Echolocation - Nature's Own Radar
Although bats can see and hear in the same way as us, they can also picture the world by interpreting the echoes of the high-pitched calls that they emit - well enough to be able to locate, identify and capture the tiniest insects. Children can detect sounds up to about 20kHz (1kHz is 1,000 cycles per second), but this is lower than the frequencies produced by most species of bat; the bats which feed on the smallest insects use the highest frequencies, i.e. a shorter wavelength (rather like casting a finer net), to find their prey, and one species, the Short-Eared Trident bat (cloeotis percivali), transmits at over 210kHz, but many near-tropical species operate well above 150kHz, e.g. the Funnel- , Notch-Eared and Tube-Nosed bats that inhabit parts of Central America, the Caribbean and South-East Asia, and Golden-Tipped bats of the East Australian seaboard. Spotted bats, some Free-Tailed and Sheath-Tailed bats, on the other hand, echolocate as low as 9-15kHz, and can be quite audible to us.

Individuals tend to broadcast within narrow limits of the norm for the species - i.e. at the wavelength best suited for detecting their usual prey - but often use slightly lower frequencies and/or a broader range for social communication. Many species use an almost constant frequency (CF), but others modulate the frequency of the call (FM) - often starting high and finishing low: this 'sweep' provides more detail about the shape and substance of the objects (and insects) in front of them; the calls of many species are a combination of CF and FM. Some bats (e.g. Lesser Horseshoe) employ the 'Doppler Shift' effect - transmitting a level call, and interpreting the apparent changes in the pitch of the echo caused by relative movement - so efficiently that they can identify an insect just from the characteristic report of its wing-beats.

All the microchiroptera species use sonar/echolocation, and calls always originate in the larynx, but are then either channelled through the specially-adapted nose (e.g. horseshoe bats) or - more usually - the mouth parts (e.g. free-tailed and vespertilionid bats). Although usually completely inaudible to us, calls have so much initial energy that the bat momentarily has to disable its own hearing mechanism while transmitting.

Types of Bat Detector
Three types of detector are in general use, each having its own particular advantages:-

Heterodyne This is the most widely-used receiver and easily the best-suited for the hobbyist; it operates on a similar principle to a radio and is tunable - with a spread (bandwidth) around the selected frequency; the detector mixes the incoming signal with the waveform generated by an internal ('local') oscillator - which results in a difference between the two frequencies which is audible to us; because pitch, volume and duration are all reproduced in the same way as the audio output of a radio, the calls of the different species can easily be recognised.
Click on the speaker icon to hear a Pipistrelle bat through a heterodyne detector (allow a few moments for the file to load).

Frequency Division These detectors operate by dividing the call frequencies by a fixed factor to produce an audible click of a constant volume. Simpler than heterodyne but very reliable, often with switchable frequency ranges.

Time Expansion Bat calls are recorded (usually digitally) then played back at a much slower speed, i.e. decreasing the frequency to an audible level, and - in so doing - lengthening the individual notes of the call; particularly suited for scientific observations and computer analysis.

More About Ultrasound
One difficulty of listening-in to the world of bats is that the higher the call frequency, the greater the rate of attenuation through the atmosphere: lower frequency calls travel much further for the same initial energy level. (It is for the same reason that the very low frequency calls of whales carry many hundreds of miles through the ocean). Although the efficiency of a detector is dependent on the sensitivity of its microphone and internal amplification, the practical range for listening to bats is usually less than 20 metres, so - as well as the equipment - the species, immediate environment, weather conditions and the type of call (social or hunting), etc., all influence the effective reception range.

