Study On Sound Source Localization Method Based On Bio-inspired Time-delay Amplification Mechanism

High-precision sound source localization(SSL)devices are widely used in civil and military fields.Most of SSL methods use interaural intensity difference(IID)and interaural time difference(ITD)cues from the signals which arrive at different sensors.Magnitude of both IID and ITD will decrease as the distance between the sensors decrease.The precision of those detection devices based on ITD of the incident sound,such as intelligent robot ear and towed sonar,are limited by the aperture of sensor array directly.Therefore,under the constraint of size,how to improve the performance of the SSL system desiderates to be resolved,especially for the low-frequency signal targets.According to the SSL requirements from different application fields,new technologies are wanted to satisfy the requirements.A kind of fly called Ormia ochracea,has a remarkable ability to detect the direction of calling from the crickets(the host),despite of the small body.Preliminary studies suggest that there exists a unique coupling mechanism which may magnify the ITD of the received sound signals.This mechanism is equivalent to increase of the distances between two ears by tens of times.So,this mechanism provides a clue for us to develop new high-precision sound source localization system.This present dissertation is completed under this background and includes the following four components.Based on the previous research on above coupling mechanism with mechanical and electrical models,an algorithmic model is proposed.The dimension of the model is extended to satisfy different scope of tasks.The equivalence between algorithmic model and mechanical model are analyzed.The characteristic of the high-dimension model is analyzed and we find out that the model has two and only two natural damped frequencies despite of its dimension.The relationship between the magnification of the ITD and the natural damped frequencies are deduced.We find out that the magnification factor is dependent on the excitation frequency and the natural damped frequencies.This finding may reveal the essence of the magnification of coupling mechanism.The choice of the magnification factor of ITD with high and low excitation frequencies is discussed.On the basis of theoretical research on the high-dimensional algorithmic model,a multi-stage algorithmic coupling SSL method is proposed.The system are equipped with forward-backward filter and phase shifter as necessary preprocessing steps.The weighting functions of the generalized cross-correlation method are discussed and find out reasonable method for SSL.The magnification factor of the multi-stage coupling method is deduced.The method breaks through the limitation that the difference of two signals must be in one period.With proper magnification factor of ITD,the precision of SSL can be improved remarkably.The determination condition of the iteration in the method is also discussed.The SSL ability under noise environment is considered.Aiming at characteristic of harmonic signals,the first-peak method is adapted into this system,which can effectively reduce the requirements of SNR.Based on the study on the method above,the the multi-stage algorithmic coupling SSL system is designed and the SSL ability based on this coupling system are studied.The hardware aspect,which includes the choices of the sensors,spatial layout and acoustic filed condition are analyzed.The detectable distance between the sensors are analyzed,the proposed system has larger range than traditional sensor array.The performance of single-and multi-stage SSL with this coupling system are compared.An experiment platform of the multi-stage algorithmic coupling system for SSL is built.In order to validate above theoretical research,experiments with this system are conducted.The characteristic of the magnification of ITD is verified,the magnification factor is close to theoretic value.The effectiveness of the multi-stage algorithmic coupling system is validated,and the ability of SSL is improved remarkably.Under the condition of simulated undersea noise environment,the system still has enough ability of SSL.These results of the experiments demonstrate that the theoretical analysis is correct and the SSL system is effective.