Sound Intensity Analysis System Based On Virtual Instrument

Sound intensity is the sound wave intensity in sound field, which equals sound energy through the unit area perpendicular to the energy flow direction. Since the sound intensity is a vector in nature, which has the priority to sound pressure when used to describe sound field. Sound intensity measurement is free from environmental influence and belongs to don't get in touch measurement, it is also free from the restriction of the type of noise, therefore, Sound intensity measurement has already become an important means of the noise measurement.This paper introduces sound intensity and its scaling method and the theorem of two-microphone sound intensity. The theoretical, manufacture and random errors of the two-microphone sound intensity measurement is analyzed in details, the measurement reduction method is also introduced in this paper. The error of the two-microphone sound intensity measurement system is deduced according to the transfer function, and the sound intensity measurement system is also corrected.Virtual Instrumentation is becoming a popular tool in measurement, test and automation as a result of rapid development of computer technology. With the virtual instrument technology, we only have to send the signals to be tested into computers via I/O interface devices, and then with special VI developing tools and the abilities of data analyzing,data processing and data storing of computers we can easily design a VI system with meets special testing requests. This paper mainly makes use of a virtual instrument technique to develop a kind of sound intensity analysis system that structure is simple and easily to use.The sound intensity analysis system studied by this paper uses sound pressure for the main test signal, adopts two-microphone sound intensity method to sound measurement, and the measurement don't easily be subjected to environmental influence. The hardware includes B&K microphone 4165, preamplifier 2169, double-channel power supply 2807, NI PCI6024E DAQ card and PC. The part of software includes the data acquisition module, the data analysis module, systematic marked module. The systematic marked module can correct the system error and lower the matching request of the microphones and other hardware. The data analysis module includes the 1/3 times frequency distances, A accounting power correction functions. This system is developed with the graphical virtual instruments programming tool LabVIEW7.0, which is produced by NI. With this developing environment, all the hardware is integrated into a well functioning test system.In the end of this paper, by carrying on a contrast experiment between this system and B&K pulse 2000 auto motion noise system, we can prove that the error margin of this system is smaller, can satisfy the sound intensity measurement of general accuracy.