There are about 1,000 species of bat worldwide, around 30 of which are found in Europe - and 17 of these inhabit or visit the British Isles; below is a table of the more common species with their geographical distribution and typical call frequencies.
Species Scientific name Distribution Hunting* Social
Barbastellebarbastellus barbastellusS. Britain, W. Europe56kHz30-40kHz
Bechstein'smyotis bechsteiniS/Central England, W. Europe112-40(50)kHz34-100kHz
Brandt'smyotis brandtiiS. Britain, Central/E. Europe, Central Asia64-41(45)kHz30-80kHz
Brown Long-Earedplecotus auritusAll Europe except far North63-34(40)kHz25-50kHz
Daubenton'smyotis daubentoniiAll Europe except far North50kHz35-85kHz
Free-Tailedtadarida teniotisMedit. Europe20kHz20-45kHz
Greater Mouse-Earedmyotis myotisSW England (very rare), S. & W. Europe45kHz20-30kHz
Greater Horseshoerhinolophus ferrumequinumSW England, SW Wales, Medit. Europe82kHz70-120kHz
Lesser Horseshoerhinolophus hipposiderosS. & W. England & Wales, Ireland, S. & W. Europe110kHz100-120kHz
Leisler'snyctalus leisleriCentral England, Ireland, S. Europe32-25(30)kHz20-100kHz
Grey Long-Earedplecotus ausrtriacusS. Central England, W. Europe63-30(50)kHz30-50kHz
Nathusius' Pipistrellepipistrellus nathusiiS. &E. England, Europe except W. Penins & far North49-38(39)kHz38-70kHz
Natterer'smyotis nattereriiAll Europe except far North70-30(45)kHz35-80kHz
Noctule (or Great)nyctalus noctulaEngland, Wales, Central & E. Europe20kHz20-45kHz
Common Pipistrellepipistrellus pipistrellusAll Europe except far North48kHz20-30kHz
Soprano Pipistrellepipstrellus pygmaeusAll Europe except far North55kHz20-30kHz
Serotineeptesicus serotinusS. & E. England, W. Europe27kHz15-65kHz
Whiskeredmyotis mysticanusBritain except Far North, Europe except W. Penins 64-41(50)kHz30-80kHz
*The x-y(z)kHz format indicates very distinct frequency-modulated calls (FM, i.e. calls with a varying pitch), with high-low and peak intensity values.

