Many have reported that sasquatches will take food left for them at a feeding station but will discontinue taking the food if a trail cam is aimed at the same feeding station. Coupled with the overall lack of success with trail cameras, evidently something is wrong with them. I read one comment that trail cams actually create the opposite of the desired result in that they drive away sasquatches. One wonders, "what is causing this?" The explanation for this dilemma could be an inherent flaw in motion sensors.
Here are various methods used as motion triggers in sensor technology:
(pictured above) Infrared detector mounted on circuit board, along with photoresistive detector for visible light
There are several motion detection technologies in wide use:
1. Passive infrared (PIR)
Passive infrared sensors are sensitive to a person's skin temperature through emitted black body radiation at mid-infrared wavelengths, in contrast to background objects at room temperature. No energy is emitted from the sensor, thus the name "passive infrared" (PIR). This distinguishes it from the electric eye for instance (not usually considered a "motion detector"), in which the crossing of a person or vehicle interrupts a visible or infrared beam.
These detect motion through the principle of Doppler radar, and are similar to a radar speed gun. A continuous wave of microwave radiation is emitted, and phase shifts in the reflected microwaves due to motion of an object toward (or away from) the receiver result in a heterodyne signal at low audio frequencies.
An ultrasonic wave (sound at a frequency higher than a human can hear) is emitted and reflections from nearby objects are received. Exactly as in Doppler radar, heterodyne detection of the received field indicates motion. The detected doppler shift is also at low audio frequencies (for walking speeds) since the ultrasonic wavelength of around a centimeter is similar to the wavelengths used in microwave motion detectors. One potential drawback of ultrasonic sensors is that the sensor can be sensitive to motion in areas where coverage isn't desired, for instance, due to reflections of sound waves around corners. Such extended coverage may be desirable for lighting control, where the point is detection of any occupancy in an area. But for opening an automatic door, for example, one would prefer a sensor selective to traffic in the path toward the door.
4. Tomographic motion detector
Tomographic motion detection systems sense disturbances to radio waves as they pass from node to node of a mesh network. They have the ability to detect over complete areas because they can sense through walls and obstructions.
Of the four mentioned above, only the first one is passive. # 1 (PIR) looks for body heat and does not emit anything. All the others are actively emitting something. The above description seems to say microwave sensors emit radiation which in turn creates a low audio sound and ultrasonic sensors emit a high frequency sound that likewise is received back as a low frequency sound. In Browning's e-mail reply to Thomas they said,
"Our cameras do not emit any frequencies that are noticeable by animals"
That implies the cameras do create audio frequencies, but Browning is saying it is not at a threshold that animals can hear. Is the verdict still out on that? Of course we can't here it. "Heterodyne" mentioned as a result of the microwave sensor is a frequency beyond human hearing. I suppose one should specifically ask the manufacturer which motion sensor technology does Browning incorporate in its game cams.
Of all the motion sensors, I wonder if trail cams with passive infrared is the way to go? And do makers of game cams even exclusively use that type of motion sensor technology? Maybe none do since at the above link it says most motion sensors use dual modes of sensing. It states,
"Many modern motion detectors use combinations of different technologies. While combining multiple sensing technologies into one detector can help reduce false triggering, it does so at the expense of reduced detection probabilities and increased vulnerability. For example, many dual-tech sensors combine both a PIR sensor and a microwave sensor into one unit. In order for motion to be detected, both sensors must trip together. This lowers the probability of a false alarm since heat and light changes may trip the PIR but not the microwave, or trees may trigger the microwave but not the PIR. If an intruder is able to fool the PIR or microwave, however, the sensor will not detect. Dual-tech sensors are only as strong as their weakest link."
Question: are microwave sensors creating infrasound? The microwave motion sensor sends out alternating frequencies of radiation, but the receiver detects the changes in a low audio frequency. Likewise, reading what it says about ultrasonic motion sensors, it says it sends out high frequency sounds, but it says just like microwave motion sensors it too is received back in low audio frequencies.
Infrasound is sound waves with frequencies below the lower limit of human audibility (low audio frequencies). It's widely believed that sasquatches produce infrasound vocally, and many also speculate they might communicate with each other via infrasound. If a lot of trail cams are using microwave or ultrasonic motion sensors then perhaps sasquatches are hearing low audio frequencies. Ultrasonic sound waves are at a frequency above the upper limit of human hearing. We can't hear infrasonic or ultrasonic audio frequencies but perhaps bigfoot can, at least infrasonic hearing is very likely. It's a fact that there are animals that can hear beyond the range of human hearing.
So, sasquatches might not simply be hearing the hum of an electrical device, as some speculate as the source of the problem, but it could be the motion sensor itself is creating the sound they are hearing, which if that is the case there would be no way to quiet a trail cam employing that mode of sensor to detect movement. Therefore, we need to research the trail cameras we contemplate deploying in the field.
Additionally, this opens up new strategies if the motion sensors on trail cams is the culprit behind not getting video at feeding stations, like figuring out how to employ camouflaged video cameras minus sensor technology aimed at an established feeding station or likely sasquatch crossing/habitat. Any ideas on how to make that work? That could be a means to test this theory. If successful it would lend credence to the noisy motion sensor theory.