In nature, all kinds of sound waves and signals are endless, filling the whole world, and most of the signals are inaudible to humans, but animals can hear them. The reason is that they have to mention their magical ears.
Can hear the sound that humans can’t hear
Scientists have found that the sounds that animals use are less than 10% that humans can hear. Human ears can hear vibration waves with frequencies between 20 and 20,000 Hz, which are deaf to other frequencies. However, different animals hear different ranges of sound frequencies. For example, cats can distinguish between 30 and 4 500 Hz. The highest limit of hearing is 60,000 Hz. The highest limit of hearing for bears and macaques. It is 80 000 Hz, the highest limit of guinea pig hearing is 100 000 Hz, the hearing range of rats and baboons can reach 90 000 ~ 120 000 Hz, and the maximum limit of hearing of squirrels is even 250,000 Hz.
A vibration wave with a frequency below 20 Hz is called an infrasound wave. Although the human ear can’t hear them, they can feel them with their own bodies, which can cause some unreasonable uneasiness, and even make people feel uncomfortable. However, the use of infrasound for communication is a good thing for some animals, because the low-pitched infrasound can spread through the ground through the ground, the source of the sound can not be identified, so it is not easy to be discovered by the predator. Infrasound waves also have the advantage of extremely long propagation distances. Infrasonic waves with frequencies below 1 Hz can be transmitted thousands to even thousands of kilometers away. Therefore, some male animals often use the hoof to step on the ground and issue orders by issuing infrasound waves. The largest terrestrial animal, the elephants, also use the secondary sound waves to communicate with each other. Some marine life can even use the infrasound of a certain frequency to stun and kill prey.
Ultrasound with a frequency above 20,000 Hz is another type of sound that is inaudible to human ears, but is widely used by birds such as oil mites, swiftlets, bats, sea lions and cetaceans in mammals, such as dolphins and Seals can make and hear sounds up to 180,000 Hz underwater. However, although the upper limit of seals outside the water is only about 22 000 Hz, since the sound travels in water five times faster than in the air, and because of other differences, mammals have different hearing in the water and in the air. The high frequency limits in these two media are also difficult to compare.
Animal ears have their own magic
The outer ear of a mammal includes the auricle and the external auditory canal. The auricle is unique to mammals and has elastic cartilage support, making it a highly sophisticated and sensitive sound collection device. However, the structure of the various types of mammalian auricles living in different environments is very different, thus forming a variety of “ears.”
The most striking thing is undoubtedly the huge “eyes”. Large ears can increase the area where sound is collected, so that the sound is heard more clearly. In general, mammals that are nocturnal or open in open areas are well-developed, such as bats, rabbits, dogs, and ungulates. Some of these types of ears often have special concave pleats for better Accept sound waves. The aardvark living in Africa can accurately hear the sound of termites in trees or other objects. The monkeys living on the island of Madagascar can also hear the sounds of insect larvae that are drilled into the trunk, and then use the forelimbs very much. The thin middle finger dug up these larvae to eat. The large ears of squirrels that jump around in the woods also protect themselves from stab wounds.
The largest animal in the ear is the African elephant, which is about 2 meters in diameter and is very sensitive to hearing. Due to the large number of folds in the ear, the heat-dissipating surface is greatly increased, so it is more like two large-sized fan that regulates body temperature. In the hot summer, it is to constantly fan the two large ears to accelerate the flow of blood in the ear. To achieve the purpose of cooling and cooling, it can also drive away mosquitoes and parasites in the tropical jungle.
The long ears of the rabbit are also very famous. In addition to the hearing function, the body temperature can also be adjusted. When standing up, it can dissipate heat. When it is close to the back, it can be kept warm. Interestingly, rabbits living in cold regions have much shorter ears than rabbits living in hot spots. The same result will be seen in groups such as wolves, foxes, and felines.
Many mammalian ear muscles are well developed, allowing the auricle to rotate freely, so that sounds in different directions can be collected more efficiently. The fox and the dog’s ears are like a megaphone. When they hear the sound, they raise their ears and turn the ear to the direction in which the sound is heard. Each ear can work independently and not with the other ear. The activity of the two ears is not uniform, thus providing the possibility to accurately determine where the sound source is. The ears of the feline can also be rotated in the direction of the sound, like a radar antenna, which can distinguish two similar sounds that are about 1 meter apart from 15 to 29 meters away.
As an auditory organ, even when animals are sleeping, their ears are still working, but the ear’s response to sound is not as sensitive as in the awake state. However, there is a “warning center” in the animal’s brain, which makes its hearing a reliable guardian, able to report danger to them in time, forcing the animal to wake up and take action. For example, when the koala bears sleeping, although the two big ears hang down with the head, but when the outside world moves, the ear will feel immediately, and it will wake up in an instant. When the cat is sleeping, it usually squeezes the ear under the forelegs, so that on the one hand, the ear is protected, on the other hand, the ear is attached to the ground, and once the sound is heard, the action can be taken immediately.
Due to the prominent out of the body, many animal ears are also beautiful decorative organs. For example, the two big ears of a koala bear full of dense hair, standing high on both sides of the head, look extraordinarily sultry. The panda’s ears are large and erect, with white edges on them. A pair of furry black ears of the giant panda erected above the head, becoming a part of its simple and elegant black and white fur, lively and lovely. The most interesting thing is that the tops of the two upright ears are covered with black pens, about 4 cm long, and there are also a few white hairs, much like the scorpions on the helmet of the military commander in the drama. Added a bit of majestic momentum.
Although the shape of the human ear is not as colorful as other mammals, it is also a pair of beautifully constructed organs. From an aesthetic point of view, the most beautiful ear size should be 1/3 of the hairline to the length of the jaw. However, in our country, there is a saying that “the ears are blessed.” In fact, other human organs have basically stopped growing in adulthood, but with the exception of the ear, they continue to grow throughout their lives, mainly in the length of the earlobe. It has also been suggested that the adipose tissue in the earlobe of the elderly is increased and the tissue is slackened, resulting in a corresponding increase in the length of the earlobe. Therefore, regardless of whether the ears are large or small at birth, when they reach old age, their ears are always larger, at least larger than when they are young. Therefore, the ears of longevity people are naturally larger and thicker.