An experimental apparatus and method for measuring the full-angle frequency response characteristics of the nasal cone.

Abstract

This invention relates to the field of nasal cone frequency response characteristic testing technology, specifically to a testing device and method for measuring the full-angle frequency response characteristics of a nasal cone. The device includes: a microphone connected to the nasal cone under test for generating acoustic signals; a rotatable microphone bracket for mounting the microphone; a standard sound source for generating sound waves with preset frequencies and amplitudes; a standard sound source bracket for mounting the standard sound source; and a data acquisition system for acquiring the acoustic signals of the microphone corresponding to different rotation angles of the rotatable microphone bracket, generating noise curves of the nasal cone at all angles, and normalizing the noise curves to generate frequency response curves of the nasal cone at each angle. Based on the above testing device, the full-angle frequency response characteristics can be measured comprehensively and accurately, resulting in more accurate nasal cone acoustic characteristic test data to better meet specific usage requirements.

Description

Technical Field

[0001] This invention relates to the field of testing technology for the frequency response characteristics of the nasal cone, and specifically to a test apparatus and method for measuring the full-angle frequency response characteristics of the nasal cone. Background Technology

[0002] When aircraft or other objects undergo acoustic testing in an acoustic wind tunnel laboratory, the test section is located in an airflow area. To obtain accurate acoustic test data, nose cones are often installed on the microphones in the test section to reduce additional noise introduced by the airflow. Each nose cone has its own unique acoustic characteristics, which are related to wind speed, sound source frequency, and the orientation of the sound source relative to the nose cone. The sound source frequency and the orientation of the sound source relative to the nose cone represent the frequency response characteristics of the nose cone in different directions of sound wave entry. In related technologies, the acoustic characteristics of the nose cone only consider the relationship between the nose cone and wind speed, without considering the relationship between the sound source frequency and the orientation of the sound source relative to the nose cone, thus introducing errors into the test data and causing inaccurate test results.

[0003] The nose cone's streamlined, bullet-shaped tip is designed to minimize air resistance and disturbance. Installing this nose cone at the microphone tip can significantly reduce noise generated by airflow passing through the microphone by approximately 10 dB, effectively reducing the microphone's self-noise in high-speed airflow. Each nose cone has unique acoustic characteristics; even nose cones with the same structure will have different acoustic characteristics, which are related to wind speed, sound source frequency, and the orientation of the sound source relative to the nose cone. The relationship between acoustic characteristics and wind speed refers to the magnitude of the self-noise generated by the nose cone under different incoming wind speeds. In related technologies, microphones with nose cones are placed in the main airflow area in an acoustic wind tunnel laboratory, and the noise spectrum of the microphone is measured under different incoming wind speeds, thus obtaining the self-noise generated by the nose cone under different incoming wind speeds. The relationship between acoustic characteristics and sound source frequency refers to the frequency response characteristics of the nose cone; the relationship between acoustic characteristics and sound source orientation refers to the directivity of the nose cone.

[0004] In related technologies, the acoustic characteristics of the nose cone only consider the self-noise of the nose cone, while ignoring the frequency response characteristics and directivity of the nose cone, resulting in low accuracy of test results, and even completely wrong test results in certain sound incident angles and noise frequency bands. Summary of the Invention

[0005] In view of this, the present invention provides a test apparatus and method for measuring the full-angle frequency response characteristics of the nasal cone, so as to solve the problem that the nasal cone acoustic characteristic test data are inaccurate because the relationship between the sound source frequency and the position of the sound source and the nasal cone is not considered.

[0006] In a first aspect, the present invention provides a test apparatus for measuring the full-angle frequency response characteristics of the nasal cone, comprising:

[0007] A microphone, connected to the nose cone under test, is used to generate acoustic signals;

[0008] Rotatable microphone stand for mounting microphones;

[0009] A standard sound source is set at a preset distance directly in front of the microphone to generate sound waves with preset frequencies and amplitudes.

[0010] Standard sound source bracket for mounting a standard sound source;

[0011] The data acquisition system is used to collect the acoustic signals of the microphone corresponding to different rotation angles of the rotatable microphone bracket, generate the noise curve of the nose cone at all angles, and normalize the noise curve to generate the frequency response curve of the nose cone at each angle.

