Semi-anechoic chamber measurement system for air conditioning noise testing

Abstract

This invention relates to the field of noise testing technology and discloses a semi-anechoic chamber measurement system for air conditioner noise testing, comprising: a conversion analysis unit, a co-calibration unit, an attenuation compensation unit, and a judgment unit. The conversion analysis unit obtains a reference conversion efficiency value through reference acoustic wave calibration, accurately capturing the correspondence between the initial sound pressure and capacitance. The thermally sensitive attenuation factor generated by the co-calibration unit comprehensively reflects the influence of temperature changes on the microphone diaphragm elastic modulus and electret charge attenuation, solving the problem of decreased conversion efficiency due to temperature rise. Meanwhile, the attenuation compensation unit obtains a dynamic capacitance response value sequence through inverse compensation, avoiding further attenuation of the amplitude of low-noise weak electrical signals. The judgment unit accurately determines the degree of elimination of temperature drift and electromagnetic coupling effects by analyzing electromagnetic coupling residual values ​​and mutual information redundancy, preventing the true sound pressure from being masked by interference signals and ensuring the accuracy of air conditioner noise test data.

Description

Technical Field

[0001] This invention relates to the field of noise testing technology, and more specifically to a semi-anechoic chamber measurement system for testing air conditioning noise. Background Technology

[0002] Currently, in the semi-anechoic chamber air conditioning noise test, electret microphones are used to collect air conditioning noise sound waves, convert the sound wave signals into weak electrical signals, and after the signals are amplified by a preamplifier, they are filtered and noise reduced before the relevant data of air conditioning noise are calculated. However, the above measurement method still has the following drawbacks in the noise test of air conditioners: when the ambient temperature in the semi-anechoic chamber rises due to the heat dissipation of the air conditioner, the change in the elastic modulus of the diaphragm of the electret condenser microphone and the attenuation of its charge will reduce the efficiency of converting sound pressure into capacitance change, further reducing the amplitude of the weak electrical signal corresponding to low noise. This weak signal is easily coupled with the electromagnetic noise radiated by the test equipment during transmission, reducing the signal-to-noise ratio and causing the sound pressure to be masked by the interference signal, thus affecting the test results of air conditioner noise. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a semi-anechoic chamber measurement system for air conditioning noise testing, thus solving the aforementioned problems.

[0004] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A semi-anechoic chamber measurement system for air conditioning noise testing includes: The conversion analysis unit is used to make a miniature sound generator in the target location emit a reference sound wave before the target object is activated. The microphone in the target location receives the reference sound wave and converts the capacitance change caused by the reference sound wave into a reference voltage sequence that varies with time. The sound pressure of the reference sound wave and the reference voltage sequence are analyzed to obtain a reference conversion efficiency value representing the initial sound pressure and capacitance. The collaborative calibration unit is used to acquire the temperature in the target location in real time. During the target object test, it repeatedly emits reference sound waves at fixed time intervals and receives the corresponding real-time calibration voltage signal sequence. It performs collaborative analysis on temperature difference, voltage difference and reference conversion efficiency value, and generates a thermally sensitive attenuation factor that represents the effect of temperature change on microphone diaphragm elastic modulus change and electret charge attenuation on sound pressure-capacitance conversion efficiency. The attenuation compensation unit is used to continuously acquire the original voltage sequence caused by the noise of the target object, and perform inverse compensation on the original voltage sequence according to the thermally sensitive attenuation factor to obtain the dynamic capacitance response value sequence corresponding to the capacitance change as the temperature rises and the actual sound pressure decreases. The judgment unit is used to analyze the degree of electromagnetic noise suppression based on the original voltage sequence and the dynamic capacitance response value sequence, and to obtain measurement indicators to determine whether the effects of temperature drift and electromagnetic coupling have been eliminated during the current measurement process.

[0005] Furthermore, the miniature sound generator includes: The miniature speaker can be any one of a MEMS loudspeaker, a miniature piezoelectric ceramic sound generator, or a miniature electrodynamic loudspeaker.

[0006] Furthermore, by analyzing the sound pressure and reference voltage sequences of the reference sound wave, a reference conversion efficiency value representing the initial sound pressure and capacitance is obtained, including: Based on the sound pressure and reference voltage sequence of the reference sound wave, the response delay of the microphone diaphragm is analyzed to obtain the sound pressure-capacitance coherence coefficient, which represents the degree of hysteresis of the microphone diaphragm response.

[0007] Furthermore, by analyzing the sound pressure and reference voltage sequences of the reference sound wave, a reference conversion efficiency value representing the initial sound pressure and capacitance is obtained, which also includes: Deviation analysis was performed on the reference voltage sequence to obtain the electret charge response factor, which represents the influence of the electret surface charge trapping state on the conversion efficiency. By fusing the sound pressure-capacitance coherence coefficient and the electret charge response factor, and combining this with the sound pressure of a reference sound wave, a reference conversion efficiency value representing the initial sound pressure and capacitance is obtained.

