Audibility Capacity of Mosquitoes Male mosquitoes have a highly developed sense of hearing, though it is much different from that of humans. Male mosquitoes rely on their sense of hearing for breeding purposes. Because of the link between hearing and mating behavior, as well as their impact on human health, the hearing abilities of mosquitoes has been the subject of much study. The limit of mosquito hearing is approximately 2,000 Hertz.

Mosquito Hearing
Mosquitoes are equipped with two feathery antennae on their head, and they use these to hear. The antennae are attached at the base to circular structures called Johnston’s organs. Mosquitoes engage in an active, metabolically driven hearing; the antennae filaments are tuned, and adjusted to various frequencies and sound levels. For a long time, females were thought to be deaf, but a 2006 study by Gabriella Gibson and Ian Russell, published in “Current Biology,” demonstrated that females can hear.
Flight Tones
The buzzing sound of mosquitoes is caused by the vibration of their wings, and is termed a flight tone. The flight tone of female mosquitoes is about 400 Hertz, and males have hearing that is tuned selectively to the frequency range of 300 to 400 Hertz. When a male perceives a female’s flight tone, he actively pursues her for mating.
Courtship
Mosquitoes have exquisite control over their wings, and by changing the rate they beat their wings, they can change the frequency of the buzzing. The study by Gibson and Russell showed not only that females can hear, but that courting pairs will synchronize their tones. Consistent with the hypothesis that these tones are used in courtship, the frequency of the flight tones of same-sex pairs may converge initially, but ultimately diverges a great deal. In a more recent study by L. J. Cator et al., published in a 2009 issue of “Science.” they demonstrated that one species, Aedes aegypti, was capable of hearing a much wider range of frequencies than previously thought possible. When they analyzed the synchronized tone of courting pairs, it was found to be approximately 1,200 Hertz. The researchers investigated the structure of the hearing apparatus, and found that the cells were responsive to frequencies as high as 2,000 Hertz. Mated females were found to be less responsive to the flight tones of males.
Ultrasonic Mosquito Repellents
Some commercial products exist that claim to repel mosquitoes by emitting ultrasonic sounds. Some radio stations also have tried broadcasting these ultrasonic sounds, thus repelling mosquitoes from their listeners. These sounds often are emitted at 15 kilohertz, which is above the upper limit of sensitivity for most adult humans, so it mostly goes unnoticed. Unfortunately, according to a review of 10 field studies by A. Enayati et al., published in a 2010 issue of “The Cochrane Library,” there is no evidence to suggest these devices repel mosquitoes. Bart Knols, advisory board chairperson for the Dutch Malaria Foundation and entomologist, echoed these findings, adding that there was “no scientific evidence whatsoever” to demonstrating the effectiveness of such devices. Knols went further, adding that mosquitoes aren't even repelled by the frequency produced from dragonfly wings. Predators of mosquitoes, dragonflies produce a flight tone of 20 to 170 Hertz, which is much lower than the tones emitted by ultrasonic repellant devices.

Nuguid, Mia Carmela P.
BSEd 3-B Physical Science
Assignment #3 (Dec. 01, 2015)

There are 15 species of hedgehogs, most of which are found in the wild in Africa, Asia and Europe. These little, rodent-like critters are covered in spines, which provide them a great deal of protection. Their eyesight is poor, but their keen hearing and sharp sense of smell help them get by quite well in the world.

No Glasses Necessary
Compared to humans, hedgehogs have poor eyesight. That's OK, however, because they don't really use their eyesight all that much. Their limited eyesight allows them to see the outlines of objects, such as a tree, and their color vision is limited to shades of cream and brown. Their binocular vision is limited and they have poor depth perception. As poor as their vision is, it's fine for them because hedgehogs are nocturnal animals, emerging from their nests at night to forage for food.

Small Ears, Big Hearing
Don't feel bad for hedgehogs because their eyesight isn't very good; their other senses make up for this shortcoming. Hedgehogs may not have giant ears, but their ears are positioned for picking up important sounds. Their ears are also sensitive, allowing them to pick up high tones. According to Louisiana State University, hedgehogs have a hearing frequency range between 250 and 45,000 Hz. They can't hear low-pitched sounds as well as humans can, who can hear down to 64 Hz, but it's much higher than the human range of 23,000 Hz.

Use Your Ears
Good hearing is necessary for helping hedgehogs find their food. Their ability to hear high frequencies means they can hear prey as well as potential predators. Unfamiliar or loud noises prompt hedgehogs to take a defensive posture, ducking their heads. As well, good hearing helps hedgehogs orient themselves as they take on tasks such as crossing roads. If they hear something of interest, they'll stand very still to ensure they can hear even better, as their spines rustle and make distracting noise when they walk.

The Nose Knows
As good as hedgehog hearing is, it's only their second most valuable sense. Their sense of smell is their most important and used sense. Their sharp noses sniff out supper as well as intruders, picking up scents in the breeze. These guys are always sniffing as they walk, able to pick up the scent of dinner under as much as an inch of soil. They also can detect other hedgehogs by scent.