[0012] Beneficial effects: This invention provides a test device for measuring the full-angle frequency response characteristics of a nose cone. The rotatable microphone bracket allows for flexible adjustment at different angles. Combined with a data acquisition system to collect acoustic signals from the microphone at various angles, the frequency response characteristics of the nose cone across the entire angle range can be obtained comprehensively and accurately. This helps to understand in detail the specific response of the nose cone to sound waves in various directions, providing accurate angle-dependent data for subsequent related research and design optimization. Configuring a standard sound source and setting it at a preset distance directly in front of the microphone ensures that the generated sound waves have stable and known frequency parameters. Using this as a reference, the input of sound waves during the measurement process is standardized and traceable, thereby improving the accuracy and reliability of the overall measurement results and facilitating comparative analysis between different measurements and different test devices. The data acquisition system can not only collect acoustic signals to generate noise curves, but also perform further normalization processing to obtain frequency response curves at various angles. Based on the comprehensive and accurate measurement of the full-angle frequency response characteristics by the aforementioned test device, the obtained acoustic characteristic test data of the nose cone is more accurate. Designers can clearly understand the advantages and disadvantages of the acoustic performance of the nose cone at different angles, and then make targeted optimizations and adjustments to the structure and materials of the nose cone. Based on the acoustic characteristic test results of the nose cone, a nose cone that meets the requirements of the acoustic wind tunnel test is selected. At the same time, the acoustic wind tunnel test results are corrected based on the acoustic characteristic test results of the nose cone to obtain accurate test data to better meet specific application needs.

[0013] In one alternative implementation, the distance between the standard sound source and the microphone is not less than the wavelength of the standard sound source sound wave by a preset multiple.

[0014] Beneficial effects: When the sound source and microphone are close together, a near-field effect will occur. When the distance between the standard sound source and the microphone is not less than the wavelength of the standard sound source's sound wave by a preset multiple, the microphone's position is closer to the far-field condition. This can avoid the interference of the complex relationship between sound pressure and particle velocity caused by the near-field effect, making the measured acoustic signal more consistent with the simple and stable propagation law in the far field. Under the same experimental conditions, the signal obtained from each measurement has high stability and repeatability, thereby improving the accuracy of the measurement.

[0015] In one alternative implementation, both the rotatable microphone bracket and the standard sound source bracket are covered with a noise reduction device.

[0016] Beneficial effects: Both the rotatable microphone bracket and the standard sound source bracket are covered with a noise reduction device, which can reduce the interference of the bracket on the sound field, optimize the measurement environment, and reduce the impact of background noise, thereby improving the accuracy and reliability of the measurement.

[0017] Secondly, based on the aforementioned test apparatus, the present invention provides a test method for measuring the full-angle frequency response characteristics of the nasal cone, comprising:

[0018] The microphone with the nose cone attached is fixed to the rotatable microphone bracket.

[0019] Adjust the sound frequency and amplitude of the standard sound source according to the preset sound frequency and preset sound amplitude, and after stabilization, use the data acquisition system to continuously acquire the acoustic signal of the microphone.

[0020] Rotate the rotatable microphone bracket base to one full turn by rotating it at a preset constant angle, and continuously collect the microphone sound signals at different angles using the data acquisition system.

[0021] Adjust the sound wave frequency of the standard sound source, rotate the rotatable microphone bracket base to one full turn at a preset constant angle, and continuously collect the microphone acoustic signals at different angles using the data acquisition system.

[0022] Based on the data acquisition system, microphone sound signals at different frequencies and angles are collected to generate noise curves at all angles of the nose cone. The noise curves are then normalized to generate frequency response curves of the nose cone at various angles.