[0008] Furthermore, a synergistic analysis of temperature differences, voltage differences, and reference conversion efficiency values ​​is performed to generate a thermally sensitive attenuation factor representing the impact of temperature-induced changes in the microphone diaphragm's elastic modulus and electret charge attenuation on the sound pressure-capacitance conversion efficiency. This factor includes: The difference between the current temperature and the temperature before startup, the ratio of the fundamental amplitude of the real-time calibration voltage signal sequence to the fundamental amplitude of the reference voltage sequence, and the reference conversion efficiency value are jointly calculated to obtain the elastic modulus shift factor, which represents the effect of temperature change on the elastic modulus of the microphone diaphragm. Energy analysis was performed on the real-time calibration voltage signal sequence to obtain the charge distortion coefficient, which represents the effect of the conversion caused by the thermal decay of the electret charge.

[0009] Furthermore, a synergistic analysis of temperature differences, voltage differences, and reference conversion efficiency values ​​is performed to generate a thermally sensitive attenuation factor representing the impact of temperature-induced changes in the microphone diaphragm's elastic modulus and electret charge attenuation on the sound pressure-capacitance conversion efficiency. This also includes: Based on the real-time calibration voltage signal sequence and the reference voltage sequence, the phase difference between the two is analyzed as a function of temperature difference, and the thermal voltage gradient value representing the phase hysteresis characteristic between sound pressure and capacitance under temperature drift is obtained. For the real-time calibration voltage signal sequence and the reference voltage sequence, the temperature difference between the current temperature and the temperature before startup is calculated to obtain the thermal noise modulation index, which represents the degree of thermal noise modulation caused by the change in the elastic modulus of the diaphragm.

[0010] Furthermore, a synergistic analysis of temperature differences, voltage differences, and reference conversion efficiency values ​​is performed to generate a thermally sensitive attenuation factor representing the impact of temperature-induced changes in the microphone diaphragm's elastic modulus and electret charge attenuation on the sound pressure-capacitance conversion efficiency. This also includes: The elastic modulus offset factor, charge distortion coefficient, thermal voltage gradient value and thermal noise modulation index are fused together, and the fused value is calculated with the sound pressure of the reference sound wave to obtain the conversion attenuation value representing the degree of degradation of the sound pressure-capacitance conversion efficiency under the combined thermal effect. The conversion attenuation value was analyzed to generate a thermally sensitive attenuation factor that represents the effect of temperature changes on the microphone diaphragm elastic modulus and electret charge attenuation on the sound pressure-capacitive conversion efficiency.

[0011] Furthermore, by inversely compensating the original voltage sequence based on the thermal sensitivity attenuation factor, a dynamic capacitance response sequence corresponding to the capacitance change as the temperature rises and the actual sound pressure decreases is obtained, including: Based on the thermal sensitivity attenuation factor, an inverse mapping is applied to each sampling point of the original voltage sequence to obtain a compensated voltage sequence that represents the elimination of temperature-induced electrical variable distortion. Based on the compensation voltage sequence, the waveform of capacitance change corresponding to diaphragm displacement under acoustic pressure excitation is analyzed to obtain the dynamic capacitance response value sequence corresponding to the capacitance change of the real acoustic pressure that decreases with temperature rise.

[0012] Furthermore, based on the original voltage sequence and the dynamic capacitance response sequence, the degree of electromagnetic noise suppression is analyzed to obtain measurement indicators for determining whether the effects of temperature drift and electromagnetic coupling have been eliminated during the current measurement process, including: For the original voltage sequence and the dynamic capacitor response sequence, the sign consistency between the two is analyzed to obtain the electromagnetic coupling residual value that represents the electromagnetic coupling energy that has not been compensated.

[0013] Furthermore, based on the original voltage sequence and the dynamic capacitance response sequence, the degree of electromagnetic noise suppression is analyzed to obtain measurement indicators for determining whether the effects of temperature drift and electromagnetic coupling have been eliminated during the current measurement process. These indicators also include: The mutual information redundancy between the original voltage sequence and the dynamic capacitance response sequence is calculated. The mutual information redundancy is then fused with the electromagnetic coupling residual value to obtain a measurement index that determines whether the effects of temperature drift and electromagnetic coupling have been eliminated during the current measurement process.

[0014] In summary, the present invention has the following main beneficial effects: The conversion analysis unit controls a miniature microphone to emit a reference sound wave before the target object is activated. This wave is received by the microphone and converted into a reference voltage sequence. The reference conversion efficiency value is obtained by combining the sound pressure of the reference sound wave with the sound pressure analysis. This accurately captures the correspondence between the initial sound pressure and capacitance. At the same time, the accuracy of the reference calibration is further improved by fusion analysis of the sound pressure-capacitance coherence coefficient and the electret charge response factor. The collaborative calibration unit acquires the temperature of the target location in real time, repeats the calibration at fixed time intervals, and generates a thermally sensitive attenuation factor. This comprehensively reflects the combined effects of temperature changes on the microphone diaphragm elastic modulus and electret charge attenuation, effectively solving the problem of decreased sound pressure-capacitance conversion efficiency caused by temperature rise.

