 20 Hz and greater than 20 kHz in the frequency domain to 0;

[0015] S9. According to the R80 priority number rule, accurately calculate the required octave frequency array;

[0016] S10, calculating the sound pressure at each measurement point at a specific octave frequency using bilinear interpolation or inverse distance weighted interpolation;

[0017] S11, calculating the sound pressure level of each data point obtained in the previous step based on the reference sound pressure;

[0018] S12, generating an angle array of direction angle and elevation angle according to the frequency resolution of the mesh data collection;

[0019] S13, using a three-dimensional drawing system to bind the mesh surface sound pressure level data with the angle array, and mapping the obtained data to a spherical coordinate system, and drawing a colored balloon model, wherein the mesh surface data represents the radius of each direction;

[0020] S14. Add air inhalation and deflation functions to the balloon model, so that the three-dimensional balloon supports dynamic presentation;

[0021] S15. Calculate the directional factor and directional gain according to the directional transfer function, and finally calculate the directivity parameter.

[0022] In step S5: the window function of the Hanning window is: Where ω(n) is the value of the window function at the nth point, N is the length of the window (i.e. the total number of points in the window), and n is the sequence number of the current point, from 0 to N-1.

[0023] In step S6: the function of continuous Fourier transform is: Where f(t) represents the continuous input signal, F(w) represents the continuous Fourier transform, ω is the continuous frequency, k is the discrete frequency index, and j is the imaginary unit.

[0024] In step S7: the formula for free field radius adjustment is: Among them, P(f,r2,φ,θ) represents the complex sound pressure at the distance r2, azimuth θ and elevation Φ. Similarly, P(f,r1,φ,θ) represents the complex sound pressure at the distance r1, azimuth θ and elevation Φ, where the wave number k = 2Πf / c.

[0025] In step S10: the inverse distance weighted interpolation formula is: Among them, V(x) is the predicted value of the point to be interpolated, V i is the value of the ith known point, d i is the distance between the i-th known point and the point to be interpolated, p is the weight index of the distance, usually 1 or 2. This parameter can adjust the sensitivity of the distance effect, and n is the total number of known points used for interpolation.

[0026] In step S11: the calculation formula of the sound pressure level is: Among them, L p represents the sound pressure level, p represents the sound pressure, p ref Represents the reference sound pressure, which is 20 microPa.

[0027] In step S15: the formula for calculating the direction factor is: Among them, Γ(f,θ,φ) represents the directivity factor, P(f,r,θ,φ) represents the complex sound pressure at any angle, and P(f,r,θ r ,φ r ) represents the complex sound pressure in the reference direction, that is, the axial complex sound pressure.

[0028] In step S15: the formula for calculating the directivity factor is: Where Q(f) represents the directivity factor and Γ(f,θ,φ) represents the directional factor.

[0029] In step S15: the formula for calculating the directional index is: DI(f) = 10log 10 Q(f), also known as directivity factor in dB.

[0030] The present invention provides a method for modeling audio data in a 3D space as a colored balloon model. Compared with traditional index tests, the method combines data processing and three-dimensional visualization solutions, which can more intuitively evaluate the performance of a speaker in space, especially its directivity, and can simply and clearly present the performance capabilities of the speaker system in various directions. At the same time, the method can be combined with traditional index test solutions to evaluate the performance of the speaker system from different angles. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 It is a specific flow chart of the method provided by the present invention for modeling audio data in a 3D space as a colored balloon model.

[0033] Figure 2 It is a pulse signal diagram in a specific embodiment of the present invention.

[0034] Figure 3 In the specific embodiment of the present invention, Figure 2 The three-dimensional balloon model obtained by playing the pulse signal.

[0035] Figure 4 In the specific embodiment of the present invention, Figure 2 After the played pulse signal is deflated, observe only the balloon model diagram on the front of the speaker system. DETAILED DESCRIPTION

[0036] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0037] See also Figures 1 to 4 The present invention provides a method for modeling audio data in a 3D space as a colored balloon model. The method for modeling audio data in a 3D space as a colored balloon model comprises the following steps:.