[0023] Beneficial Effects: Based on the aforementioned experimental apparatus, this invention provides a test method for measuring the full-angle frequency response characteristics of a nose cone. By placing the nose cone on a microphone and rotating the microphone support base one revolution, acoustic signals of the nose cone across the entire angular range can be acquired. By adjusting the frequency and amplitude of the sound wave from a standard sound source and continuously acquiring the microphone's acoustic signals using a data acquisition system, the relationship between the acoustic characteristics of the nose cone and the sound source's orientation and the frequency and amplitude of the standard sound source can be obtained. This generates noise curves for the nose cone across the entire angular range, and normalizes these noise curves to generate frequency response curves for the nose cone at various angles. Through comprehensive and accurate measurement of the full-angle frequency response characteristics, designers can clearly understand the strengths and weaknesses of the nose cone's acoustic performance at different angles, and then make targeted optimizations and adjustments to the nose cone's structure and materials. Based on the nose cone acoustic characteristic test results, a nose cone that meets the requirements of acoustic wind tunnel testing can be selected. Simultaneously, the acoustic wind tunnel test results can be corrected based on the nose cone acoustic characteristic test results to obtain accurate test data to better meet specific application needs.

[0024] In one alternative implementation, the sound wave frequency of the standard sound source is a preset octave band center frequency of (1-20K)Hz.

[0025] Beneficial effects: The standard sound source frequency is selected with a preset octave band center frequency of (1-20K)Hz. The preset octave band (i.e., the frequency range of each band is a preset multiple of the center frequency) can provide fine frequency division, which can more effectively improve the accuracy of measurement and the convenience of analysis when performing precise acoustic measurements.

[0026] In one optional implementation, the rotatable microphone bracket base is rotated one full turn at a preset constant angle, and the microphone sound signals at different angles are continuously acquired using a data acquisition system, including:

[0027] The microphone bracket base can be rotated clockwise / counterclockwise to a preset constant angle to complete one full turn. Each time the base is rotated, the data acquisition system continuously collects the microphone's sound signal to obtain the noise curve of the nose cone of the standard sound source at the incident wave angle corresponding to the preset sound wave frequency and preset magnitude.

[0028] Beneficial effects: By rotating at a constant angle, the microphone can be ensured to collect sound from different directions evenly on a complete circle, resulting in more comprehensive and uniform sound data, thereby improving the representativeness and accuracy of the test results.

[0029] In one optional implementation, the noise curve is normalized, including:

[0030] The sound pressure level measured at the preset frequency is used as the reference value. The ratio of the amplitude of the sound pressure level measured at other frequencies on the noise curve to the sound pressure level measured at the preset frequency is used as the normalized value for other frequencies.

[0031] Beneficial effects: In unnormalized noise curves, the absolute value of sound pressure level is affected by a variety of factors. Normalization can eliminate the influence of different dimensions and enhance numerical stability. Therefore, the normalized curve can more clearly show the changing trend of the nose cone frequency response characteristics.

[0032] In one alternative implementation, the preset sound wave size does not exceed the microphone's range.

[0033] Beneficial effects: The range of a microphone refers to the maximum range of sound pressure levels it can accurately capture and convert. If the size of the sound wave exceeds the microphone's range, it may cause signal distortion or nonlinear response. Distortion will affect the accuracy of the measurement results and will not be able to truly reflect the characteristics of the sound field. Ensuring that the size of the sound wave does not exceed the range helps the microphone operate within its linear operating range and maintains the authenticity of the acoustic signal.

[0034] In one alternative implementation, the test for measuring the full-angle frequency response characteristics of the nose cone is conducted in an anechoic chamber.

[0035] Beneficial effects: The anechoic chamber provides a low-noise, reflection-free, and environmentally stable testing environment, which helps to eliminate interference from external noise and reflections, thereby improving the accuracy, reliability, and stability of the test. Attached Figure Description

[0036] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0037] Figure 1 A test apparatus for measuring the full-angle frequency response characteristics of the nasal cone;

[0038] Figure 2 This is a schematic diagram of the nasal cone.

[0039] Figure 3 This is a schematic diagram of a microphone;

[0040] Figure 4 A schematic diagram of a microphone with a nose cone installed;

[0041] Figure 5 This is a schematic diagram of a rotatable bracket;

[0042] Figure 6 The experimental procedure for measuring the full-angle frequency response characteristics of the nasal cone;

[0043] Figure 7 The noise curve is a typical 1 / 3 octave band noise curve for the full angle of the nose cone;

[0044] Figure 8 The frequency response curve under a single preset angle;

[0045] Figure 9 It is the center of 1 / 3 octave band.

