Microphone Array Signal Processing For Bird Song Index

Ecological assessment plays an important role in protecting the ecological environment and guiding the construction of ecological civilization.As a kind of widely distributed environmental indicator,birds can reflect the change of ecological environment in the habitat.As a non-invasive monitoring method,bird acoustic monitoring could be used to evaluate the level of regional ecological environment.In this dissertation,a method of microphone array processing for the calculation of bird acoustic index is introduced.From the perspective of soundscape ecology,the bird acoustic index uses acoustic complexity to replace species complexity,and could evaluate bird species diversity in this region practically without prior knowledge.Due to the complexity of the field environment and the limitation of the field and equipment,the distances between the location of bird's voice and the sound acquisition equipment are different,resulting in different signalto-noise ratio of the bird sound signal.In view of this situation,we first explored the correlation between bird acoustic index and signal-to-noise ratio,and found that different bird acoustic index presented different changes with the change of distance.Therefore,it is necessary to enhance the bird signal in the collected bird sound data to reduce the influence of distance on bird acoustic index,so that the bird acoustic index could reflect the diversity level of birds in this region more accurately.Then,this dissertation studied the array signals of birds and the microphone array signal processing method for bird acoustic index.This method used the generalized cross-correlation algorithm weighted by phase transformation to estimate the time difference of arrival.Based on the generalized sidelobe canceller structure,the bird sound signal was enhanced and the signal-to-noise ratio of the bird sound signal was improved,so as to make the obtained bird sound signal purer and improve the robustness of the bird acoustic index.Finally,the effectiveness of this method was verified by simulation experiment and measured data processing.The results show that our enhancement method could enhance the bird sound signal and also has a good suppression effect on the mechanical noise.At the same time,this method could improve the robustness of bird acoustic index.