UFSC apply LabVIEW and Ni Compactdaq to acoustic beam forming of vehicle passing noise test

Acoustic image recognition of tires and exhaust noise at 50 km/h, 1,904.3 Hz "We have chosen a compact, DC-powered NI hardware that provides power to the microphone in the array. -Samir N. Gerges, the University of Santa Catarina (UFSC)   Challenge: Develop a portable and affordable acoustic beamforming to identify noise sources through noise measurement and other applications.   Solution: Spiral array with 32 microphones, ni LabVIEW software, ni Sound and Vibration measurement kit, and 32-channel NI Compactdaq system, with 8 NI 9234 4 channel dynamic Signal Acquisition (DSA) Module to obtain the visual image of the noise source to identify the signal generated by the driving vehicle.     The noise and vibration Laboratory at the Federal University of San UFSC (Brazil) is engaged in a variety of project studies and is involved in the automotive industry to enable products to meet noise and vibration standards. In addition to supporting the development of the local industry, our school also vigorously promotes the academic development of undergraduate/postgraduate teaching and research. By standardizing the noise test, the maximum incidental noise level can be quantified during the operation of the vehicle. In many countries, government agencies have restrictions on sound testing, usually ISO362------measure the noise generated by the acceleration of road vehicles. These regulations are designed to record the main sources of noise generated by vehicles in urban traffic, usually at an speed limit of 50 or 70 km/h. Vehicle through noise testing can be verified that a standard car, the resulting traffic noise shall not exceed the prescribed limit. Many parts of the car produce noise, including motors, exhaust devices, transmissions and tyres. The standard noise test does not recognize the source noise that will cause the test to fail, so we need a technique to visualize the sound field to distinguish the different sound sources. In this test, we used beamforming to see which sound sources would significantly increase the overall noise and influence the vehicle through noise. Beamforming we have built a beam-forming device, or "acoustic camera", which is constructed of a 32-microphone spiral array with a maximum diameter distance of 1 meters between the microphones, which can be used to capture the visual image of the noise source, and we have also formed a 1.1*1-m metal mesh. The array is positioned in the same position as a single microphone in a standard test, 7.5 meters from the channel centerline, and a center distance of 1.3m from the ground, ensuring that all measurement conditions pass through the test. Our students use the Low-cost electret microphone to build the array microphone. Traditional directional array hardware is made up of capacitive microphones and preamplifier on the market, but too expensive for laboratory use. CreatedAn integral array microphone can save money and provide students with valuable projects. The NASA Langley Research Center found that the microphone frequency response produced by the Electret cartridge is suitable for the directional array, the amplitude and phase response of the audio spectrum is the smallest and the frequency changes moderate. We have completed the design based on the above research. Data acquisition We use NI USB-9162 High speed C Series USB outer box, with 8 ni 9234 DSA module for data collection. We chose a compact, DC-powered NI hardware that provides power to the microphone in the array. The module has no aliasing bandwidth up to kHz. In addition, the phase matching of the channel is very important for acoustic beamforming, and the system stipulates that the phase mismatch between any two channels can not exceed one degree. Because the system is DC power supply, so the use of battery operation is very convenient. Running LabVIEW software and sound and vibration measurement kits on laptops can easily convert voltage values into engineering units used in noise measurement. In addition, the Sound and vibration measurement kit conforms to the international standards of IEC61260 (electroacoustic, Octave and octave band-pass filters) and IEC61672 (electroacoustic and sound level meter) sound level measurement, weighted filter, and octave analysis, and its measurement results are accurate and repeatable. After analyzing the data acquisition, we use the traditional delay addition beamforming algorithm to analyze it. We summarize the sound signals and describe the different propagation paths from the source to the different microphones. The sound source is high speed through the acoustic camera (the speed of the modern vehicle is still slow compared with the sampling speed of the data acquisition system), which enables the beam to concentrate and track the sound source through the microphone array. We must calibrate the Doppler effect of the positive and negative Doppler process, which includes amplitude and frequency correction, thus obtaining coherent signal totals. In order to calibrate the acoustic measurement data and the vehicle photos and the stack noise amplitude being tested, we started the buzzer (the main part is about 90 decibels under 2.2 khz) and the vehicle running at a speed of 50 km/h, allowing it to pass through the array as conventionally tested. We use this method to replace the stability measurement, precisely because it collects fast and high quality. It also presents a similar recording in the measurement. The location of the buzzer allows accurate alignment of photos and data. Because of the noise caused by the movement of the tyres and the turbulence around the vehicle, we applied the technology to the vehicle and accurately assessed and identified the noise. In this case, we can do a good job of reducing the traffic noise outside the wind tunnel.