[0046] Explanation of reference numerals in the attached figures:

[0047] 1. Microphone; 2. Rotatable microphone bracket; 201. Microphone mounting rod; 202. Bracket rotation limiting mechanism; 203. Bearing; 204. Mounting support; 205. Scaled chassis; 3. Standard sound source; 4. Standard sound source bracket; 5. Data acquisition system. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, 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.

[0049] The full-angle frequency response of the nose cone refers to how to measure and analyze the frequency response of sound at different angles in acoustic research. The frequency response characteristics of the nose cone determine its sound response characteristics at different frequencies and in different directions. Understanding its full-angle frequency response characteristics is crucial for improving sound propagation, design optimization, and enhancing equipment performance.

[0050] This invention provides a test apparatus for measuring the full-angle frequency response characteristics of a nose cone. A microphone is connected to the nose cone under test, simulating the microphone's operation in a high-speed flowing gas environment while fixing the nose cone. A standard sound source is used to generate sound waves of preset frequencies and amplitudes to measure the microphone's acoustic signals at different sound source frequencies. A preset distance is placed directly in front of the microphone to ensure the standard sound source can be considered a point source. A standard sound source support is used to fix the standard sound source and provide structural support. A data acquisition system is used to collect the microphone's acoustic signals and simultaneously generate a noise curve and a frequency response curve of the nose cone at various angles generated by normalizing the noise curve.

[0051] The following is combined with Figures 1 to 9 The following describes embodiments of the present invention.

[0052] According to an embodiment of the present invention, in a first aspect, a test apparatus for measuring the full-angle frequency response characteristics of the nasal cone is provided, such as... Figure 1 As shown, it includes:

[0053] Microphone 1, connected to the nose cone under test, is used to generate acoustic signals. The main function of microphone 1 is to convert acoustic signals into electrical signals. Through its internal structure, it converts the mechanical vibrations of sound waves into corresponding electrical signals, thereby achieving sound capture and transmission. The nose cone, for example... Figure 2 As shown, the microphone is as follows Figure 3 As shown, a microphone connected to a nose cone... Figure 4 As shown.

[0054] The rotatable microphone bracket 2 is used to mount the microphone 1; the rotatable microphone bracket 2 in this embodiment of the invention is as follows: Figure 5 As shown, the device includes: a microphone mounting rod 201, a support rotation limiting mechanism 202, a bearing 203, a mounting column 204, and a graduated chassis 205. The bearing 203 is located at one end of the mounting column 204, and the microphone mounting rod 201 is located at the other end of the mounting column 204. The support rotation limiting mechanism 202 is connected to the bearing 203. The graduated chassis 205 is detachable. When the rotation angles of two adjacent tests are inconsistent or when measuring the frequency response characteristics of a single special angle, such as the required angles of 45° and 30° for two adjacent tests or a single required rotation angle of 37°, only the graduated chassis 205 needs to be replaced, which can improve the convenience and speed of the test device. In one implementation, the graduated chassis 205 and the bearing 203 are an integrated structure; in another implementation, the graduated chassis 205 and the bearing 203 are separate parts that are installed together. Generally, the microphone mounting rod 201, the bracket rotation limiting mechanism 202, and the mounting column 204 are an integrated structure.

[0055] The rotatable microphone stand 2 allows for easy adjustment of the angle of the microphone 1, enabling the acquisition of sound waves at different directions and angles. This is crucial for capturing the omnidirectional sound field distribution of the sound source. The rotatable microphone stand 2 offers flexibility, allowing for convenient adjustment of the angle and position of the microphone 1 as needed. For different experimental requirements, researchers can quickly adjust the equipment configuration to perform sound field measurements at different directions and distances.

[0056] A standard sound source 3 is set at a preset distance directly in front of the microphone 1 to generate sound waves with preset frequencies and amplitudes. The standard sound source 3 provides a stable and known reference signal, ensuring the accuracy, standardization and comparability of acoustic measurements. In this embodiment of the invention, the frequency of the standard sound source 3 is adjusted by adjusting the voltage of the signal generator in the standard sound source 3 and by combining it with a power amplifier.

[0057] The standard sound source bracket 4 is used to mount the standard sound source 3. The standard sound source bracket 4 ensures that the standard sound source 3 maintains stable, safe and effective operation during measurement or experimentation, while effectively reducing the impact of external vibration on the standard sound source 3.