[0015] The attenuation compensation unit performs inverse compensation on the original voltage sequence through a thermally sensitive attenuation factor, restoring the dynamic capacitance response value sequence corresponding to the decrease in the true sound pressure when the temperature rises. This avoids further attenuation of the weak electrical signal amplitude corresponding to low noise. Finally, the judgment unit accurately determines the degree of elimination of temperature drift and electromagnetic coupling effects by analyzing the sign consistency and mutual information redundancy of the original voltage sequence and the dynamic capacitance response value sequence. This effectively suppresses electromagnetic noise coupling, prevents the true sound pressure from being masked by interference signals, ensures the accuracy of air conditioning noise test data, and fully adapts to the high-precision testing requirements of semi-anechoic chambers. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the semi-anechoic chamber measurement system for air conditioning noise testing according to the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] refer to Figure 1 A semi-anechoic chamber measurement system for air conditioning noise testing, comprising: The conversion analysis unit is used to make a miniature sound generator in the target location emit a reference sound wave before the target object is activated. The microphone in the target location receives the reference sound wave and converts the capacitance change caused by the reference sound wave into a reference voltage sequence that varies with time. The sound pressure of the reference sound wave and the reference voltage sequence are analyzed to obtain a reference conversion efficiency value representing the initial sound pressure and capacitance. The target object is an air conditioner, and the target location is a semi-anechoic chamber. The collaborative calibration unit is used to acquire the temperature in the target location in real time. During the target object test, it repeatedly emits reference sound waves at fixed time intervals and receives the corresponding real-time calibration voltage signal sequence. It performs collaborative analysis on temperature difference, voltage difference and reference conversion efficiency value, and generates a thermally sensitive attenuation factor that represents the effect of temperature change on microphone diaphragm elastic modulus change and electret charge attenuation on sound pressure-capacitance conversion efficiency. The attenuation compensation unit is used to continuously acquire the original voltage sequence caused by the noise of the target object, and perform inverse compensation on the original voltage sequence according to the thermally sensitive attenuation factor to obtain the dynamic capacitance response value sequence corresponding to the capacitance change as the temperature rises and the actual sound pressure decreases. The judgment unit is used to analyze the degree of electromagnetic noise suppression based on the original voltage sequence and the dynamic capacitance response value sequence, and to obtain measurement indicators to determine whether the effects of temperature drift and electromagnetic coupling have been eliminated during the current measurement process.

[0019] In one embodiment, the miniature sound generator includes: The miniature speaker can be any one of the following: MEMS loudspeaker, miniature piezoelectric ceramic sound generator, or miniature electrodynamic loudspeaker.

[0020] In one embodiment, the sound pressure and reference voltage sequence of the reference sound wave are analyzed to obtain a reference conversion efficiency value representing the initial sound pressure and capacitance, including: Based on the sound pressure and reference voltage sequences of the reference sound wave, the response delay of the microphone diaphragm is analyzed to obtain the sound pressure-capacitance coherence coefficient, which represents the degree of hysteresis of the microphone diaphragm response. Specifically, for the sound pressure of the reference sound wave, a sound pressure sequence of the same length as the reference voltage sequence is taken. For each positive zero-crossing moment in the sound pressure sequence that changes from negative to positive, and the corresponding positive zero-crossing moment in the reference voltage sequence, the time difference between the voltage zero-crossing moment and the sound pressure zero-crossing moment in each cycle is calculated. Then, the average of the time differences in all cycles is calculated to obtain the average zero-crossing time difference. The period duration is taken as the reciprocal of the reference sound wave frequency. The average zero-crossing time difference is divided by the period duration to obtain the hysteresis phase ratio. The hysteresis phase ratio represents the proportion of the diaphragm response delay to the entire period. Subtracting the hysteresis phase ratio from 1 yields the sound pressure-capacitance coherence coefficient, which represents the degree of hysteresis in the microphone diaphragm response.

[0021] In one embodiment, analyzing the sound pressure and reference voltage sequence of the reference sound wave to obtain a reference conversion efficiency value representing the initial sound pressure and capacitance further includes: Deviation analysis is performed on the reference voltage sequence to obtain the electret charge response factor, which represents the influence of the electret surface charge trapping state on the conversion efficiency. Specifically, the reference voltage sequence is divided into segments of equal length according to the duration of the reference acoustic wave period, with each segment corresponding to a complete acoustic wave period. For the voltage in each period, the arithmetic mean of the positive voltage amplitude and the arithmetic mean of the negative voltage amplitude in that period are calculated respectively. The sum of the absolute values ​​of the two arithmetic means is taken as the total response amplitude of that period. The difference between the absolute values ​​of the two arithmetic means is then calculated as the asymmetric deviation of that period. The asymmetric deviations of all periods are arranged in chronological order to obtain the deviation sequence. The local slope of each point is calculated using the three-point linear regression method on the deviation sequence: a straight line is fitted to the point and its three adjacent points, and the slope of the straight line is taken as the instantaneous drift rate of the point. The absolute values ​​of all instantaneous drift rates are summed and divided by the number of points to obtain the average drift rate. Divide the average drift rate of change by the root mean square value of the entire reference voltage sequence and normalize the result to the 0-1 interval to obtain the electret charge response factor. The electret charge response factor is used to represent the influence of the electret surface charge trapping state on the conversion efficiency.

