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NVH Noise Test for Auto Parts
1、Overview
English abbreviation of Noise, Vibration, Harshness. This is a comprehensive question to measure the quality of car manufacturing. It gives the car the most direct feeling, which is the comfort and quietness of the ride.
Compared with traditional internal combustion engine-powered vehicles, the noise and vibration levels generated by the motors of new energy vehicles are much lower during operation, but at the same time, the noise and vibration generated by the original vehicle subsystems will also bring more obvious physical sensations, which is Just directly cause the ride comfort of car users to decline.
So in response to the above problems, we have a complete system from the software test algorithm to the hardware test equipment, which can quickly and accurately present the data of the NVH noise test items in a visualized way.
2、NVH noise application test
The research on the NVH characteristics of automobiles should take the whole vehicle as the research object, but because the automobile system is extremely complex, it is often decomposed into multiple systems for research, such as the power system (engine, motor, etc.), subsystems (electric rearview mirror , electric windows, HUD up display, steering wheel, etc.) etc.
2.1、NVH noise test configuration
ACC 1861 three-axis accelerometer features:
Multi-axial vibration signal acquisition, used in the research and development and application of vehicles and aviation
M663+A802 free-field microphone features:
Prepolarized free-field measurement microphone for measuring the undistorted real sound pressure before the microphone is placed in the sound field
PM 6682 audio analyzer features:
21V output, 100V input
Single-ended and differential support
Ultra-low noise, low distortion
MegaSig private drive, more stable test
PM 0083 signal conditioner:
4 Channel IEPE Exciter
3-channel power amplifier with a continuous power of 16w
AudioExpert audio analysis software features:
Complete Audio Analysis Algorithm Library
Supports automatic sequence editing
Support LabVIEW call
Support for remote control
2.2、NVH noise test item
1.Time-varying loudness test: According to the collected signal, calculate the curve of the product motor rotation loudness changing with time, and analyze the FFT diagram to obtain the following four values
Loudness Slope: The slope of the calculated curve from the beginning to the end
Loudness Intercept: The intersection of the curve with the loudness y-axis
Loudness average: average loudness of the entire curve
Loudness Maximum: The maximum loudness of the entire curve
2.Tremolo test: Calculate the corresponding tremolo signal according to the collected signal, analyze the FFT graph to get the following four values
Tremolo frequency: number of cycles per unit time
Max Percent Difference: Maximum relative amplitude change of tremolo
Maximum Loudness: The maximum value corresponding to the maximum relative amplitude change of the tremolo
Minimum Loudness: The minimum value corresponding to the maximum relative amplitude change of the tremolo
3. Characteristic loudness test: According to the collected signal, calculate the characteristic loudness curve of this section of signal, compare it with the set gold machine curve, and analyze the FFT graph to get the following three values
Relative pitch total excess value: the total area of the current curve exceeding the gold machine curve
Characteristic Loudness: The bark domain loudness calculated according to the characteristic loudness formula
Characteristic loudness level: the result calculated according to the loudness and loudness level formulas
4. Impulse loudness test: According to the collected signal, set the loudness start value and end value parameters, calculate the waveform that exists in this signal and within the set range, and analyze the FFT graph to obtain the following three values
Loudness Maximum: The maximum loudness of the entire curve
Duration*rms: area in the curve circle within the set range
Pulse duration: the duration of the signal within the set range
5. Maximum noise value test: at a fixed distance, the test value cannot exceed the prescribed db value
6. Order analysis: analyze the order spectrum under different rotational speeds
2.3、NVH noise test link
Automobile HUD head-up display, automobile electric rearview mirror, automobile electric window, automobile electric seat, automobile steering wheel and other subsystems: abnormal noise test
Automotive engine, automotive motor and other power systems: Abnormal sound test/vibration test
Take the car HUD head-up display NVH noise test link as an example for introduction:
After the product is reset, the MPA 663 free-field microphone starts to collect signals, and then the AudioExpert audio analysis software controls the rotation of the HUD display motor. The MPA 663 free-field microphone collects the complete signal of the HUD motor’s back and forth rotation, and then sends the collected signal back to AudioExpert through the PM 6682. Perform abnormal sound analysis.
Taking the automotive motor test link as an example: Abnormal sound test/vibration test
After the product is reset, the MPA 663 free-field microphone starts to collect acoustic signals/ACC 1861 three-axis accelerometer collects vibration signals, and then the AudioExpert audio analysis software controls the engine rotation, and the MPA 663 free-field microphone/ACC 1861 three-axis acceleration collects the complete signal of engine rotation. Then the collected signal is sent back to AudioExpert through PM 6682 for abnormal noise/vibration analysis.