Ultrasonic emissions of bats (Mammalis Chiroptera ) are formed by both social calls and echolocation pulses. As to the latter ones, every bat species exploits peculiar morphological features in the time and frequency domain, so as to be characterized by a unique echolocation pattern. For this study, echolocation pulses and social calls of two species ofvespertilionid bat have been recorded twice, first in laboratory and then in a natural environment. The signals of adult specimens of Pipistrellus kuhlii and Hypsugo savii are described and analysed. These species, quite common in Italy, are externally similar and have antropic habits, covering a very much similar echological role. Their distinction is normally based on areal spreading, physical size and morphology and acoustic classification criteria. The last criterium is often used in the field recording condition after the heterodyning conversion has made possible the audition of the ultrasonic pulses to the human ear. The ultrasonic sounds were checked and detected with a Pettersson Ultrasound Detector D-100 connected to the Schlumemberg magnetic recorder Euromag 1. The recording rate of magnetic tape was set to 76 cm/s. In order to apply the DSP analysis to the recorded signals, the running of the magnetic tape was then set to 4.75 cm/s., making possible the exploitation of the nominal 8 kHz spectrographic standard range (the virtual interval of 1 kHz thus corresponding to a real interval of 16 kHz) . As to the laboratory recording condition, the specimens were recorded while fliyng inside a 7x4x3 m room. A wide band microphone was set at 1.5 meters from the floor near the central point of the longest wall. As to the field condition, the same microphone was set near the roosts of specimens of the two species. Measures for time and frequency were taken through average power spectra of the costant frequency part ot the signals, or through power spectra at the extreme ends of a frequency modulated part of the signal, and measures about the rates of emission were taken simply counting the occurrences of the omogeneous signal units whithin a second. A comparison is made between the spectrographic features of these signals in order to value advantages and disadvantages of the two recording conditions
Methodological considerations on the acoustic signal analysis for two species of bats (chiroptera vespertilionidae)
Zmarich C;
1997
Abstract
Ultrasonic emissions of bats (Mammalis Chiroptera ) are formed by both social calls and echolocation pulses. As to the latter ones, every bat species exploits peculiar morphological features in the time and frequency domain, so as to be characterized by a unique echolocation pattern. For this study, echolocation pulses and social calls of two species ofvespertilionid bat have been recorded twice, first in laboratory and then in a natural environment. The signals of adult specimens of Pipistrellus kuhlii and Hypsugo savii are described and analysed. These species, quite common in Italy, are externally similar and have antropic habits, covering a very much similar echological role. Their distinction is normally based on areal spreading, physical size and morphology and acoustic classification criteria. The last criterium is often used in the field recording condition after the heterodyning conversion has made possible the audition of the ultrasonic pulses to the human ear. The ultrasonic sounds were checked and detected with a Pettersson Ultrasound Detector D-100 connected to the Schlumemberg magnetic recorder Euromag 1. The recording rate of magnetic tape was set to 76 cm/s. In order to apply the DSP analysis to the recorded signals, the running of the magnetic tape was then set to 4.75 cm/s., making possible the exploitation of the nominal 8 kHz spectrographic standard range (the virtual interval of 1 kHz thus corresponding to a real interval of 16 kHz) . As to the laboratory recording condition, the specimens were recorded while fliyng inside a 7x4x3 m room. A wide band microphone was set at 1.5 meters from the floor near the central point of the longest wall. As to the field condition, the same microphone was set near the roosts of specimens of the two species. Measures for time and frequency were taken through average power spectra of the costant frequency part ot the signals, or through power spectra at the extreme ends of a frequency modulated part of the signal, and measures about the rates of emission were taken simply counting the occurrences of the omogeneous signal units whithin a second. A comparison is made between the spectrographic features of these signals in order to value advantages and disadvantages of the two recording conditionsI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
