Sound transmission and its significance for animal vocalization

摘要: 1. Sound transmission was measured in open fields, mixed decidous forest with and without leaves coniferous Dutchess County, New York. Attenuation of white noise pure tones between one microphone close to a loudspeaker another 100 m away, at the same height. Graphs excess attenuation (E.A. dB/100 m) against frequency were obtained 0.15, 1, 2, 5, 10 above ground. An analysis variance conducted estimate effects height, habitat. 2. Height affect sound more than habitat. With source ground (15 cm 1 all frequencies attenuated greater heights. The patterns E.A. as function basically similar habitats. At heights lower better carried, exception that ground, sounds below 2 kHz excessively attenuated. Comparing field forest, trees improved 3 kHz, especially ground. 3. Some general trends can be predicted for maximization distances animal these For an vocalizing higher further travels. Close low are again preferred distances, but must pitched range attenuated, low-pitched sounds, limits which vary some extent habitat, creating ‘sound window’ Morton. This ‘window’ least-attenuated frequencies, only occurring tends somewhat However, producing habitats tested, perch height important habitat determining how far will carry.