[0022] The sound pressure-capacitance coherence coefficient and electret charge response factor are fused and analyzed in conjunction with the sound pressure of the reference sound wave to obtain a reference conversion efficiency value representing the initial sound pressure and capacitance. Specifically, the sound pressure-capacitance coherence coefficient is multiplied by 1 and the difference between it and the electret charge response factor to obtain a comprehensive attenuation factor. The comprehensive attenuation factor mainly reflects the dual weakening effect of hysteresis and drift on the sound pressure-capacitance conversion. The root mean square value of the reference voltage sequence is extracted to obtain the effective voltage value. The sound pressure value of the reference sound wave is used as the sound pressure reference value. The effective voltage value is divided by the sound pressure reference value to obtain the apparent efficiency. The apparent efficiency is divided by the comprehensive attenuation factor, and the calculation result is normalized to the 0-1 interval to obtain the reference conversion efficiency value representing the initial sound pressure and capacitance.

[0023] By analyzing the sound pressure and reference voltage sequences of the reference sound wave, the sound pressure-capacitance coherence coefficient and electret charge response factor are calculated respectively. The sound pressure-capacitance coherence coefficient reflects the phase shift caused by the diaphragm response hysteresis, while the electret charge response factor mainly reflects the asymmetric drift caused by the charge trapping state on the electret surface. The two are then integrated into a comprehensive attenuation factor, which is used to correct the apparent efficiency, thereby obtaining a reference conversion efficiency value that represents the true conversion relationship between the initial sound pressure and capacitance. This reference conversion efficiency value can dynamically compensate for the efficiency decrease caused by changes in the diaphragm elastic modulus and charge attenuation, enabling accurate restoration of the amplitude of weak electrical signals, effectively suppressing coupling interference with electromagnetic noise of the test equipment, and improving the signal-to-noise ratio and accuracy of the measurement results in noise testing.

[0024] In one embodiment, a synergistic analysis is performed on temperature differences, voltage differences, and a reference conversion efficiency value to generate a thermally sensitive attenuation factor representing the impact of temperature-induced changes in the microphone diaphragm's elastic modulus and electret charge attenuation on the sound pressure-capacitive conversion efficiency. This includes: The difference between the current temperature and the initial temperature before startup, the ratio of the fundamental amplitude of the real-time calibration voltage signal sequence to the fundamental amplitude of the reference voltage sequence, and the reference conversion efficiency value are jointly calculated to obtain the elastic modulus shift factor, which represents the influence of temperature change on the elastic modulus of the microphone diaphragm. Specifically, this includes: obtaining the difference between the current temperature and the initial temperature before startup, and using the difference as the temperature change; dividing the fundamental amplitude extracted from the real-time calibration voltage signal sequence by the fundamental amplitude extracted from the reference voltage sequence to obtain the voltage attenuation value. Taking the natural logarithm of the voltage decay value yields the logarithmic decay, which in turn transforms the multiplicative decay into the additive decay. This aligns with the physical characteristic that changes in the diaphragm's elastic modulus lead to an exponential shift in sensitivity. Simultaneously, the absolute value of the temperature change is added to 0.01 to obtain the temperature amplitude. Adding this value to 0.01 here avoids the temperature amplitude being zero. Add the reference conversion efficiency value to 0.01 and multiply it by the temperature amplitude to obtain the temperature-efficiency joint value. Divide the logarithmic attenuation by the temperature-efficiency joint value and normalize the calculation result to the 0-1 interval to obtain the elastic modulus offset factor, which mainly represents the effect of temperature change on the elastic modulus of the microphone diaphragm.

[0025] Energy analysis is performed on the real-time calibration voltage signal sequence to obtain the charge distortion coefficient, which represents the effect of electret charge thermal decay on the conversion. Specifically, this includes: extracting the voltage of each complete cycle from the real-time calibration voltage signal sequence; for each cycle's sampling point sequence, first calculating the arithmetic mean of the sampling point sequence, and then subtracting this mean from each sampling point to obtain a zero-mean sequence; then calculating the ratio of the sum of squares of the sampling points in the first half of the zero-mean sequence to the sum of squares of the sampling points in the second half of the cycle to obtain the half-cycle energy ratio; the reference voltage sequence is calculated in the same way to obtain the reference half-cycle energy ratio. The difference between the real-time energy ratio and the reference half-cycle energy ratio in the same cycle is calculated. The mean of the differences in all cycles is calculated, and the mean is divided by the absolute value of the temperature change. The calculation result is normalized to the 0-1 interval, and the charge distortion coefficient representing the conversion effect caused by the thermal decay of electret charge can be obtained.

[0026] In one embodiment, a synergistic analysis of temperature differences, voltage differences, and a reference conversion efficiency value is performed to generate a thermally sensitive attenuation factor representing the impact of temperature-induced changes in the microphone diaphragm's elastic modulus and electret charge attenuation on the sound pressure-capacitive conversion efficiency. This also includes: Based on the real-time calibration voltage signal sequence and the reference voltage sequence, the phase difference between the two is analyzed as a function of temperature difference to obtain the thermal voltage gradient value representing the phase lag characteristic between sound pressure and capacitance under temperature drift. Specifically, this includes: within each cycle, for the positive zero-crossing point in the real-time calibration voltage sequence that changes from negative to positive, and the corresponding positive zero-crossing point in the reference voltage sequence, the difference between the real-time voltage zero-crossing point and the reference voltage zero-crossing point in the same cycle is calculated to obtain the relative zero-crossing time difference for that cycle, in seconds. Calculate the arithmetic mean of the relative zero-crossing time differences for all cycles to obtain the relative zero-crossing time difference value. Divide the relative zero-crossing time difference value by the period duration of the reference sound wave to obtain the average phase offset ratio. Dividing the average phase shift ratio by the absolute value of the temperature change yields the thermal voltage gradient value, which is mainly used to represent the phase hysteresis characteristics between the sound pressure and the capacitance under temperature drift.

