Study On Testing Method Of Acoustic Performance Of Underwater Acoustic Material Based On Virtual End-fire Array Technology

Underwater acoustic material plays an important role in Underwater Acoustic applications.With the development of sonar technology,underwater acoustic material operating frequency gradually to low development,the study of low frequency sound measurement launching acoustic performance materials become the main trend in the field of underwater acoustic measuring current.Acoustic performance measurement of underwater acoustic materials include measurement parameters of the reflection coefficient,transmission coefficient,absorption coefficient,as long as get a transmission and reflection coefficients,other acoustic parameters can be deduced.The methods of underwater acoustic material acoustic performance measurement in Medium and high frequency had Development more mature.With the decline in the frequency of measurement,the traditional measurement methods lead to that boundary reflected wave and Diffracted wave edge of the specimen have can not be ignored to experimental results.Therefore,carry out the measurement and research of underwater acoustic material sound properties of low frequency is an urgent need to address the problem.By the sound of the parametric array works inspired groundbreaking proposed a new means for measuring acoustic performance underwater acoustic material,let us call it "virtual end-fire array technology." By mimicking the formation process of acoustic parametric array of virtual source end-fire array,take the transmitting transducer to continue moving along the measuring direction get the received wave of different positions.The received wave after amplitude weighting process with the same frequency phase superposition,it could eliminate the received wave of outside transmitting transducer direction of movement.This approach enhances the signal strength,improved signal to noise ratio of the received signal at low frequencies,to improve the directivity of the transmit beam.To make the virtual end-fire array technique works best in a non-free field measurement environment,using MATLAB simulated virtual end-fire array directivity diagram.Through the analysis of the main lobe open-angle and side lobe suppression,design of the best virtual end-fire array,cause the transmit beam opening angle is less than the critical value,to ensure that the received signal can effectively avoid the influence of the boundary reflected wave.In one dimension 4m × 1.4m × 1.2m steel tank measure and analyze the size of 1m × 1m sound absorption wedge of the acoustic properties.Experimental results show that the virtual end-fire array technology compared to the conventional method can effectively reduce the measurement frequency limit.Meanwhile,comparative test results and measurements under free field environment with good consistency,verify the validity of the technology used in underwater acoustic material acoustic performance measurement.Moreover,launched a class A uncertainty calculation.