[0058] The data acquisition system 5 is used to acquire the acoustic signals of the microphone 1 corresponding to different rotation angles of the rotatable microphone bracket 2, generate the noise curve under the full angle of the nose cone, and normalize the noise curve to generate the frequency response curve of the nose cone at each angle.

[0059] A data acquisition system is a system that converts physical signals into digital signals and processes them, providing efficient and accurate real-time data acquisition and processing capabilities. The continuous acquisition time of a microphone's sound signal by the data acquisition system should be no less than 10 seconds. The microphone, as a sound signal capture device, connects its output to the input of the data acquisition system, typically via a cable or other physical connection, transmitting the electrical signal converted from the sound signal to the data acquisition system. For example, in a common condenser microphone, it converts changes in sound pressure into changes in capacitance, thereby generating a changing voltage signal. This voltage signal is then transmitted to the data acquisition system via wires for further processing. During operation, the data acquisition system may generate electromagnetic interference. If this interference is too close to the microphone, it may affect the microphone's ability to capture and convert sound signals. Therefore, in terms of layout, the data acquisition system is usually placed at a certain distance from the microphone, and electromagnetic shielding measures may be taken to reduce interference.

[0060] The experimental apparatus provided in this invention allows for flexible adjustment of the microphone bracket at different angles. Combined with a data acquisition system that collects acoustic signals from the microphone at various angles, it can comprehensively and accurately acquire the frequency response characteristics of the nose cone across the entire angular range. This helps to understand the specific response of the nose cone to sound waves in various directions, providing accurate angle-dependent data for subsequent research and design optimization. Configuring a standard sound source and placing it at a preset distance directly in front of the microphone ensures that the generated sound waves have stable and known frequency parameters, making the sound wave input during measurement standardized and traceable. This improves the accuracy and reliability of the overall measurement results and facilitates comparative analysis between different measurements and different experimental apparatuses. The data acquisition system not only collects acoustic signals to generate noise curves but also performs further normalization processing to obtain frequency response curves at various angles. Based on the comprehensive and accurate measurement of the full-angle frequency response characteristics obtained by the above-mentioned experimental apparatus, the experimental data on the acoustic characteristics of the nose cone are more accurate. Designers can clearly understand the advantages and disadvantages of the nose cone's acoustic performance at different angles and then make targeted optimizations and adjustments to the nose cone's structure and materials to better meet specific usage requirements.

[0061] In some embodiments, the distance between the standard sound source 3 and the microphone 1 is not less than the wavelength of the sound wave of the standard sound source 3 by a preset multiple.

[0062] In acoustic measurements, a near-field effect occurs when the sound source and microphone are close together. The near field refers to the region very close to the sound source. In this region, the relationship between sound pressure and particle velocity is complex and does not conform to the simple acoustic theory applicable in the far field. For example, for a simple point sound source, sound pressure is inversely proportional to distance in the far field, but this relationship does not hold true in the near field. Generally, the distance between the standard sound source 3 and the microphone 1 is not less than a multiple of the wavelength of the maximum preset sound wave of the standard sound source 3 (i.e., the wavelength corresponding to the lowest frequency). In this embodiment, the distance between the standard sound source 3 and the microphone 1 is not less than 2-3 wavelengths of the sound wave from the standard sound source 3. This avoids interference from the complex relationship between sound pressure and particle velocity caused by the near-field effect, making the measured acoustic signal more consistent with the simple and stable propagation laws in the far field. Under the same experimental conditions, the signal obtained from each measurement has high stability and repeatability, thereby improving the accuracy of the measurement.

[0063] In some embodiments, both the rotatable microphone bracket 2 and the standard sound source bracket 4 are covered with a noise reduction device.

[0064] The rotatable microphone bracket 2 and the standard sound source bracket 4 may generate certain mechanical noise or vibration during operation. These interferences may affect the measurement accuracy of the microphone 1 or the signal quality of the standard sound source 3. By installing a noise reduction device on the bracket, these unnecessary noise sources can be effectively isolated, and the reflection of sound waves can be effectively reduced, making the sound field more uniform and improving the accuracy of the signal received by the microphone. The noise reduction device is usually made of vibration-absorbing material, which can reduce the vibration of the bracket and the equipment itself and prevent these vibrations from being transmitted to the microphone 1 or the standard sound source 3, thereby affecting the accuracy of the measurement data. In this embodiment, the noise reduction device is sound-absorbing cotton, which is only an example and is not limited thereto.

