Precision calibration method for acoustic calibration device based on mobile phone

Abstract

The invention discloses a precision calibration method for a sound calibration device based on a mobile phone, and relates to the field of acoustic measurement technology. The powerful computing power of a mobile phone is utilized, and an algorithm is used to make the calibrator have relatively high precision. When a loudspeaker, a MEMS microphone, a coupling cavity, and a voltage display module are added, all functions of a traditional sound calibrator can be realized, and the cost is only tens of yuan. Moreover, calibration of any frequency point of 50Hz to 16kHz can be realized. The mobile phone is equipped with a temperature sensor and a barometer, and the frequency response can be automatically compensated according to the changes in temperature and air pressure. Even if a different mobile phone is replaced, as long as the amplitude of the generated signal is adjusted so that the voltage display module displays v volts, the sound pressure level output by the loudspeaker can be made the target value.

Description

Technical Field

[0001] The invention relates to the technical field of acoustic measurement, and in particular to a precision calibration method of an acoustic calibration device based on a mobile phone. Background Art

[0002] As modern noise pollution becomes more and more serious, many cities have launched noise prevention and control. Sound level meters, as instruments for noise measurement, are also being used more and more. In addition, the sensitivity and frequency response of the microphone on the sound level meter need to be tested every day to prevent the sensitivity from drifting too much. The sensitivity of the microphone is mainly detected by a sound calibrator. Since 2017, the sound level meter frequency-weighted sound signal test method recommended in the national sound level meter standard has added a multi-frequency sound calibrator detection method. However, there are relatively few multi-frequency sound calibrators on the market, and there are not many calibrators with multi-frequency and multi-amplitude sound pressure calibration. The existing sound calibrators are composed of single-chip microcomputers, amplifier circuits, analog-to-digital converters, buttons, microphones, etc., with complex structures and costs of thousands or even tens of thousands, which is very expensive and has a low cost-effectiveness in engineering applications. Summary of the invention

[0003] 1. Technical problem to be solved by the invention

[0004] In view of the above technical problems, the present invention provides an accuracy calibration method for a sound calibration device based on a mobile phone, which enables a simple sound calibrator with a cost of only tens of yuan to have an accuracy comparable to that of a professional sound calibrator.

[0005] 2. Technical solution

[0006] In order to solve the above problems, the technical solution provided by the present invention is: a precision calibration method of a sound calibration device based on a mobile phone, the sound calibration device comprises a mobile phone and a coupler, a microphone, a speaker and a voltage display module connected to the speaker are arranged inside the coupler, an earphone is connected to the output end of the mobile phone, the earphone output pin is connected to the speaker, and the earphone input pin is connected to the microphone, and the precision calibration method is specifically as follows:

[0007] (1) Calibrate the frequency response of the speaker and microphone respectively;

[0008] (2) The mobile phone performs temperature compensation on the speaker by calculating the temperature value; at the same time, the mobile phone performs air pressure compensation on the speaker by calculating the air pressure value;

[0009] (3) The mobile phone generates sinusoidal signals of different frequencies using formula (1), and the sinusoidal signals are played through the calibrated speaker;

[0010]

[0011] Among them, x is the sinusoidal signal, A is the amplitude, ω is the angular frequency, and φ is the initial phase angle;

[0012] (4) The microphone collects the feedback signal from the speaker and inputs it into the mobile phone. The mobile phone calculates the feedback signal into a sound pressure level. If the calculated sound pressure level is less than the target value, the A value in formula (1) is increased. Otherwise, the A value is decreased to ensure that the sound pressure level output by the speaker is the target value.

[0013] (5) Calibrate the output voltage of different mobile phones based on the target sound pressure level of the speaker output.

[0014] Optionally, the calibration of the output voltage of different mobile phones in step (5) includes the following steps:

[0015] (5.1) Place the standard microphone into the coupling cavity of the coupler at room temperature, and generate a standard calibration signal;

[0016] (5.2) Adjust the signal amplitude generated by the mobile phone so that the sound level meter connected to the standard microphone displays the target value;

[0017] (5.3) Check the voltage displayed by the voltage display module connected to the speaker, recorded as v volts;

[0018] (5.4) Adjust the signal amplitude generated by different mobile phones so that the voltage display module of each mobile phone displays v volts, that is, the sound pressure level output by the speaker can reach the target value.