[0038] S0, measure the maximum linear unit of the single speaker (i.e. the longest side of the speaker), and record it as L;

[0039] S1. Calculate the far field critical radius R according to the far field definition rules far , and select the radius of data collection r = 1m according to this radius;

[0040] S2. Place the microphone in the far field, here choose r = 1m, and set the angular resolution to 5 degrees;

[0041] S3. In the free field environment guaranteed by the fully anechoic room, use the speaker to be tested to play the pulse signal, pick up the pulse signal through the microphone, and name the pulse signals in each direction according to certain rules;

[0042] S4. Set the sampling rate to fs = 48000 Hz, and resample the time domain signals of each direction just picked up according to this sampling rate. The resampled data should include the time array Times, the real part array Real of the sound pressure, and the imaginary part array Imag of the sound pressure;

[0043] S5. Add a Hanning window with an effective length of 7.6ms to all the above data files. The length of the window function should be enough to limit the time of the first reflection sound. In the part outside the window function, the frequency range of 20-20k should be filled with 0;

[0044] S6. Perform Fourier transform on the above-mentioned resampled and windowed time domain files to obtain frequency domain data at each angle. After this step, each frequency domain file should include the following three parts: frequency array Freqs, sound pressure amplitude array Magn, and phase array Phase;

[0045] S7. Since the radius to be measured selected here is consistent with the measured radius, we will not expand the data and keep the above data unchanged;

[0046] S8. Since the human hearing range is 20Hz-20KHz, to avoid unnecessary calculations, we delete the values ​​that are not in the audible range in the frequency domain data for each file. Note that the three arrays of frequency domain data need to be updated at the same time.

[0047] S9, first calculate the 1 / 24 octave array according to the R80 priority number, and then take a number every 8 to get the 1 / 3 octave array OctFreq, which will be used for subsequent interpolation and directivity calculation;

[0048] S10, performing IDW inverse distance weighted interpolation on the sound pressure amplitude array according to the octave array OctFreq and the frequency domain array Freqs;

[0049] S11, converting the interpolated array from sound pressure to sound pressure level, with a reference sound pressure of 20 μPa;

[0050] S12, according to the angular resolution of 5 degrees during data collection, generate an azimuth array Angle and an elevation array Phi, wherein the azimuth array size should be 355 / 5+1, covering 360 degrees, and the elevation array size should be 180 / 5, covering 180 degrees;

[0051] S13. After the above steps, we have obtained all the data for three-dimensional drawing, which are the interpolated sound pressure amplitude array and two angle arrays, so the task of this step is to match them one by one and map them to the spherical coordinate system;

[0052] S14, mapping the color value according to the radius size, and adding a step-by-step scaling function according to an appropriate scale factor, the specific method is to set a radius change amount and a scale factor, and multiply them, and when scaling, gradually accumulate or gradually decrease their product as the radius change amount in each direction, and sum the value outside the reference direction with the variable, and finally scale the value outside the reference direction to the original proportion;

[0053] S15. Calculate the directivity factor based on the sound pressure data obtained by interpolation without inflation or deflation, further calculate the directivity parameters, and finally calculate the directivity index based on the directivity parameters. The calculation results are: directivity factor 4.19, directivity index 6.22.

[0054] In this embodiment, compared with traditional indicator testing, this method combines data processing and three-dimensional visualization solutions, which can more intuitively evaluate the performance of the speaker in space, especially its directivity, and can simply and clearly present the performance capabilities of the speaker system in all directions. At the same time, this method can be combined with traditional indicator testing solutions to evaluate the performance of the speaker system from different angles.

[0055] The far field definition in step S1 is closely related to the longest line length L measured in step S0. far Need to meet condition 1: R far >>L; Condition 2: R far >>λ; Condition 3: Among them, condition one requires that the test distance is greater than the maximum geometric dimension, condition two requires that the distance is greater than the wavelength, and condition three is mainly applicable to large speaker systems (such as line arrays, sound bars and sound boards).

[0056] In step S3 , it is required to perform measurement in a free sound field, where the free sound field should use an anechoic room that meets corresponding standards.