[0065] Secondly, the present invention provides a test method for measuring the full-angle frequency response characteristics of the nasal cone, such as... Figure 6 As shown, it includes:

[0066] S1, fix the microphone with the nose cone attached to the rotatable microphone bracket.

[0067] In this embodiment of the invention, the rotatable microphone bracket 2 enables the microphone 1 to be precisely positioned and adjusted at different angles and directions, suitable for omnidirectional sound wave acquisition. The rotatable design means that the measurement personnel can quickly adjust the position and direction of the microphone 1 for rapid measurement or experimental setup, reducing the time and complexity of manual intervention. Combining the nose cone with the rotatable microphone bracket 2 ensures that the microphone 1 is accurately pointed to the standard sound source 3, thereby minimizing deviations or errors during the measurement process and avoiding stray sounds or noise from other directions, ensuring the clarity and accuracy of the signal. The fixed nose cone ensures that the sound waves received by the microphone 1 are consistent each time, avoiding differences caused by changes in the position or angle of the microphone 1. By using a stable rotatable bracket, the nose cone can always be maintained in the required position, reducing measurement deviations caused by inaccurate positioning, thereby improving the reliability of the test results.

[0068] S2, adjust the sound frequency and amplitude of the standard sound source according to the preset sound frequency and preset sound amplitude, and after stabilization, use the data acquisition system to continuously acquire the acoustic signal of the microphone.

[0069] In this embodiment of the invention, the standard sound source is adjusted according to the preset sound wave frequency and amplitude to ensure that the sound wave input in each experiment is stable and controllable. By adjusting the sound wave frequency and amplitude of the standard sound source 3, and after it stabilizes, the acoustic signal of the microphone is continuously acquired using a data acquisition system, which can effectively perform acoustic testing. Adjusting the sound wave frequency and amplitude of the standard sound source ensures that the output signal of the standard sound source is stable. The data acquisition system is used to continuously acquire signals and store data in real time to ensure the accuracy of the test and the availability of the data.

[0070] S3, rotate the rotatable microphone bracket base to one full turn at a preset constant angle, and continuously collect microphone sound signals at different angles using the data acquisition system;

[0071] This invention, by rotating the microphone bracket base one full turn, can completely cover all angles around the nose cone, allowing for the acquisition of the nose cone's response to sound waves in all directions within a 360° range. By continuously acquiring sound signals from different angles using a data acquisition system, the dynamic response of the nose cone during angle changes can be captured. In real-world environments, the acoustic environment faced by the nose cone is dynamically changing. For example, the angle of a car's nose cone changes as it turns, and the direction of surrounding noise sources also changes. In the aerospace field, the nose cone of an aircraft is subjected to aerodynamic noise, engine noise, and other sources from different directions during flight. This full-angle measurement can simulate various possible flight conditions, providing comprehensive data support for analyzing the acoustic performance of the nose cone under different flight attitudes.

[0072] S4, adjust the sound wave frequency of the standard sound source, rotate the rotatable microphone bracket base to one full turn at the preset constant angle again, and use the data acquisition system to continuously collect the microphone acoustic signals at different angles.

[0073] The rotatable microphone bracket 2 adjusts the direction of the sound source. By adjusting the sound frequency and amplitude of the standard sound source 3, the acoustic signal of the microphone is continuously acquired using a data acquisition system. This allows the acoustic signal of the nose cone at different frequencies and all angles to be obtained. The relationship between the acoustic characteristics of the nose cone and the direction of the sound source and the sound frequency and amplitude of the standard sound source 3 can be obtained, which helps to accurately locate the acoustic performance characteristics of the nose cone under different frequency-angle combinations.

[0074] S5, based on the data acquisition system, collects microphone sound signals at different frequencies and angles, generates noise curves at all angles of the nose cone, and normalizes the noise curves to generate frequency response curves of the nose cone at various angles.