[0019] Optionally, the calibration of the speaker and the microphone in step (1) is specifically as follows:

[0020] (1.1) Speaker frequency response calibration

[0021] (1.11) Place the standard microphone into the coupling cavity of the coupler at room temperature, and the mobile phone generates n calibration signals that need to be calibrated;

[0022] (1.12) After the sound level meter connected to the standard microphone reads the sound pressure level of n calibration signals, it takes the critical sound pressure level as the reference and records the difference between the sound pressure level at each frequency point and the critical sound pressure level;

[0023] (1.13) Replace N speakers of the same model, repeat step (1.12), and record the difference between the sound pressure level at each frequency point and the critical sound pressure level;

[0024] (1.14) Take the average value of N groups of data and input it into the mobile phone as the frequency response compensation parameter of each frequency point of the speaker;

[0025] (1.15) The mobile phone plays the calibration signal and adds different frequency signals to the frequency response compensation parameters of the corresponding frequencies to ensure that the signals of each calibration frequency emitted by the speaker are flat;

[0026] (1.2) Microphone frequency response calibration

[0027] (1.21) The mobile phone receives calibration signals of various frequencies through the microphone and calculates the sound pressure level. Formula (2) takes the critical sound pressure level as the benchmark and records the difference between the sound pressure level at each frequency point and the critical sound pressure level.

[0028] (1.22) Replace N microphones of the same model, repeat step (1.21), and record the difference between the sound pressure level at each frequency point and the critical sound pressure level.

[0029] (1.23) Take the average value of N groups of data and input it into the mobile phone as the frequency response compensation parameter of each frequency point of the microphone.

[0030] (1.24) When the mobile phone measures the sound pressure level of the feedback signal through the microphone, the microphone frequency response compensation parameter is added so that the frequency response of each calibration frequency measured by the microphone is flat;

[0031]

[0032] Where L is the sound pressure level, Pa is the measured sound pressure, n is the number of sound pressures over a period of time, and P0 is the reference 0 dB.

[0033] Optionally, the specific operation of temperature compensation for the speaker in step (2) is as follows:

[0034] (2.11) Place the standard microphone into the coupling cavity of the coupler, and then place the coupler into the ambient temperature box;

[0035] (2.12) The mobile phone sends calibration signals of n frequencies through the speaker, and receives the signals through the microphone and calculates the sound pressure level;

[0036] (2.13) Gradually adjust the temperature of the ambient temperature box, and record the sound pressure level measured by the microphone at each frequency during each adjustment;

[0037] (2.13) Replace N speakers of the same model and record the difference between each frequency point at different temperatures and the corresponding frequency point at room temperature;

[0038] (2.14) After taking the average of N groups of data, a set of compensation values ​​for each frequency point at different temperatures is obtained;

[0039] (2.15) Let y = a1x 2 +a2x+a3 is the temperature and compensation value function at a frequency, where x is the temperature and y is the compensated sound pressure level. The least square method is used to calculate a1, a2, and a3. The temperature compensation function of all frequency points is obtained by this method.

[0040] (2.16) During calibration, the mobile phone performs temperature compensation on each frequency point by substituting the measured temperature into the temperature compensation function of each frequency point.

[0041] Optionally, the specific operation of compensating the air pressure of the speaker in step (2) is as follows:

[0042] (2.21) Place the standard microphone into the coupling cavity of the coupler, place the coupler into the air pressure box, and the mobile phone sends calibration signals of n frequencies through the speaker, while receiving the signals through the microphone and calculating the sound pressure level;

[0043] (2.22) Gradually adjust the air pressure in the air pressure box and record the sound pressure level measured by the microphone at each frequency after each adjustment;

[0044] (2.23) Replace N speakers of the same model and record the difference between each frequency point under different air pressures and the corresponding frequency point under standard atmospheric pressure;

[0045] (2.24) After taking the average of N groups of data, a set of compensation values ​​of each frequency point under different air pressures is obtained;

[0046] (2.25) Let y = a1x 2 +a2x+a3 is the air pressure and compensation value function at a frequency, x is the air pressure, y is the compensated sound pressure level, a1, a2, a3 are calculated using the least squares method, and the air pressure compensation function of all frequency points is calculated using this method;

[0047] (2.26) During calibration, the mobile phone achieves accurate air pressure compensation by substituting the measured air pressure value into the air pressure compensation function at each frequency point.