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Click here for our collection of heterodyne and frequency-division bat detector schematics and diagrams. Bat detector circuits showing different transducer and amplifier circuit arrangements, with parts part numbers, kit availability. Part No.... Bat detector prices in UK, US, European countries including delivery postage, taxes VAT or TAV General Bat sounds and call analysis... Bat detector calibration... How a bat detector works... microphone pre-amp frequency converter. Bat detector plans Heterodyne with your computer's hard drive... À l'écoute des chauves-souris... an 'ultrasonic-to-RF' converter. Heterodyne detector D.I.Y. bat detector Comparison of Magenta kit 861 Mk.2 Bat Detector The Transtronics Ultrasonic translator SK-207; Ready-built bat detectors Pettersson Elektronik AB BVL Von Laar Tranquility II ; Semafor UF-220 dual oscillator heterodyne; Belfry model The Anabat. Stag electronics (Bat box III). Ultra sound bat detectors. continuous sampling with compresssion / de-compression to give a very slightly delayed signal brought into audible range.. computer memory and special software pitch detection, gate/chop, time / tuning control, compression/expansion, pitch change, reverse, fade, sample rate convert, cut, ..nyquist analysis, fourier...Ultrasonic ultrasound lm386 741 op-amp operational amplifier amplification voltage current microphone, resistor mylar, ceramic or electrolytic capacitor...observe polarity amplifier... components from radio shack transducer kit oscillator audio flip flop gain db decibel frequency modulaltion constant cf fm transistor opamp mosfet piezo piezoelectric transducer microphone kit designs schematic capacitor transistor filter bandwidth vhf vlf ulf pcb printed circuit board schematic diagram and layout wiring project similar to a transistor radio and integrated circuit (IC) chips, phono jack socket built-in loudspeaker , .25W, low current 6.5mA circuit assembly instructions or ready-built
the oscillator signal and bat call signal are of approximate equal frequency, differing only a few kHz, with heterodyning ...Humans can hear only up to 20 kHz; using harmonics, varying the call ...bat detectors brings the frequency of the bat call down to a audible level... The Greater Horseshoe bat being about 80 kHz, while the Lesser Horseshoe Bat. Thus if the bat detector is set to 50kHz and an incoming bat call is at 48kHz ... of 'clicks' when listened to with the bat detector set to 45 to 50 kHz. ..Bat call in fast Fourier transform (FFT) display ... Setting, N, Duration (ms), FME (kHz), HF (kHz), LF (kHz), IPI (ms) .Harmonics.Bat Vocalizations - search phase call at 64 kHz is played back at 4 kHz. some bat calls do not need to be lowered as they are already within our hearing range ... Some bat species can hear up to 212kHz. Other animal species can hear a full octave .... of how bat detectors work, design and bat call analysis. ...
frequency division detector is a wide band device ... detectable bat sounds without the need to tune the detector to any particular frequency, but lose amplitude and pitch information. Heterodyne detectors.. ultrasonic sound in the analogue region, convert a relatively small range of frequencies at any given setting... The frequency division detector works in the digital domain, converting the full spectrum of sound that the transducer is able to detect. all of the ultrasonic sounds around without missing anything due to narrow tuning. .. additional resistor ... in series with a 10uf capacitor to reduce the gain of IC-1. A resistor / capacitor combination to increase gain.ystem gain can vary anywhere from 400 to 40,000Hz Heterodyne detector Oscillators and mixers Frequency display simple amplitude retaining division detector.... advanced amplitude retaining division detector
Barbastelle Brandt's/Whiskered Brown Long-Eared Daubenton's Leisler's Lesser Horseshoe Natterer's Noctule Pipistrelle Serotine Bechstein's Greater Horseshoe Grey Long-Eared Greater Mouse-Eared Nathusius' Pipistrelle The pipistrelle, Pipistrellus sp. (Pipistrellus pipistrellus and P. pygmaeus) The noctule, Nyctalus noctula The Daubenton's bat Myotis daubentonii Natterer's bat (Myotis nattereri) The brown long-eared bat Plecotus auritus The serotine bat Eptesicus serotinus The Leisler's bat (Nyctalus leisleri)
Most sensitive heterodyne detectors... This bat detector is a frequency division instrument. Frequency division detectors translate ultrasonic sound by digitally reducing frequency to an audible tone. pipistrelle bats emits ultrasonic sound in the range of 20 - 120 kHz dividing that frequency by 16, the new frequency range is 600 Hz to 8 kHz, within our hearing range. division is digital, so amplitude information is lost. Ultrasonic fequencies processed by the detector convert the incoming signals to clicks and chirps and chonks. view circuit schematic diagram includes integrated circuits, or ICs. table of bat call frequencies; other animals and insects, (moths)
The signal from an ultrasonic transducer LM386 audio amplifier, signal gain of 200. another LM386, a .05 uf capacitor. IC-2 has a gain of 20; 7 stage CMOS digital divider circuit otherwisw known as a zero crossing detector. The divide-by-16 output is sent through the potentiometer volume control. output via high impedance ceramic earphone crystal set type... is connected to the output of the level control. 9 volt battery or 1.5v. Circuit for microphone/transducer detuning a piezo-electric microphone
Echolocation annd the Greater Moustached batat - Mice can hear up to 100 kHz The highest frequency animals are whales and tropical bats
.Echolocation in Bats - high frequency detector, responded at 100 kHz, the limit of this instrument. Variation in echolocation calls Frequencies recorded from time expansion ...echolocation frequencies for North American vespertilionid bats at ... frequency period of most energy duration in this species. kHz m/s ...