[0075] The experimental method provided in this invention, by placing a nose cone on a microphone and rotating the microphone support base one revolution, can acquire the acoustic signal of the nose cone across the entire angular range. Furthermore, it takes into account different sound wave frequencies, thus providing a detailed description of the acoustic response of the nose cone at various frequencies and across the entire angular range, thereby improving the accuracy of the experimental data.

[0076] like Figure 7 The diagram shows the noise curves at the full angle of the nose cone when the frequency and amplitude of the sound wave from the standard sound source 3 are a single, specific value; when the positions of the microphone 1 and the standard sound source 3 are fixed, the frequency response curves corresponding to different frequencies and amplitudes of the sound wave from the standard sound source 3 are shown below. Figure 8 As shown.

[0077] In some embodiments, the sound wave frequency of the standard sound source is a preset octave band center frequency of (1-20K)Hz.

[0078] In this embodiment, as Figure 9 As shown, the standard sound source 3 frequency is selected from the center frequency of 1 / 3 octave band (1-20K) Hz for testing. The higher the accuracy of the nose cone frequency response curve, the smaller the octave band. For example, the center frequency of 1 / 6 octave band, 1 / 12 octave band or 1 / 24 octave band can be selected. The standard sound source frequency is selected from the center frequency of 1 / 3 octave band (1-20K) Hz. 1 / 3 octave band (that is, the frequency range of each band is 1 / 3 of the center frequency) can provide a finer frequency division. For precise acoustic measurements, it can more effectively improve the accuracy of measurement and the convenience of analysis.

[0079] In some embodiments, rotating the rotatable microphone bracket base to one full revolution at a preset constant angle, and continuously acquiring microphone sound signals at different angles using a data acquisition system, includes:

[0080] The microphone bracket base can be rotated clockwise / counterclockwise to a preset constant angle to complete one full turn. Each time the base is rotated, the data acquisition system continuously collects the microphone's sound signal to obtain the noise curve of the nose cone of the standard sound source at the incident wave angle corresponding to the preset sound wave frequency and preset magnitude.

[0081] In this embodiment, the preset constant angle is 30°. The finer the noise curve of the nose cone, the smaller the rotation angle of the support base. The rotation angle of the support base can be selected to be a smaller angle (should be a multiple of 360°), such as 15°. By rotating at a constant angle, it can be ensured that the microphone 1 collects sound from different directions evenly on a complete circle, so as to obtain more comprehensive and uniform sound data, thereby improving the representativeness and accuracy of the test results.

[0082] In some embodiments, normalizing the noise curve includes:

[0083] The sound pressure level measured at the preset frequency is used as the reference value. The ratio of the amplitude of the sound pressure level measured at other frequencies on the noise curve to the sound pressure level measured at the preset frequency is used as the normalized value for other frequencies.

[0084] During the measurement process, due to factors such as the intensity of the sound source and the measurement environment, the absolute values ​​of sound pressure measured at different frequencies may vary greatly. Normalization can eliminate this difference and unify different noise curves into a common standard range, thereby enabling direct comparison and analysis between different noise curves. Normalization can eliminate the influence of different dimensions and enhance numerical stability. Therefore, the normalized frequency response curve can more clearly show the trend of the nose cone frequency response characteristics with frequency. Unnormalized noise curves may mask the true changes in frequency response characteristics due to fluctuations in absolute sound pressure values.

[0085] In some embodiments, the preset sound wave magnitude does not exceed the microphone's range.

[0086] The range of microphone 1 refers to the maximum range of sound pressure levels it can accurately capture and convert. If the size of the sound wave exceeds the range of microphone 1, it may cause signal distortion or nonlinear response. Distortion will affect the accuracy of the measurement results and fail to truly reflect the characteristics of the sound field. Ensuring that the size of the sound wave does not exceed the range helps the microphone operate within its linear operating range and maintain the authenticity of the acoustic signal. Within the range, there is a clear linear relationship between the output of microphone 1 and the intensity of the sound wave. If the sound wave exceeds this range, the response of microphone 1 may become nonlinear, leading to measurement errors. Ensuring that the sound wave does not exceed the range of microphone 1 ensures that the relationship between its output and the intensity of the sound wave is accurate and improves measurement precision.