[0027] For the real-time calibration voltage signal sequence and the reference voltage sequence, the thermal noise modulation index, representing the degree of thermal noise modulation caused by the change in the diaphragm's elastic modulus, is calculated by comparing the temperature difference between the current temperature and the temperature before startup. Specifically, this involves: dividing the real-time calibration voltage signal sequence and the reference voltage sequence into equal-length segments according to the duration of the reference acoustic wave period to obtain multiple periodic segments; calculating the mean value of the corresponding sampling points at the same position within each periodic segment (i.e., the same sampling point within each period), which is the template value; arranging multiple template values ​​to obtain the periodic average sequence; and subtracting the template value at the corresponding position from each sampling point of the real-time calibration voltage signal sequence and the reference voltage sequence to obtain two residual sequences, namely the calibration residual sequence and the reference residual sequence. Calculate the root mean square values ​​of the calibration residual sequence and the reference residual sequence respectively. That is, square the result of the sum of the squares of each sampling point, divide by the total number of points, and take the square root to obtain the calibration thermal noise energy and the reference thermal noise energy. Divide the calibration thermal noise energy by the reference thermal noise energy to obtain the energy ratio. Take the natural logarithm of the energy ratio to obtain the logarithmic energy offset. Dividing the logarithmic energy offset by the temperature change and normalizing the result to the 0-1 range yields the thermal noise modulation index. The thermal noise modulation index mainly reflects the logarithmic relative rate of change of thermal noise energy under temperature change, and it can directly reflect the degree of thermal noise modulation caused by the change of the diaphragm's elastic modulus.

[0028] In one embodiment, a synergistic analysis of temperature differences, voltage differences, and a reference conversion efficiency value is performed to generate a thermally sensitive attenuation factor representing the impact of temperature-induced changes in the microphone diaphragm's elastic modulus and electret charge attenuation on the sound pressure-capacitive conversion efficiency. This also includes: The elastic modulus offset factor, charge distortion coefficient, thermal voltage gradient value and thermal noise modulation index are fused together. After fusion, the sound pressure of the reference sound wave is calculated to obtain the conversion attenuation value, which represents the degree of degradation of the sound pressure-capacitance conversion efficiency under the comprehensive thermal effect. Specifically, the thermal voltage gradient value is normalized to the 0-1 range to make it a dimensionless value, and the heat value is obtained. The elastic modulus offset factor, charge distortion coefficient, thermal value, and thermal noise modulation index are regarded as vector components in four-dimensional space. Their Euclidean modulus is calculated as the square root of the sum of the square of the elastic modulus offset factor, the square of the charge distortion coefficient, the square of the thermal value, and the square of the thermal noise modulation index. This Euclidean modulus represents the combined strength of the four degradation factors. Since the maximum value of each component is 1, the maximum value of the modulus is the square root of four, i.e., the value 2. Divide the Euclidean modulus by 2 and normalize the calculation result to the 0-1 range to obtain the conversion attenuation value, which represents the degree of degradation of the sound pressure-capacitor conversion efficiency under the combined thermal effect. The closer the conversion attenuation value is to 1, the more severe the degradation of the sound pressure-capacitor conversion efficiency caused by the combined thermal effect.

[0029] The conversion attenuation value is analyzed to generate a thermally sensitive attenuation factor that represents the impact of temperature changes on the microphone diaphragm's elastic modulus and electret charge attenuation on the sound pressure-capacitor conversion efficiency. Specifically, this involves calculating an exponential function with the natural constant e as the base and the conversion attenuation value as the exponent, i.e., e raised to the power of the conversion attenuation value, to obtain the thermally sensitive attenuation factor. When the conversion attenuation value is 0, the thermally sensitive attenuation factor equals 1; when the conversion attenuation value is 1, the thermally sensitive attenuation factor equals the natural constant e. The thermally sensitive attenuation factor represents the inverse compensation factor required to restore the original sound pressure-capacitor conversion relationship after a temperature change. The more severe the degradation, the larger the compensation factor, exhibiting an exponential growth relationship. The thermally sensitive attenuation factor fully reflects the impact of temperature changes on the microphone diaphragm's elastic modulus and electret charge attenuation on the sound pressure-capacitor conversion efficiency.

[0030] By synergistically analyzing temperature differences, voltage differences, and reference conversion efficiency values, a thermally sensitive attenuation factor is generated. This factor reflects the drift of diaphragm stiffness with temperature changes. The charge distortion coefficient is used to determine the waveform half-cycle energy imbalance caused by electret charge thermal decay. Simultaneously, the thermal voltage gradient value is calculated to reflect the phase lag characteristics under temperature drift. Finally, the thermally sensitive attenuation factor is obtained. This factor accurately reflects the degree of degradation of acoustic pressure-capacitance conversion efficiency after temperature rise, effectively suppressing signal attenuation and electromagnetic noise coupling caused by changes in diaphragm elastic modulus and charge decay, thus improving the measurement accuracy of high-noise tests.