[0048] Optionally, in the step (2.16), a temperature sensor is provided inside the mobile phone, and the mobile phone measures the temperature value through the temperature sensor.

[0049] Optionally, in the step (2.26), a barometer is provided inside the mobile phone, and the mobile phone measures the air pressure value through the barometer.

[0050] Optionally, in the step (2.26), a positioning system is provided inside the mobile phone, and the current altitude is obtained through the positioning system, and g is obtained through the gravity accelerometer of the mobile phone, and the air pressure value at the current altitude is calculated by substituting it into formula (3), and then the air pressure value is substituted into the air pressure compensation function of each frequency point to realize air pressure compensation;

[0051]

[0052] Among them, P is the air pressure, P0 is the standard atmospheric pressure, e is the natural constant, H is the altitude, g is the acceleration of gravity, M is the gas molecular weight 29, R is the constant 8.51, and T is the thermodynamic temperature.

[0053] 3. Beneficial effects

[0054] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0055] A proposed in the embodiment of the present application, at present, mobile phones have become a necessity for everyone to carry with them. The mobile phone is connected to the coupler through the earphone line to calibrate the coupler. The powerful computing power of the mobile phone is used to make the calibrator have a relatively high accuracy by using an algorithm. When a speaker, MEMS microphone, coupling cavity, and voltage display module are added, all the functions of the traditional sound calibrator can be realized. The cost is only tens of yuan, and the calibration of any frequency point from 50Hz to 16kHz can be realized. The mobile phone has a temperature sensor and a barometer, which can automatically compensate for the frequency response according to the temperature and air pressure changes. Even if a different mobile phone is replaced, as long as the amplitude of the generated signal is adjusted so that the voltage display module displays v volts, the sound pressure level output by the speaker can be made the target value. A mobile phone without a barometer can obtain the current altitude H through GPS, obtain g through the mobile phone gravity accelerometer, substitute it into formula (3) to calculate the air pressure value at the current altitude, and then substitute the air pressure value into the air pressure compensation function of each frequency point to achieve accurate air pressure compensation. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 This is a schematic diagram of the sound calibration device proposed by the present invention. DETAILED DESCRIPTION

[0057] In order to further understand the content of the present invention, the present invention is described in detail in conjunction with the accompanying drawings and embodiments.

[0058] The present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are only used to explain the relevant inventions, rather than to limit the invention. It should also be noted that, for the convenience of description, only the parts related to the invention are shown in the accompanying drawings. The words "first", "second", etc. described in the present invention are set for the convenience of describing the technical solution of the present invention, and have no specific limiting effect. They are all general references and do not constitute a limiting effect on the technical solution of the present invention. It should be noted that, in the absence of conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. In the description of the present invention, it should be noted that the orientation or position relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. Unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be a connection between the insides of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. Multiple technical solutions in the same embodiment, and multiple technical solutions in different embodiments, can be arranged and combined to form new technical solutions without contradictions or conflicts, all of which are within the scope of protection required by the present invention.

[0059] Combined with Figure 1 The present invention discloses a precision calibration method of a sound calibration device based on a mobile phone, wherein the sound calibration device comprises a mobile phone and a coupler, wherein a microphone, a speaker and a voltage display module connected to the speaker are arranged inside the coupler, an earphone is connected to the output end of the mobile phone, the earphone output pin is connected to the speaker, and the earphone input pin is connected to the microphone, and the sound calibration method is specifically as follows:

[0060] (1) Calibrate the frequency response of the speaker and microphone respectively;

[0061] (2) The mobile phone performs temperature compensation on the speaker by calculating the temperature value; at the same time, the mobile phone performs air pressure compensation on the speaker by calculating the air pressure value;

[0062] (3) The mobile phone generates sinusoidal signals of different frequencies using formula (1), and the sinusoidal signals are played through the calibrated speaker;

[0063]

[0064] Among them, x is the sinusoidal signal, A is the amplitude, ω is the angular frequency, and φ is the initial phase angle;

[0065] (4) The microphone collects the feedback signal from the speaker and inputs it into the mobile phone. The mobile phone calculates the feedback signal into a sound pressure level. If the calculated sound pressure level is less than the target value, the A value in formula (1) is increased. Otherwise, the A value is decreased to ensure that the sound pressure level output by the speaker is the target value.