[0087] In some embodiments, the test for measuring the full-angle frequency response characteristics of the nasal cone is conducted in an anechoic chamber.

[0088] In a normal environment, sound waves are reflected by walls, the ground, and other objects, resulting in sound interference and complex reflection patterns. These reflected sounds can affect the accurate measurement of frequency response characteristics. In an anechoic chamber, due to its special design (such as sound-absorbing materials and structure), the reflection of sound waves is greatly reduced, and the sound field tends to be uniform, thus obtaining more realistic measurement results. An anechoic chamber provides a low-noise, reflection-free, and environmentally stable testing environment, which helps to eliminate interference from external noise and reflections, thereby improving the accuracy, reliability, and stability of the test.

[0089] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Although embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and all such modifications and variations fall within the scope defined by the present invention.

Claims

1. A test apparatus for measuring the full-angle frequency response characteristics of the nasal cone, characterized in that, include: A microphone, connected to the nose cone under test, is used to generate acoustic signals; A rotatable microphone bracket for mounting the microphone; A standard sound source is set at a preset distance directly in front of the microphone to generate sound waves with preset frequencies and amplitudes. A standard sound source bracket is used to mount the standard sound source. The data acquisition system is used to collect the acoustic signals of the microphone corresponding to different rotation angles of the rotatable microphone bracket, generate noise curves at all angles of the nose cone, and normalize the noise curves to generate frequency response curves of the nose cone at each angle.

2. The apparatus according to claim 1, characterized in that, The distance between the standard sound source and the microphone is not less than the wavelength of the standard sound source sound wave by a preset multiple.

3. The apparatus according to claim 1, characterized in that, Both the rotatable microphone bracket and the standard sound source bracket are covered with a noise reduction device.

4. A test method for measuring the full-angle frequency response characteristics of the nasal cone, based on the test apparatus according to any one of claims 1-3, characterized in that, include: The microphone with the nose cone attached is fixed to the rotatable microphone bracket. Adjust the sound frequency and amplitude of the standard sound source according to the preset sound frequency and preset sound amplitude, and after stabilization, use the data acquisition system to continuously acquire the acoustic signal of the microphone. Rotate the rotatable microphone bracket base to one full turn at a preset constant angle, and continuously collect microphone sound signals at different angles using a data acquisition system. Adjust the sound wave frequency of the standard sound source, rotate the rotatable microphone bracket base to one full turn at a preset constant angle, and continuously collect the microphone acoustic signals at different angles using the data acquisition system. Based on the data acquisition system, microphone sound signals at different frequencies and angles are collected to generate noise curves at all angles of the nose cone. The noise curves are then normalized to generate frequency response curves of the nose cone at various angles.

5. The test method for measuring the full-angle frequency response characteristics of the nasal cone according to claim 4, characterized in that, The sound wave frequency of the standard sound source is the preset octave band center frequency of (1-20K)Hz.

6. The test method for measuring the full-angle frequency response characteristics of the nasal cone according to claim 4, characterized in that, The process of rotating the rotatable microphone bracket base to one full revolution at a preset constant angle, and continuously acquiring microphone sound signals at different angles using a data acquisition system, includes: The rotatable microphone support base is rotated clockwise and counterclockwise by a preset constant angle to complete one revolution. Each time the base is rotated by an angle, the data acquisition system continuously collects the microphone sound signal to obtain the noise curve of the nose cone of the standard sound source at the incident wave angle corresponding to the preset sound wave frequency and preset magnitude.

7. The test method for measuring the full-angle frequency response characteristics of the nasal cone according to claim 4, characterized in that, The normalization process for the noise curve includes: The sound pressure level measured at a preset frequency is used as the reference value. The ratio of the amplitude of the sound pressure level measured at other frequencies on the noise curve to the sound pressure level measured at the preset frequency is used as the normalized value for other frequencies.

8. The test method for measuring the full-angle frequency response characteristics of the nasal cone according to claim 4, characterized in that, The preset sound wave size does not exceed the range of the microphone.

9. The test method for measuring the full-angle frequency response characteristics of the nasal cone according to any one of claims 4 to 8, characterized in that, The test used to measure the full-angle frequency response characteristics of the nasal cone was conducted in an anechoic chamber.

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