Time expansion bat detectors
Time expansion (TE) detectors are broadband detectors, i.e. they detect all frequencies across the frequency range within which bats are likely to be calling.
They work by digitally recording a brief snatch of bat sound (usually
about one second) and replaying it at a slower rate, usually ten times
slower. Thus a frequency of 50 kHz is lowered to 5 kHz which is within
our hearing range. The advantages are that the entire structure of the
call can be heard enabling species identification using sound analysis
software and the sonograms tend to be of a very high quality. The
disadvantage of the time expansion system is that while the detector is
playing back the slowed-down sounds it becomes "deaf" to any bats flying
past. However, many models also include heterodyne or frequency
division systems which can be heard on one side of your headphones,
enabling you to keep on listening to "live" bat sounds and to decide
when to capture another snatch of bat sound in time expansion mode. Time
expansion detectors tend to be more expensive than heterodyne and
frequency division detectors.
Listen here for examples of calls heard on a Time Expansion detector:
Soprano pipistrelle echolocation calls
Bat Detector Starter Kit
The perfect companion for beginner bat detecting.
If you are a beginner then this kit is a perfect introduction to the detection of bats!
The kit includes:
- Magenta Bat5 superheterodyne bat detector
- Four AAA batteries
- A Field Studies Council 'Guide to British Bats'
The compact Magenta Bat5 has a backlit 4 digit LCD frequency display which is highly visible during the day and night and a top-illuminated large-diameter frequency dial. Bat detectors work by converting the inaudible ultrasonic calls into sounds that we are able to hear (100 to 12kHz). It has an extended low-frequency coverage so it will be able to detect insects and some birds, in addition to bats.
Key features:
- An enhanced oscillator frequency range and low noise
- Easy one-handed operation of volume and frequency controls
- Low power consumption
- Contoured microphone housing for enhanced frequency sensitivity
- Waterproof, short circuit proof headphone output
- Low-level output for connection to a recorder or PC sound card
- Built-in LED torch
- Wrist strap
The FSC guide contains a detailed description of the different calls, flight patterns, and behaviours of the UK's bat species and is an ideal companion for anyone learning to identify British bats.
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