[0066] (5) Calibrate the output voltage of different mobile phones based on the target sound pressure level of the speaker output.

[0067] The microphone is a MEMS microphone, and the target value of the sound pressure level is 94 dB. In other embodiments, the target value of the sound pressure level may be 90 dB, 92 dB, 96 dB, or 98 dB.

[0068] At present, mobile phones have become a necessity for everyone to carry with them. Mobile phones are connected to couplers through earphone cables to calibrate couplers. By using the powerful computing power of mobile phones, algorithms are used to make the calibrator have relatively high accuracy. When combined with speakers, MEMS microphones, coupling cavities, and voltage display modules, all the functions of traditional sound calibrators can be realized. The cost is only a few dozen yuan, and calibration of any frequency point from 50Hz to 16kHz can be realized. This is because the attenuation of ordinary MEMS microphones outside 50Hz-16kHz is relatively large, and even if compensation is made, the effect is not very good. In addition, mobile phones have built-in temperature sensors and barometers, which can automatically compensate for frequency response according to temperature and air pressure changes. Even if different mobile phones are replaced, as long as the amplitude of the generated signal is adjusted so that the voltage display module displays v volts, the sound pressure level output by the speaker can be made the target value. Mobile phones without barometers can obtain the current altitude H through GPS, obtain g through the mobile phone gravity accelerometer, substitute them into formula (3) to calculate the air pressure value at the current altitude, and then substitute the air pressure value into the air pressure compensation function at each frequency point to achieve accurate air pressure compensation.

[0069] Furthermore, since the voltage reference output by the headphone output port of different mobile phones is different, it is necessary to first determine the voltage value output by the headphone port of the mobile phone when the speaker emits a calibrated sound pressure level of 94dB. The steps are as follows:

[0070] (5.1) Place the standard microphone into the coupling cavity of the coupler at room temperature of 25°C, and the mobile phone generates a standard calibration signal;

[0071] (5.2) Adjust the signal amplitude generated by the mobile phone so that the sound level meter connected to the standard microphone displays the target value;

[0072] (5.3) Check the voltage displayed by the voltage display module connected to the speaker, recorded as v volts;

[0073] (5.4) Adjust the signal amplitude generated by different mobile phones so that the voltage display module of each mobile phone displays v volts, that is, the sound pressure level output by the speaker can reach the target value.

[0074] Here, the standard calibration signal is 1000 Hz. In other embodiments, the calibration signal generated by the mobile phone may be 900 Hz, 950 Hz, 1050 Hz, 1100 Hz or other values. Normal temperature may also refer to 20° or 30°.

[0075] Furthermore, since the speaker and microphone are both civilian components, the frequency response cannot be flat, so the frequency response of both the speaker and the microphone needs to be calibrated. The steps are as follows:

[0076] (1.1) Speaker frequency response calibration

[0077] (1.11) Place the standard microphone into the coupling cavity of the coupler at room temperature, and the mobile phone generates n calibration signals that need to be calibrated;

[0078] (1.12) After the sound level meter connected to the standard microphone reads the sound pressure level of n calibration signals, it takes the critical sound pressure level as the reference and records the difference between the sound pressure level at each frequency point and the critical sound pressure level;

[0079] (1.13) Replace N speakers of the same model, repeat step (1.12), and record the difference between the sound pressure level at each frequency point and the critical sound pressure level;

[0080] (1.14) Take the average value of N groups of data and input it into the mobile phone as the frequency response compensation parameter of each frequency point of the speaker;

[0081] (1.15) The mobile phone plays the calibration signal and adds different frequency signals to the frequency response compensation parameters of the corresponding frequencies to ensure that the signals of each calibration frequency emitted by the speaker are flat;

[0082] (1.2) Microphone frequency response calibration

[0083] (1.21) The mobile phone receives calibration signals of various frequencies through the microphone and calculates the sound pressure level. Formula (2) takes the critical sound pressure level as the benchmark and records the difference between the sound pressure level at each frequency point and the critical sound pressure level.

