Bats
We have developed systems that use echolocation. Sonar, which means “sound navigation and ranging,” is echolocation in water and is used by boats, while radar is used in the air. These are advanced systems developed by engineers. Some animals are born with such an ability, which also required an engineer! Dolphins, whales, and bats are the most well-known, in addition to some rarer bird species. Bats fly at night using echolocation. They emit high-frequency sound waves that the human ear cannot hear. When these ultrasonic waves hit solid objects such as trees, buildings, or insects, they bounce back as an echo that provides the bat with information about its surroundings. A specialized larynx produces an intense and high-frequency sound. The sound is modified by the oral cavity and emitted through the mouth, and in some species also through the nose. Ultrasound weakens faster, so the range is quite short. Therefore, it is less suitable for studying the terrain and more suitable for catching insects. Ultrasound is well-suited for observing smaller objects. They can locate insects at a distance of 30 meters, while the effective distance for catching insects is a few meters. This makes it possible to catch insects in complete darkness. The bat “sees” with ultrasonic hearing! The time it takes for the sound to return provides information about the distance to the object. The bat also receives information about the insect’s size and speed, and which direction it is flying. This is necessary for a successful catch.
When bats fly in swarms, each bat can recognize its own sound among thousands of other sounds from other bats. The sound is sent in stages so that the emitted sound is not confused with the echo of the previous sound. The sound lasts only a few milliseconds. Since ultrasound weakens quickly, the sound must be quite loud. We all know that too loud sound is harmful to hearing. This also applies to bats! It is so wisely arranged that at the moment the sound is produced, a muscle pulls away the innermost bone in the middle ear, the stapes, so that the sound does not reach the bat’s inner ear, which is protected. The reflected sound is much weaker than the emitted sound, so it is a well-developed system that is capable of receiving and interpreting the echo. The bat’s brain makes the necessary calculations in an ultra-short time, and this information must be processed before the next sound signal is sent out. Knowledge of the speed of sound is a necessary factor. Researchers let bats fly in an atmosphere where they reduced the amount of nitrogen, which was replaced with helium. This increased the speed of sound by 15%. The study showed that the bat seems to have an innate knowledge of the speed of sound, which seems to be programmed into the bat’s brain. It seems that the researchers did not like this result of the study! In the literature, it is stated that bats evolved through evolution. Fossils have been found that are said to be 54 million years old. The special thing is that the fossil is identical to living bats and seems to be what is called a “living fossil.”
Dolphins
Dolphins are among the most intelligent animals. They can be trained to perform special stunts for the enjoyment of the audience. Dolphins communicate by sound, but they do not have a language. They identify themselves by a signature signal that is so clear that researchers can identify them by looking at a sonogram of the sound. Newborns are taught to recognize their own mother by the sound she emits so that she is easy to find for the calf when it needs milk. The calf develops its own signature signal within the first month, which shows how important it is.
Dolphins have a developed system for echolocation. They emit sound waves that are reflected by objects the sound hits. This provides the dolphin with information useful for navigation, hunting for food, protection against predators, in the dark, and when visibility in the water is poor. It starts with the dolphin opening its blowhole and inhaling air into the lungs, while the nasal cavity fills with air. The dolphin does not have vocal cords. The sound is produced in the nasal passage when air flows past during exhalation and creates vibrations in the tissue. In the roof of the nasal passage, there is a structure called the dorsal bursa, where there are special – phonic – lips that produce sound when the air passes. By adjusting these lips, sounds of different frequencies can be produced. Lower frequencies are used for social communication, while high-frequency sound is used for echolocation.
Sound is emitted as a click that lasts from 50 to 125 microseconds. The sound passes through a structure called the melon, which is located in the forehead. The melon functions as a sound lens and is a sophisticated structure designed to focus sound waves into a beam that can be directed as the dolphin wishes. The melon consists of many different types of fats (lipids) that form layers of fat. This fat must be arranged in a special way for the sound waves to be focused into a beam. Each lipid is unique and different from ordinary fat and is often called acoustic fat. They are produced through a complex chemical process that requires several enzymes.Naturalism has no explanation for how this fatty tissue came to be, nor how it is able to produce focused sound.
When the dolphin finds a specific fish it aims to catch as food, it will usually keep the sound beam focused on this fish until it has it in its mouth. The high-frequency sound can have a frequency between 40 and 130 kHz. The receiver for the reflected sound is located in the lower jaw, which functions similarly to the outer ear in humans. In the rear part of the lower jaw, there is a fat pad that functions as an acoustic window, absorbing the reflected sound. Additionally, the teeth function as antennas that have a resonance that amplifies the sound signals. So it is a very complex receiver system in operation. The sound is transmitted to the inner ear, which sends the sound as a nerve signal to the brain, where the information is processed within fractions of a second, allowing the dolphin to make the necessary adjustments, for example, to catch a fish.
Whales have the same principle for echolocation as dolphins and use different types of sounds to communicate with other whales. They are social animals that live in groups. Communication is therefore important. There are also whale species that emit sounds that can be characterized as songs! The whale can produce the loudest sound in the animal kingdom, which drowns out even a jet engine. The sound has a large range, up to 8000 kilometers.
From the book of prof emeritus Kjell J. Tveter “So much to wonder about”
