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A heterodyne function is often also built into the other types of detector. A heterodyne bat detector simply shifts all the ultrasound frequencies downward by a fixed amount so we can hear them. A "heterodyne" is a beat frequency such as can be heard when two close musical notes are played together.
At the UK National Bat Conference, Wildlife Acoustics announced the Echo Meter handheld bat detector. [8] The device will be available in December 2011. The detector is capable of monitoring for bats using heterodyne, frequency division or Real Time Expansion (RTE). RTE is Wildlife Acoustics proprietary technique for shifting bat sounds to the ...
A heterodyne bat detector will only handle a small range of bat frequencies, so it is necessary to keep retuning the heterodyne frequency to find the point of maximum loudness or, in the case of bats with a hockey stick call, the frequency which gives the lowest sound. This gives the lowest plop sound from the CF end of the calls.
P. pygmaeus (55 Pip) call on heterodyne bat detector, recorded in stereo 187 kHz The frequencies used by this bat species for echolocation lie between 53 and 86 kHz, have most energy at 55 kHz and have an average duration of 5.8 ms.
Ultrasound avoidance is an escape or avoidance reflex displayed by certain animal species that are preyed upon by echolocating predators. [1] Ultrasound avoidance is known for several groups of insects that have independently evolved mechanisms for ultrasonic hearing.
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"Heterodyne" signifies more than one frequency, in contrast to the single frequency employed in homodyne detection. [1] The comparison of the two light signals is typically accomplished by combining them in a photodiode detector, which has a response that is linear in energy, and hence quadratic in amplitude of electromagnetic field.
Typically, only one of the heterodynes is required and the other signal is filtered out of the output of the mixer. Heterodyne frequencies are related to the phenomenon of "beats" in acoustics. [2] [5] [6] A major application of the heterodyne process is in the superheterodyne radio receiver circuit, which is used in virtually all modern radio ...