[0084] (1.22) Replace N microphones of the same model, repeat step (1.21), and record the difference between the sound pressure level at each frequency point and the critical sound pressure level.

[0085] (1.23) Take the average value of N groups of data and input it into the mobile phone as the frequency response compensation parameter of each frequency point of the microphone.

[0086] (1.24) When the mobile phone measures the sound pressure level of the feedback signal through the microphone, the microphone frequency response compensation parameter is added so that the frequency response of each calibration frequency measured by the microphone is flat;

[0087]

[0088] Where L is the sound pressure level, Pa is the measured sound pressure, n is the number of sound pressures in a period of time, P0 is the reference 0dB, and the reference 0dB of the sound pressure level is 2*10 -5 Pa.

[0089] Here, the critical sound pressure level is 1000 Hz. In other embodiments, the critical sound pressure level may be 900 Hz, 950 Hz, 1050 Hz, 1100 Hz or other values.

[0090] Furthermore, since the MEMS microphone has good stability at different temperatures, but the performance of the speaker will be affected by temperature, the frequency response and sound pressure level of the speaker will change under different ambient temperatures. It is necessary to compensate the amplitude of the signal sent to the speaker according to the temperature. The steps are as follows:

[0091] (2.11) Place the standard microphone into the coupling cavity of the coupler, and then place the coupler into the ambient temperature box;

[0092] (2.12) The mobile phone sends calibration signals of n frequencies through the speaker, and receives the signals through the microphone and calculates the sound pressure level;

[0093] (2.13) Gradually adjust the temperature of the ambient temperature box from -10 degrees to 50 degrees, and record the sound pressure level measured by the microphone at each frequency every 5 degrees;

[0094] (2.13) Replace N speakers of the same model and record the difference between each frequency point at different temperatures and the corresponding frequency point at room temperature;

[0095] (2.14) After taking the average of N groups of data, a set of compensation values ​​for each frequency point at different temperatures is obtained;

[0096] (2.15) Let y = a1x 2 +a2x+a3 is the temperature and compensation value function at a frequency, where x is the temperature and y is the compensated sound pressure level. Use the least squares method to calculate a1, a2, and a3, and use this method to find the temperature compensation function of all frequency points; where a1x 2 is a1 times x squared, and a2x is a2 times x.

[0097] (2.16) During calibration, the mobile phone performs temperature compensation on each frequency point by substituting the measured temperature into the temperature compensation function of each frequency point.

[0098] Furthermore, when at different altitudes, different air pressures will cause the sound pressure levels emitted by the speaker to be different. The amplitude of the signal sent to the speaker needs to be compensated according to the air pressure. The steps are as follows:

[0099] (2.21) Place the standard microphone into the coupling cavity of the coupler, place the coupler into the air pressure box, and the mobile phone sends calibration signals of n frequencies through the speaker, while receiving the signals through the microphone and calculating the sound pressure level;

[0100] (2.22) Gradually adjust the air pressure in the pressure box from 50 kPa to 110 kPa, with each adjustment of 5 kPa, and record the sound pressure level measured by the microphone at each frequency;

[0101] (2.23) Replace N speakers of the same model and record the difference between each frequency point under different air pressures and the corresponding frequency point under standard atmospheric pressure;

[0102] (2.24) After taking the average of N groups of data, a set of compensation values ​​of each frequency point under different air pressures is obtained;

[0103] (2.25) Let y = a1x 2 +a2x+a3 is the air pressure and compensation value function at a frequency, x is the air pressure, y is the compensated sound pressure level, a1, a2, a3 are calculated using the least squares method, and the air pressure compensation function of all frequency points is calculated using this method;