[0057] The dynamic adjustment of frequency domain data in step S7 means that for the convenience of measurement, the original signal collected by the microphone may not be based on the target radius. At this time, according to the propagation law of sound in the free field, the data can be expanded within the free field radius according to the inverse law of sound pressure with distance.

[0058] The octave calculation in step S9 can be calculated using the octave definition formula, but here the calculation is combined with the definition of R80 and the octave, where the R80 priority number represents a part of the 1 / 24 octave. When generating the octave array, the octave array can be customized as needed, wherein 1 / 3 octave is preferably used.

[0059] Both algorithms for frequency domain interpolation in step S10 are optional.

[0060] In step S11, the reference sound pressure corresponds to the minimum sound pressure that the human ear can perceive at a frequency of 1000 Hz, which is 20 μPa (20×10 -6 Pa).

[0061] In step S12, the angular resolution may refer to 1 degree, 2.5 degrees, 5 degrees, 10 degrees or other suitable resolutions, wherein the preferred resolution is a common factor of 90, 180, and 360. In actual testing, the acceptable angle value is an integer, which is conducive to subsequent data processing based on computer programs.

[0062] In step S13, before drawing the colored balloon model, it is necessary to generate reference axes, x-axis, y-axis and z-axis according to the balloon data composition. When evaluating a certain direction, a reference direction can be obtained, that is, the axial direction of a speaker system is determined as a reference.

[0063] In step S13, a simplified line model of the speaker system is added to the three-dimensional visualization system to more intuitively present the position of each direction relative to the speaker system.

[0064] In step S14, in order to dynamically simulate the zoom function of the color balloon, it is necessary to dynamically adjust the dB range of the color mapping according to the demand, and at the same time, the coordinate radius with an adjusted radius less than 0 is normalized to 0 to achieve the expected visualization effect.

[0065] The directional transfer function and directivity gain in step S15 should be calculated according to the formula provided later.

[0066] The formula provided by this method is as follows:

[0067] In step S5: the window function of the Hanning window is: Where ω(n) is the value of the window function at the nth point, N is the length of the window (i.e. the total number of points in the window), and n is the sequence number of the current point, from 0 to N-1.

[0068] In step S6: the function of continuous Fourier transform is: Where f(t) represents the continuous input signal, F(w) represents the continuous Fourier transform, ω is the continuous frequency, k is the discrete frequency index, and j is the imaginary unit.

[0069] In step S7: the formula for free field radius adjustment is: Among them, P(f,r2,φ,θ) represents the complex sound pressure at the distance r2, azimuth θ and elevation Φ. Similarly, P(f,r1,φ,θ) represents the complex sound pressure at the distance r1, azimuth θ and elevation Φ, where the wave number k = 2Πf / c.

[0070] In step S10: the inverse distance weighted interpolation formula is: Among them, V(x) is the predicted value of the point to be interpolated, V i is the value of the ith known point, d i is the distance between the i-th known point and the point to be interpolated, p is the weight index of the distance, usually 1 or 2. This parameter can adjust the sensitivity of the distance effect, and n is the total number of known points used for interpolation.

[0071] In step S11: the calculation formula of the sound pressure level is: Among them, L p represents the sound pressure level, p represents the sound pressure, p ref Represents the reference sound pressure, which is 20 microPa.

[0072] In step S15: the formula for calculating the direction factor is: Among them, Γ(f,θ,φ) represents the directivity factor, P(f,r,θ,φ) represents the complex sound pressure at any angle, and P(f,r,θ r ,φ r ) represents the complex sound pressure in the reference direction, that is, the axial complex sound pressure.

[0073] In step S15: the formula for calculating the directivity factor is: Where Q(f) represents the directivity factor and Γ(f,θ,φ) represents the directional factor.

[0074] In step S15: the formula for calculating the directional index is: DI(f) = 10log 10 Q(f), also known as directivity factor in dB.

