Effects of Ambient Noise on the Vocal Frequency of Chinese Bulbuls,Pycnonotus sinensis in Lin'an and Fuyang City

The study of the ambient noises effect on the vocal frequency of Chinese Bulbuls,Pycnonotus sinensis,was carried out in two cities (Lin an and Fuyang) in China.Based on the noise level (55 db),the samples of each city were divided into two groups of high noise level and low noise level (HN and LN).The records of songs were inputted into the computer,and then the data of principal frequency (PF) of each syllable were gotten through fast Fourier transform (FFT) using a computerized analysis system.The statistical analyses of each syllables PF of the songs were carried out with Mann-Whitney U test to determine differences between HN and LN of each city.The results showed that the minimum PF,maximum PF,the first syllable (SⅠ) and the second syllable (SⅡ) of every song had significant differences between HN and LN in two cities.In Fuyang,the third syllable (SⅢ) had significant difference because of geographic diversity.In contrast HN with LN,the minimum PF,maximum PF and the PF of S1 and SⅡ increased significantly in the high noise level environment.This means that Chinese Bulbuls may avoid the interference of ambient noise with a higher pitch to communicate effectively,and the difference of ambient noises effects on each syllable principal frequency shows that each syllable has different status in communication in noisy environment.