[0104] (2.26) During calibration, the mobile phone achieves accurate air pressure compensation by substituting the measured air pressure value into the air pressure compensation function at each frequency point. When a mobile phone is equipped with a barometer, the mobile phone can directly measure the air pressure value through the barometer. A mobile phone without a barometer can obtain the current altitude H through GPS, obtain g through the mobile phone gravity accelerometer, substitute it into formula (3) to calculate the air pressure value at the current altitude, and then substitute the air pressure value into the air pressure compensation function at each frequency point to achieve accurate air pressure compensation;

[0105]

[0106] Among them, P is the air pressure, P0 is the standard atmospheric pressure, e is the natural constant, H is the altitude, g is the acceleration of gravity, M is the gas molecular weight 29, R is the constant 8.51, and T is the thermodynamic temperature.

[0107] After the above calibration compensations, the simple sound calibrator that costs only a few dozen yuan has the accuracy comparable to that of a professional sound calibrator.

[0108] The present invention and its embodiments are described schematically above, and the description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by it and designs a structural method and an embodiment similar to the technical solution without creativity without departing from the purpose of the invention, they shall all fall within the protection scope of the present invention.

Claims

1. A precision calibration method for a mobile phone-based acoustic calibration device, characterized in that: The sound calibration device comprises a mobile phone and a coupler, wherein a microphone, a speaker and a voltage display module connected to the speaker are arranged inside the coupler, an earphone is connected to the output end of the mobile phone, the earphone output pin is connected to the speaker, and the earphone input pin is connected to the microphone, and the accuracy calibration method specifically comprises the following steps: (1) Calibrate the frequency response of the speaker and microphone respectively; (2) The mobile phone performs temperature compensation on the speaker by calculating the temperature value; at the same time, the mobile phone performs air pressure compensation on the speaker by calculating the air pressure value; (3) The mobile phone generates sinusoidal signals of different frequencies using formula (1), and the sinusoidal signals are played through the calibrated speaker; Among them, x is the sinusoidal signal, A is the amplitude, ω is the angular frequency, and φ is the initial phase angle; (4) The microphone collects the feedback signal from the speaker and inputs it into the mobile phone. The mobile phone calculates the feedback signal into a sound pressure level. If the calculated sound pressure level is less than the target value, the A value in formula (1) is increased. Otherwise, the A value is decreased to ensure that the sound pressure level output by the speaker is the target value. (5) Calibrate the output voltage of different mobile phones based on the target sound pressure level of the speaker output; The specific operation of temperature compensation for the speaker in step (2) is as follows: (2.11) Place the standard microphone into the coupling cavity of the coupler, and then place the coupler into the ambient temperature box; (2.12) The mobile phone sends calibration signals of n frequencies through the speaker, and receives the signals through the microphone and calculates the sound pressure level; (2.13) Gradually adjust the temperature of the ambient temperature box, and record the sound pressure level measured by the microphone at each frequency during each adjustment; (2.13) Replace N speakers of the same model and record the difference between each frequency point at different temperatures and the corresponding frequency point at room temperature; (2.14) After taking the average of N groups of data, a set of compensation values ​​for each frequency point at different temperatures is obtained; (2.15) Let y = a1x 2 +a2x+a3 is the temperature and compensation value function at a frequency, where x is the temperature and y is the compensated sound pressure level. The least square method is used to calculate a1, a2, and a3. The temperature compensation function of all frequency points is obtained by this method. (2.16) During calibration, the mobile phone performs temperature compensation on each frequency point by substituting the measured temperature into the temperature compensation function of each frequency point; The specific operation of air pressure compensation for the speaker in step (2) is as follows: (2.21) Place the standard microphone into the coupling cavity of the coupler, place the coupler into the air pressure box, and the mobile phone sends calibration signals of n frequencies through the speaker, while receiving the signals through the microphone and calculating the sound pressure level; (2.22) Gradually adjust the air pressure in the air pressure box and record the sound pressure level measured by the microphone at each frequency after each adjustment; (2.23) Replace N speakers of the same model and record the difference between each frequency point under different air pressures and the corresponding frequency point under standard atmospheric pressure; (2.24) After taking the average of N groups of data, a set of compensation values ​​of each frequency point under different air pressures is obtained; (2.25) Let y = a1x 2 +a2x+a3 is the air pressure and compensation value function at a frequency, x is the air pressure, y is the compensated sound pressure level, a1, a2, a3 are calculated using the least squares method, and the air pressure compensation function of all frequency points is calculated using this method; (2.26) During calibration, the mobile phone achieves accurate air pressure compensation by substituting the measured air pressure value into the air pressure compensation function at each frequency point.

