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Research On The Wind Speed Testing Algorithm Based On Acoustic Parametric Array

Posted on:2017-03-09Degree:MasterType:Thesis
Country:ChinaCandidate:X M LiFull Text:PDF
GTID:2180330485488047Subject:Electronic and communication engineering
Abstract/Summary:PDF Full Text Request
The traditional method of measuring wind speed is ultrasonic, which has limitation on measuring average wind speed of a wide space, due to its frequency is too high to propagate long distance in the air. Common audible sound doesn’t have directivity characteristic, and sound field has no distribution rule, resulting in impossibly used in measuring wind speed. So this paper proposes using the acoustic parametric array to measure average wind speed of a wide space. Acoustic parametric array can generate a difference frequency audible sound with strong directivity, whose frequency is lower than the ultrasonic and propagation distance is longer, distribution of the sound field is clearer, all of these advantages can be used to solve measuring problem. In this paper, the core work is taking advantage of wind speed influencing the sound field distribution of acoustic parametric array to do research on the wind speed testing algorithm based on acoustic parametric array.Firstly, the basic theory of acoustic parametric array is introduced, and several basic testing characteristic is also analyzed by theory and simulation, including the character of directivity, beam distribution feature, and the nonlinear characteristic of sound pressure level(SPL) form, which provides feasibility basis for the use of acoustic parametric array to measure wind speed. For studying the relationship between the sound field of acoustic parametric array and different wind speed, in this paper, starting from basic sound wave(including plane wave and spherical wave), introducing the factor of wind speed into acoustic wave equation and motion equation, it is concluded that wind speed does not affect size of acoustic pressure, but will affect the acoustic propagation direction, relying on this conclusion draw an inference-the sound field distribution of acoustic parametric array will shift due to vertical wind action.Secondly, for studying acoustic parametric array acoustic field’s and wind field’s distribution and characteristics, we do a research on the related theory by simulation. To build a model of acoustic parametric array sound field, by simulating KZK equation to obtain acoustic parametric array sound field distribution, and found out distribution curves is first increasing then decrease, by comparing with ultrasonic sound field, the characteristic of parametric array acoustic field is more obviously. For wind field model, do not consider wind direction, this paper build the two-dimensional wind field model based on the theory of combination and the simulation analysis, and found that different wind speed combination factors have no great impact on the average wind speed measurement under certain conditions, this paper can only focus on the basic wind speed. On the basis of above analysis, the experiment is carried out to study how the vertical wind speed influence on the acoustic parametric array sound field, and it found that wind speed will make the sound pressure distribution shift along wind direction, the greater the wind speed, the greater the offset.Then, based on the above conclusions, this paper puts forward the wind speed testing algorithm based on acoustic parametric array, the theoretical derivation about using the linear relationship between wind speed and offset of sound pressure distribution to measure wind speed is carried out, considering the actual test conditions, directly using the mapping relationship to design algorithm, then dealing with data from experiment to build the relationship between wind speed and the offset value, by using neural network’s generalization ability, under the condition of guarantee the fitting effect, it is found that there is a nonlinear relationship between the two, then give some possibility to source for nonlinear relationship. The fitting dealing result is served as the data source of subsequent algorithm testing result.Finally, building wind speed test system, including acoustic parametric array transmitting module, audio receiving module, the wind power generation and testing module, by measuring the sound pressure level on the propagation axis center of acoustic parametric array acoustic field under the wind speed function, find the corresponding offset value on the existing sound pressure distribution curve without wind function, then using the wind speed VS offset mapping relationship curve to find the offset value’s corresponding average wind speed value, with reference to the ultrasonic anemometer measured result, it is found that the wind speed test algorithm based on the acoustic parametric array can be used in testing average wind speed of a wide space, the algorithm can achieve certain performance requirement, and has practical feasibility at some condition.
Keywords/Search Tags:acoustic parametric array, the wind speed test algorithm, vertical wind speed, the sound pressure distribution offset, BP neural network
PDF Full Text Request
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