Bat sound analysis
With the time expansion technique the calls are recorded, and the file is displayed for instance 10 times slower. The time-expanded sound is analysed in a computer program and the diagram can be stored as a picture-file.
The diagrams (frequency curves) below are recorded with a Petterson D240X bat detector, recorded with a digital Roland R-05 recorder and analysed with the BatScan 9 computer software.
In the recordings below the Y-axis is the sound frequency and the X-axis time. Yellow and red indicate high sound intensity.
Calls used for Echolocation
Brown long-eared bat (Plecotus auritus). These week signals were recorded in a basement. Note the high intensity of the first harmonic. Courtesy Steen Kryger.
Social calls are used in a wide range of situations: for communication within the roost or in air, mother-and offspring communication, male advertisement "song-like" (stationary or in air), or agonistic.
Party-coloured bat (Vespertilio murinus)
Party-coloured bat (Vespertilio murinus). Male advertising song recorded late authomn. High intensity at 14-15 kHz, therefore audible to the human ear. This call can be heard for hours. This call is unique and can be used for identification. The fast low-intensity calls can not be discriminated with a normal bat detector, therefore only 4-5 calls per sec are recognized.
Serotine (Eptesicus serotinus)
Serotine bat (Eptesicus serotinus). above. Social call (A and B) between ecolocalization cells. Note the low frequency of the social calls.
Serotine bat (Eptesicus serotinus). above. Social cal between ecolocalization calls. Note the low frequency of the social calls and the harmonics.
Soprano pipistrelle (Pipistrellus pygmaeus):
Soprano pipistrelle (Pipistrellus pygmaeus). Social sounds from a large roosting colony. Note the irrigular calls, which can be recognised without a detector. The sound is very semilar to a mouse.
Soprano pipistrelle (Pipistrellus pygmaeus). Social call from an individual (male?) located in an old woodpecker hole. Probably an advertising song-like or territorial call.
Soprano pipistrelle (Pipistrellus pygmaeus). Social call recorded during flight.
Soprano pipistrelle (Pipistrelle pygmaeus). Call from a bat sitting in a garden parasol. Note that the frequency is higher than the similar call above.
Nathusius pipistrelle (Pipistrellus nathusii):
Nathusius pipistrelle (Pipistrellus nathusii). Above. Call from a bat sitting in an woodpecker hole. Note the harmonics.
Nathusius pipistrelle (Pipistrellus nathusii). Call from a stationary advertising bat. Note the "trills" with different frequency levels.
Nathisius pipistrelle (Pipistrellus nathusii). Call from a stationary bat in a woodpecker hole. Recorded just before the bat left.
Noctule (Nyctalus noctula):
Noctule (belov). Male advertisement call. The length of the call is approximately 60 msec. The length of the call is revealed from the length of the harmonics, the long part to the right (without harmonies) is an echo.
Noctule. Recorded from within a roost. Partly in the audible area. Can also be heard in the day-time.
Noctule. Two slow trills recorded from the vicinity of the roost. Recorded in May.
Noctule. Fast trill and slow trill recorded from the vicinity of a roost.
Daubentons bat (Myotis daubentoni)
Daubenton´s bat. Between two echolocation calls (note the S-shape) is seen a social call with a lower frequency.