[0031] In one embodiment, the original voltage sequence is inversely compensated according to the thermal sensitivity attenuation factor to obtain a dynamic capacitance response value sequence corresponding to the capacitance change as the temperature rises and the actual sound pressure decreases, including: Based on the thermal sensitivity attenuation factor, an inverse mapping is applied to each sampling point of the original voltage sequence to obtain a compensated voltage sequence that represents the elimination of temperature-induced electrical variable distortion. Specifically, this includes: obtaining the instantaneous amplitude of each sampling point in the original voltage sequence, and calculating the arithmetic mean of the amplitudes of the three adjacent points before and after the sampling point to obtain the local background amplitude; then calculating the ratio of the local background amplitude to the overall root mean square value of the original voltage sequence to obtain the local modulation coefficient. The local modulation coefficient mainly reflects the degree of deviation of the current sampling point from the global average level. Multiplying the thermal sensitivity attenuation factor by the local modulation coefficient yields the dynamic compensation coefficient. Multiplying each sampling point of the original voltage sequence by the corresponding dynamic compensation coefficient yields the compensated voltage sequence representing the elimination of temperature-induced electrical variable distortion.

[0032] Based on the compensation voltage sequence, the waveform of capacitance change corresponding to diaphragm displacement under sound pressure excitation is analyzed to obtain the dynamic capacitance response value sequence corresponding to the capacitance change caused by the decrease in actual sound pressure due to temperature rise. Specifically, this includes: obtaining the instantaneous voltage value of each sampling point in the compensation voltage sequence, and calculating the arithmetic mean of the compensation voltage sequence as the DC bias component. For each sampling point, the instantaneous voltage value is subtracted from the DC bias component to obtain the AC voltage component. The AC voltage component mainly reflects the capacitance change modulation caused by sound pressure. The reference sensitivity coefficient is obtained by multiplying the overall root mean square value of the reference voltage sequence by the reference conversion efficiency value and then dividing it by the sound pressure value of the reference sound wave. The reference sensitivity coefficient mainly reflects the conversion relationship between sound pressure and voltage under the initial state. For each sampling point of the compensation voltage sequence, the AC voltage component of the sampling point is multiplied by the reference conversion efficiency value and then divided by the overall root mean square value of the reference voltage sequence to obtain the relative change value of the capacitance corresponding to the sampling point. All relative change values ​​of capacitance are arranged in time order to obtain the capacitance waveform sequence. The capacitor waveform sequence is subjected to a high-pass filter with a cutoff frequency set to one-tenth of the reference sound wave frequency. This filter removes the ultra-low frequency baseline drift caused by temperature and charge attenuation, retaining only the effective capacitance change signal caused by sound pressure vibration. The output filtered sequence is the dynamic capacitance response value sequence, which directly reflects the capacitance change caused by the diaphragm displacement excited by the corresponding temperature rise and decrease in the actual sound pressure.

[0033] The original voltage sequence is inversely compensated by a thermally sensitive attenuation factor to obtain local modulation coefficients. Then, the sampling points are corrected point by point by a dynamic compensation coefficient to effectively eliminate electrical variable distortion caused by temperature. The AC voltage component is extracted from the compensated voltage sequence. Combined with the reference conversion efficiency value, the overall root mean square value of the reference voltage sequence, and the sound pressure value of the reference sound wave, the relative change value of capacitance is obtained. After high-pass filtering to remove ultra-low frequency baseline drift, the dynamic capacitance response value sequence is finally obtained. The dynamic capacitance response value sequence can directly reflect the capacitance change caused by the diaphragm displacement corresponding to the decrease in real sound pressure due to temperature rise. This accurately restores the sound pressure signal weakened by thermal effects, avoids further attenuation of low noise amplitude, reduces the risk of coupling with electromagnetic noise of the test equipment, and ensures the test effect of air conditioning noise.

[0034] In one embodiment, based on the original voltage sequence and the dynamic capacitance response value sequence, the degree of electromagnetic noise suppression is analyzed to obtain measurement indicators for determining whether the effects of temperature drift and electromagnetic coupling have been eliminated during the current measurement process, including: For the original voltage sequence and the dynamic capacitor response value sequence, the sign consistency of the two is analyzed to obtain the electromagnetic coupling residual value that represents the electromagnetic coupling energy that has not been compensated. Specifically, the original voltage sequence and the dynamic capacitor response value sequence are respectively zero-mean processed, that is, their respective values ​​are subtracted from their overall arithmetic mean. Using one-tenth of the reference acoustic wave period as the window length, the original voltage sequence and the dynamic capacitor response value sequence are synchronously divided into multiple overlapping windows, with adjacent windows overlapping by half the length. Within each window, the zero-mean product of the two sequences is compared point by point: if the product is greater than zero, it is marked as having the same sign; otherwise, it is marked as having different signs. The proportion of points with the same sign to the total number of points in the window is counted to obtain the sign consistency coefficient of the window. Calculate the absolute difference of the sign consistency coefficients between adjacent windows to obtain the difference sequence, calculate the root mean square value of the difference sequence as the fluctuation intensity; at the same time, calculate the arithmetic mean of the sign consistency coefficient sequence and use it as the average consistency benchmark. Divide the fluctuation intensity by the average consistency benchmark and normalize the calculation result to the 0-1 range to obtain the electromagnetic coupling residual value that represents the electromagnetic coupling energy that has not been compensated.