[0075] What is disclosed above is only a preferred embodiment of the present invention, and it certainly cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A method for modeling audio data in a 3D space as a colored balloon model, characterized in that: Here are the steps: S0, measure the maximum linear unit of the single speaker; S1. Determine the far field of the loudspeaker according to the far field definition criteria; S2, placing the microphone test group within the far field range and arranging them according to the angular resolution; S3. In a free field environment, a pulse signal is played with a loudspeaker and the pulse signal is picked up with a microphone; S4, setting the sampling rate according to Shannon's theorem, and resampling the picked-up audio signal according to the sampling rate; S5. To prevent spectrum leakage, select a time window function according to actual test requirements; S6, converting the time domain signal into a frequency domain signal by Fourier transform; S7, dynamically expand frequency domain data according to free field conditions and required measurement radius; S8, setting the amplitude of the frequency band less than 20 Hz and greater than 20 kHz in the frequency domain to 0; S9. According to the R80 priority number rule, accurately calculate the required octave frequency array; S10, calculating the sound pressure at each measurement point at a specific octave frequency using bilinear interpolation or inverse distance weighted interpolation; S11, calculating the sound pressure level of each data point obtained in the previous step based on the reference sound pressure; S12, generating an angle array of direction angle and elevation angle according to the frequency resolution of the mesh data collection; S13, using a three-dimensional drawing system to bind the mesh surface sound pressure level data with the angle array, and mapping the obtained data to a spherical coordinate system, and drawing a colored balloon model, wherein the mesh surface data represents the radius of each direction; S14. Add air inhalation and deflation functions to the balloon model, so that the three-dimensional balloon supports dynamic presentation; S15, calculating the directional factor and the directional gain according to the directional transfer function, and finally calculating the directivity parameter; In step S7, the dynamically expanded frequency domain data means that, for the convenience of measurement, the original signal collected by the microphone may not be based on the target radius. At this time, according to the propagation law of sound in the free field, the data can be expanded within the free field radius according to the inverse law of sound pressure with distance; In step S7: the formula for free field radius adjustment is: Among them, P(f,r2,φ,θ) represents the complex sound pressure at the distance r2, azimuth θ and elevation Φ. Similarly, P(f,r1,φ,θ) represents the complex sound pressure at the distance r1, azimuth θ and elevation Φ, where the wave number k = 2Πf / c.

2. The method for modeling audio data in a 3D space as a colored balloon model according to claim 1, characterized in that: In step S5: the window function of the Hanning window is: Where ω(n) is the value of the window function at the nth point, N is the length of the window, and n is the sequence number of the current point, from 0 to N-1.

3. The method for modeling audio data in a 3D space as a colored balloon model as claimed in claim 2, characterized in that: In step S6: the function of continuous Fourier transform is: Where f(t) represents the continuous input signal, F(w) represents the continuous Fourier transform, ω is the continuous frequency, k is the discrete frequency index, and j is the imaginary unit.

4. The method for modeling audio data in a 3D space as a colored balloon model according to claim 1, characterized in that: In step S10: the inverse distance weighted interpolation formula is: Among them, V(x) is the predicted value of the point to be interpolated, V i is the value of the ith known point, d i is the distance between the i-th known point and the point to be interpolated, p is the weight index of the distance, usually 1 or 2. This parameter can adjust the sensitivity of the distance effect, and n is the total number of known points used for interpolation.

5. The method for modeling audio data in a 3D space as a colored balloon model as claimed in claim 4, characterized in that: In step S11: the calculation formula of the sound pressure level is: Among them, L p represents the sound pressure level, p represents the sound pressure, p ref Represents the reference sound pressure, which is 20 microPa.

6. The method for modeling audio data in a 3D space as a colored balloon model as claimed in claim 5, characterized in that: In step S15: the formula for calculating the direction factor is: Among them, Γ(f,θ,φ) represents the directivity factor, P(f,r,θ,φ) represents the complex sound pressure at any angle, and P(f,r,θ r ,φ r ) represents the complex sound pressure in the reference direction, that is, the axial complex sound pressure.

7. The method for modeling audio data in a 3D space as a colored balloon model as claimed in claim 6, characterized in that: In step S15: the formula for calculating the directivity factor is: Where Q(f) represents the directivity factor and Γ(f,θ,φ) represents the direction factor.

8. The method for modeling audio data in a 3D space as a colored balloon model as claimed in claim 7, characterized in that: In step S15: the formula for calculating the directional index is: DI(f) = 10log 10 Q(f), also known as directivity factor in dB.

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