Low-Frequency Echolocation the Bat Tadarida ...Fast-flying, aerial-hawking bats require high-intensity echolocation; also feeds in open habitats and uses low-frequency (11 kHz) echolocation; Humans hear sounds up to 20 kHz, while most bats use a much wider and higher spectrum ... bat echolocation calls can be very high in frequency range, ...Frequency of bat sonar ; can detect frequencies as high as 212,000 Hz; pipistrelles horseshoe see also under tragus ear chiroptera echo location insect moth mosquitoes; bat conservation and protection laws
murata piezo piezoelectric transducers microphones, etc. most species of bats ....frequencies 60 kHz, high duty cycle echolocators in... these bats can find their way about at night and locate their food by using a high frequency echolocation system; the allometry of echolocation call frequencies of insectivorous/chiroptera species
Among high-duty-cycle bats, rhinolophus mehelyi (fore-arm 53 mm; echolocation frequency 109 kHz) is one of the. largest rhinolophids in Asia and Europe ...Hearing in the FM-bat as opposed to the high-frequency echolocation. signals, directive calls cover ..... the frequency range of 5-142 kHz, bats 4-6 in the range of. 15-55 kHz or constant frquency CF amplitude and frequency plots. bat vocalizations can be heard by clicking on speaker The pulse rate is about 5 per second, Model Semafor UF-220: Range 10kHz-220kHz
Controls Frequency, volume, bandwidth, on/off switch.
Output Two phono sockets, .25W built-in speaker, signal LED.
Power 9v pack PP3; 6.5mA at mid-settings. pre-amplifier gain aerial coil tuning inductance
Size 145x60x45mm.
(Headset & battery are included).";
bat detector equipment   bat detectors, echolocation   bat detector & ultrasonic echolocation   bat detectors, echolocation and ultrasonic devices   Bat detectors are electronic devices that convert the high-pitched sounds that bats use to fly in the dark into audible sounds
Choosing a bat detector there are several factors to consider which bat detector to buy.
Bat Detecting. The most widely available bat detectors work by heterodyne. There are several heterodyne bat detectors available from around £60
.. ultrasonic chirps, smacks and clicks.
Frequency Division Detectors zero crossing detector. whole ultrasonic frequency range not need tuning. Spectrograms two oscillator = super heterodyne. type of detector Noctules use low frequencies of around 20 kHz, Leisler's and Serotine similar frequencies. Myotis species, as calls in the range of 40-60 kHz Although there are a number of variations, all heterodynes mix an incoming signal with the waveform of the tunable oscillator, within the receiver. The result is a difference between the two frequencies which is low enough to be audible to human ears. Semafor's UF series uses a dual-oscillator detector, which typically draws just 6-9mA using multple feedback state-variable filters, mosfet quad opamp. Cmos oscillator or flip flop data latch. Bipolar transistors or BJT, UJT bc108 bc107, bc109, bc179. FET transistors. multiple feedback types... bandpass, notch, low pass, and high pass filters using LF347 op-amp electret microphone
if the bat detector is set to 50kHz and an incoming bat call is at 49kHz
.Bat detectors are devices that pick up the ultrasonic signals sent out by bats. Like radio receivers, bat detectors also have a tuning dial Bat Boxes and Detectors 'listen' to the bats' ultrasonic echo-location noises, ...Batbox : downloads of bat sounds hard drive sample rate .wav files sounds repetition click bat ultrasonic kHz price vat wildlife insects crickets, click call chirp.... heterodyne oscillator echo location amplify... noise pocket circuit detector.. technical terms... decibel amplitude volume ulf vlf elf bats very high frequency selection mark space transducer. Price including vat. There are heterodyne detectors, Frequency division detectors and time expansion detectors. integrated circuit or discreets
The Greater Horseshoe bat being about 80 kHz, Lesser Horseshoe Bat 110-120 kHz. Spectrographic Analysis time expansion detectors PC sound analysis. Sonograms enable sounds to be compared and analysed. From a bat ultrasonic calls. Pipistrellus pipistrellus Midge pipistrelle Pipistrellus pygmaeus Nathusius' pipistrelle Pipistrellus nathusii Barbastelle Barbastella barbastellus Brown long-eared bat Plecotus auritus Grey long-eared bat Plecotus austriacus Parti-Coloured Bat Vesertillio murinus Greater-mouse Eared Bat Myotis myotis Greater horseshoe bat Rhinolophus ferrumequinum Lesser horseshoe bat Rhinolophus hipposideros Whiskered bat Myotis mystacinus Brandt's bat Myotis brandtii Natterer's bat Myotis nattereri Bechstein's bat Myotis bechsteinii Daubenton's bat Myotis daubentonii Serotine Eptesicus serotinus Noctule Nyctalus noctula Leisler's bat Nyctalus leisleri Common pipistrelle
Time Expansion Detectors spectrum no tuning is necessary. slowed down signals can be saved and then recorded tape PC Species Identification with a Heterodyne Detector Pipistrelles... 45-55kHz irregular vary in pitch. Daubenton's, Whiskered and Brandt's Bats fast repetition rates. Natterer's Bat though is faster, but more quiet and irregular other Myotis species. The Long eared bats also have faster repetition rates than other Myotis species, but the calls are much quieter The Horseshoe Bats have echolocation calls higher frequencies than other species most bat echolocation calls are high in frequency, well beyond the range of human hearing, but we can hear the echolocation calls of some species. Spotted bats (euderma maculatum), for example, produce calls that cover frequencies from 9 kHz to 15 kHz. Like the calls of many free-tailed (tadarida spp.) and Sheath-tailed bats (e.g. Old World taphozous spp.), they are quite audible to us.