[0035] In one embodiment, based on the original voltage sequence and the dynamic capacitance response value sequence, the degree of electromagnetic noise suppression is analyzed to obtain measurement indicators for determining whether the effects of temperature drift and electromagnetic coupling have been eliminated during the current measurement process. This also includes: The mutual information redundancy of the original voltage sequence and the dynamic capacitance response value sequence is calculated. The mutual information redundancy and the electromagnetic coupling residual value are fused to obtain the measurement index for determining whether the influence of temperature drift and electromagnetic coupling in the current measurement process has been eliminated. Specifically, the original voltage sequence and the dynamic capacitance response value sequence are respectively zero-mean processed, and then each is divided into sixteen intervals according to the amplitude range. The probability of the sampling point in each sequence falling into each interval is calculated to obtain the marginal probability. At the same time, the probability of the two sequences jointly falling into each interval pair is calculated to obtain the joint probability. For all interval pairs, the joint probability is multiplied by the logarithm of the product of the joint probability and the marginal probability (base 2), and then summed to obtain the mutual information value. For the original voltage sequence, each marginal probability is multiplied by the logarithm of its own marginal probability (base 2), the negative is taken, and the sum is obtained to obtain the sequence entropy. The mutual information value is divided by the sequence entropy, and the calculation result is normalized to the 0-1 interval to obtain the mutual information ratio. Subtracting the mutual information ratio from 1 gives the redundancy, which is between 0 and 1. The closer the redundancy is to 1, the less information is shared between the two sequences, meaning that the dynamic capacitor response value sequence failed to resolve the information in the original voltage sequence and the electromagnetic coupling residue was more severe. The redundancy is multiplied by the residual value of electromagnetic coupling, and the calculation result is normalized to the 0-1 interval to obtain the measurement index. When the measurement index is 0, it means that the temperature drift and electromagnetic coupling effects have been completely eliminated; otherwise, it means that the temperature drift and electromagnetic coupling effects have not been completely eliminated.

[0036] By analyzing the sign consistency between the original voltage sequence and the dynamic capacitor response value sequence, the sign consistency coefficient is obtained. Then, the electromagnetic coupling residual value is calculated, which can represent the uncompensated electromagnetic coupling energy. The mutual information redundancy between the original voltage sequence and the dynamic capacitor response value sequence is analyzed. The redundancy and the electromagnetic coupling residual value are fused to obtain the measurement index. When the measurement index is 0, it means that the temperature drift and electromagnetic coupling effects have been completely eliminated. Otherwise, it means that the temperature drift and electromagnetic coupling effects have not been completely eliminated. This scheme can avoid the sound pressure being masked by the interference signal and ensure the test effect of air conditioner noise.

[0037] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A semi-anechoic chamber measurement system for air conditioning noise testing, characterized in that, include: The conversion analysis unit is used to make a miniature sound generator in the target location emit a reference sound wave before the target object is activated. The microphone in the target location receives the reference sound wave and converts the capacitance change caused by the reference sound wave into a reference voltage sequence that varies with time. The sound pressure of the reference sound wave and the reference voltage sequence are analyzed to obtain a reference conversion efficiency value representing the initial sound pressure and capacitance. The collaborative calibration unit is used to acquire the temperature in the target location in real time. During the target object test, it repeatedly emits reference sound waves at fixed time intervals and receives the corresponding real-time calibration voltage signal sequence. It performs collaborative analysis on temperature difference, voltage difference and reference conversion efficiency value, and generates a thermally sensitive attenuation factor that represents the effect of temperature change on microphone diaphragm elastic modulus change and electret charge attenuation on sound pressure-capacitance conversion efficiency. The attenuation compensation unit is used to continuously acquire the original voltage sequence caused by the noise of the target object, and perform inverse compensation on the original voltage sequence according to the thermally sensitive attenuation factor to obtain the dynamic capacitance response value sequence corresponding to the capacitance change as the temperature rises and the actual sound pressure decreases. The judgment unit is used to analyze the degree of electromagnetic noise suppression based on the original voltage sequence and the dynamic capacitance response value sequence, and to obtain measurement indicators to determine whether the effects of temperature drift and electromagnetic coupling have been eliminated during the current measurement process.

2. The semi-anechoic chamber measurement system for air conditioning noise testing according to claim 1, characterized in that, Miniature sound generator, including: The miniature speaker can be any one of a MEMS loudspeaker, a miniature piezoelectric ceramic sound generator, or a miniature electrodynamic loudspeaker.

3. The semi-anechoic chamber measurement system for air conditioning noise testing according to claim 1, characterized in that, By analyzing the sound pressure and reference voltage sequences of the reference sound wave, the reference conversion efficiency value representing the initial sound pressure and capacitance is obtained, including: Based on the sound pressure and reference voltage sequence of the reference sound wave, the response delay of the microphone diaphragm is analyzed to obtain the sound pressure-capacitance coherence coefficient, which represents the degree of hysteresis of the microphone diaphragm response.