2. The accuracy calibration method of the sound calibration device based on a mobile phone according to claim 1, characterized in that: The step (5) of calibrating the output voltage of different mobile phones includes the following steps: (5.1) Place the standard microphone into the coupling cavity of the coupler at room temperature, and generate a standard calibration signal; (5.2) Adjust the signal amplitude generated by the mobile phone so that the sound level meter connected to the standard microphone displays the target value; (5.3) Check the voltage displayed by the voltage display module connected to the speaker, recorded as v volts; (5.4) Adjust the signal amplitude generated by different mobile phones so that the voltage display module of each mobile phone displays v volts, that is, the sound pressure level output by the speaker can reach the target value.

3. The accuracy calibration method of the sound calibration device based on a mobile phone according to claim 1, characterized in that: The calibration of the speaker and the microphone in step (1) is specifically as follows: (1.1) Speaker frequency response calibration (1.11) Place the standard microphone into the coupling cavity of the coupler at room temperature, and the mobile phone generates n calibration signals that need to be calibrated; (1.12) After the sound level meter connected to the standard microphone reads the sound pressure level of n calibration signals, it takes the critical sound pressure level as the reference and records the difference between the sound pressure level at each frequency point and the critical sound pressure level; (1.13) Replace N speakers of the same model, repeat step (1.12), and record the difference between the sound pressure level at each frequency point and the critical sound pressure level; (1.14) Take the average value of N groups of data and input it into the mobile phone as the frequency response compensation parameter of each frequency point of the speaker; (1.15) The mobile phone plays the calibration signal and adds different frequency signals to the frequency response compensation parameters of the corresponding frequencies to ensure that the signals of each calibration frequency emitted by the speaker are flat; (1.2) Microphone frequency response calibration (1.21) The mobile phone receives the calibration signal of each frequency through the microphone and calculates the sound pressure level. Formula (2) takes the critical sound pressure level as the benchmark and records the difference between the sound pressure level at each frequency point and the critical sound pressure level; (1.22) Replace N microphones of the same model, repeat step (1.21), and record the difference between the sound pressure level at each frequency point and the critical sound pressure level; (1.23) Take the average value of N groups of data and input it into the mobile phone as the frequency response compensation parameter of each frequency point of the microphone; (1.24) When the mobile phone measures the sound pressure level of the feedback signal through the microphone, the microphone frequency response compensation parameter is added so that the frequency response of each calibration frequency measured by the microphone is flat; Where L is the sound pressure level, Pa is the measured sound pressure, n is the number of sound pressures over a period of time, and P0 is the reference 0 dB.

4. The accuracy calibration method of the sound calibration device based on a mobile phone according to claim 1, characterized in that: In the step (2.16), a temperature sensor is provided inside the mobile phone, and the mobile phone measures the temperature value through the temperature sensor.

5. The accuracy calibration method of the sound calibration device based on a mobile phone according to claim 1, characterized in that: In the step (2.26), a barometer is provided inside the mobile phone, and the mobile phone measures the air pressure value through the barometer.

6. The accuracy calibration method of the sound calibration device based on a mobile phone according to claim 1, characterized in that: In the step (2.26), the mobile phone is provided with a positioning system, and the current altitude is obtained through the positioning system, and g is obtained through the gravity accelerometer of the mobile phone, and the air pressure value at the current altitude is calculated by substituting it into formula (3), and then the air pressure value is substituted into the air pressure compensation function of each frequency point to realize air pressure compensation; Among them, P is the air pressure, P0 is the standard atmospheric pressure, e is the natural constant, H is the altitude, g is the acceleration of gravity, M is the gas molecular weight 29, R is the constant 8.51, and T is the thermodynamic temperature.

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