Research On The Radiated Noise Measurement Method Of Underwater Vehicle Propulsion Motors

Ocean noise pollution seriously threat to marine life environment. In order to reduce anthropogenic ocean noise pollution hazards, we need to measure and evaluate complex underwater radiated noise sound source as ships. It can gives the noise characteristics of underwater targets, assess its structural design is reasonable, provide the basis for noise reducing. Structure of underwater vehicle is simple, don't have shock absorbers. Motor noise can be radiated out directly through the housing. It is our ideal object of study. And the existing underwater vehicle manufacturers typically focus on improving the device performance only while ignoring its radiated noise hazards. With the people's awareness of environmental protection, how to reduce the radiated noise of underwater vehicle will also become an important research direction.Underwater vehicles as the representative of the underwater complex sound source measurement is recognized worldwide problem. As we all know, marine natural background noise is large. Coupled with multipath effect and irregular reflection of the seabed and the sea make it very difficult to accurately measure a variety of complex sound sources radiated noise in the epicontinental sea environment. In this paper reverberation method used measuring the radiation noise in the pool has been not being known seriously in the past.Because before scholars generally believe that the ideal reverb conditions can not be formed in a non-anechoic pool. By calculation especially after experimental verification, we found that even in non-anechoic pool does not meet the ideal reverb conditions. Sound source can be measured sound power radiated accurately by the reverberation method. Reverberation method has gradually been used to measure the radiation power of underwater complex sound source.Firstly, in this paper, we theoretically derived from theoretical reverberation method formula of complex underwater sound source in non-anechoic pool. Obtained complex underwater sound source in a rectangular pool of non-anechoic reverberation control area,Relationship between spatially averaged mean squared sound pressure and sound power radiated sound sources. And we analyze the acoustic radiation field in a rectangular pool of typical non-anechoic sound sources. Such as point source, directional sound source,complex sound source. And we measured the acoustic radiation power of each typical sound source in the experiment. By contrast we found that between the results with as measured by the reverberation of sound power and free field measured do not differ by more than 1dB.By contrast measurements under conditions of without spatial averaging, many times averaging, until the 384th averaging. We found that the more the number spatially averaged measurements, the smaller difference of the measurement results between free field. Obtain the relationship between the average number of measuring points in the space with the measuring accuracy Finally, in non-rectangular pond built anechoic measurement system,measuring the underwater vehicle propulsion motors sound power radiated by the reverberation method. By measuring it show that, the underwater vehicle propulsion motors radiated noise is 15dB bigger more than the background noise. Meet the requirements of the measurement signal to noise ratio. Increasing input voltage of the propulsion motors electromotor, the acoustic radiation power measured increases linearly. Radiated noise of underwater vehicle propulsion motor is mainly line spectrum noise of the motor.Reverberation method can accurately measure the radiated noise.