4. The semi-anechoic chamber measurement system for air conditioning noise testing according to claim 3, characterized in that, Analyzing the sound pressure and reference voltage sequences of the reference sound wave yields a reference conversion efficiency value representing the initial sound pressure versus capacitance, which also includes: Deviation analysis was performed on the reference voltage sequence to obtain the electret charge response factor, which represents the influence of the electret surface charge trapping state on the conversion efficiency. By fusing the sound pressure-capacitance coherence coefficient and the electret charge response factor, and combining this with the sound pressure of a reference sound wave, a reference conversion efficiency value representing the initial sound pressure and capacitance is obtained.

5. The semi-anechoic chamber measurement system for air conditioning noise testing according to claim 4, characterized in that, A synergistic analysis of temperature differences, voltage differences, and reference conversion efficiency values ​​is performed to generate a thermally sensitive attenuation factor representing the impact of temperature-induced changes in microphone diaphragm elastic modulus and electret charge attenuation on sound pressure-capacitance conversion efficiency. This factor includes: The difference between the current temperature and the temperature before startup, the ratio of the fundamental amplitude of the real-time calibration voltage signal sequence to the fundamental amplitude of the reference voltage sequence, and the reference conversion efficiency value are jointly calculated to obtain the elastic modulus shift factor, which represents the effect of temperature change on the elastic modulus of the microphone diaphragm. Energy analysis was performed on the real-time calibration voltage signal sequence to obtain the charge distortion coefficient, which represents the effect of the conversion caused by the thermal decay of the electret charge.

6. The semi-anechoic chamber measurement system for air conditioning noise testing according to claim 5, characterized in that, A synergistic analysis of temperature differences, voltage differences, and reference conversion efficiency values ​​is performed to generate a thermally sensitive attenuation factor representing the impact of temperature-induced changes in microphone diaphragm elastic modulus and electret charge attenuation on sound pressure-capacitance conversion efficiency. This also includes: Based on the real-time calibration voltage signal sequence and the reference voltage sequence, the phase difference between the two is analyzed as a function of temperature difference, and the thermal voltage gradient value representing the phase hysteresis characteristic between sound pressure and capacitance under temperature drift is obtained. For the real-time calibration voltage signal sequence and the reference voltage sequence, the temperature difference between the current temperature and the temperature before startup is calculated to obtain the thermal noise modulation index, which represents the degree of thermal noise modulation caused by the change in the elastic modulus of the diaphragm.

7. The semi-anechoic chamber measurement system for air conditioning noise testing according to claim 6, characterized in that, A synergistic analysis of temperature differences, voltage differences, and reference conversion efficiency values ​​is performed to generate a thermally sensitive attenuation factor representing the impact of temperature-induced changes in microphone diaphragm elastic modulus and electret charge attenuation on sound pressure-capacitance conversion efficiency. This also includes: The elastic modulus offset factor, charge distortion coefficient, thermal voltage gradient value and thermal noise modulation index are fused together, and the fused value is calculated with the sound pressure of the reference sound wave to obtain the conversion attenuation value representing the degree of degradation of the sound pressure-capacitance conversion efficiency under the combined thermal effect. The conversion attenuation value was analyzed to generate a thermally sensitive attenuation factor that represents the effect of temperature changes on the microphone diaphragm elastic modulus and electret charge attenuation on the sound pressure-capacitive conversion efficiency.

8. The semi-anechoic chamber measurement system for air conditioning noise testing according to claim 7, characterized in that, By inversely compensating the original voltage sequence using a thermally sensitive attenuation factor, a dynamic capacitance response sequence corresponding to the capacitance change as the actual sound pressure decreases with increasing temperature is obtained, including: Based on the thermal sensitivity attenuation factor, an inverse mapping is applied to each sampling point of the original voltage sequence to obtain a compensated voltage sequence that represents the elimination of temperature-induced electrical variable distortion. Based on the compensation voltage sequence, the waveform of capacitance change corresponding to diaphragm displacement under acoustic pressure excitation is analyzed to obtain the dynamic capacitance response value sequence corresponding to the capacitance change of the real acoustic pressure that decreases with temperature rise.

9. The semi-anechoic chamber measurement system for air conditioning noise testing according to claim 8, characterized in that, Based on the original voltage sequence and the dynamic capacitance response sequence, the degree of electromagnetic noise suppression is analyzed to obtain measurement indicators for determining whether the effects of temperature drift and electromagnetic coupling have been eliminated during the current measurement process, including: For the original voltage sequence and the dynamic capacitor response sequence, the sign consistency between the two is analyzed to obtain the electromagnetic coupling residual value that represents the electromagnetic coupling energy that has not been compensated.

10. The semi-anechoic chamber measurement system for air conditioning noise testing according to claim 9, characterized in that, Based on the original voltage sequence and the dynamic capacitance response sequence, the degree of electromagnetic noise suppression is analyzed to obtain measurement indicators for determining whether the effects of temperature drift and electromagnetic coupling have been eliminated during the current measurement process. These indicators also include: The mutual information redundancy between the original voltage sequence and the dynamic capacitance response sequence is calculated. The mutual information redundancy is then fused with the electromagnetic coupling residual value to obtain a measurement index that determines whether the effects of temperature drift and electromagnetic coupling have been eliminated during the current measurement process.

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