First of all my respectful greetings to the entire academic community of Hive.blog, this time my dear readers we continue to relate to the wonderful phenomenon of sound in its various forms of frequency, and thus, wavelengths, therefore, we will analyze ultrasound in general.

Introduction

It is no secret that the human being lives immersed in a species-time, where innumerable natural phenomena develop and from which we have had the remarkable ability to learn from them, and for this we have undoubtedly used fundamental tools for the extraction, application and expansion of all kinds of knowledge of our mother nature.

In relation to the above, we must always highlight the tireless task of the essential fields of science, technology and, of course, education, that is, a fundamental trinomial that has allowed us to exponentially increase our intellectual capacity, and with it, our survival in this complex universe.

In addition, we have also been able to self-grant ourselves a great amount of well-being due to the use of the understanding of such natural phenomena, thus raising our quality of life, of course, being attentive to the rational use of such knowledge, about technology, but we will talk about that in another opportunity.

We could think my dear readers that due to our intrinsic relationship with our nature, sometimes we do not realize the action of certain applications based on phenomena such as sound, which is why in this opportunity we will link in a general way with an important spectral fraction of this phenomenon such as ultrasound.

Let us remember that all types of sound waves, whether we can perceive them or not, originate through some type of vibration, therefore, without the vibration of the component particles of an object or body, there would not exist those longitudinal pressure waves that manage to disturb a certain material medium such as air and stimulate our natural auditory system such as our ears.

Let us remember that in our journey along the path of learning about sound we have analyzed essential aspects of sound such as its generation, propagation, reflection, absorption, transmission, diffraction, refraction, acoustic spectrum, infrasound and now ultrasound, all of this with the purpose of educating us in a general way about such an important phenomenon.

Ultrasound

Ultrasound represents a fraction of our acoustic spectrum that we cannot perceive, that is, it is beyond the reach of our ears, but, for this we must remember what is the audible range for the human being and it is between 20 to 20,000 Hz (Hertz), therefore this range is our reference for the determination of the different sound waves generated in our environment.

That is why those vibrations that generate sound waves below 20 Hz are known as infrasound because they are below our minimum hearing level, and this time we go to the other end of the acoustic spectrum to relate to those sound waves that exceed 20,000 Hz, and this places them outside our hearing range.

Therefore, these sound wavelengths generate a higher frequency than those belonging to our acoustic reference described above (our audible range), that is why we know them as ultrasound, therefore, it is necessary to visualize our acoustic spectrum, but now including the spectral fraction of ultrasound as you can see in Figure 1 below.

_{Figure 1. Acoustic spectrum according to frequency}

Although humans do not have the natural ability to perceive ultrasound, it is important to note that there are other living species that do, such as bats, which are able to hunt their prey in the dark using a phenomenon called echolocation, and can thus explore their environment by emitting ultrasonic sound waves that bounce off any body or object around them and return to them in the form of images.

Another living species that uses ultrasound are dolphins for the same purpose, as do giraffes, which communicate with ultrasound, as shown in the following figure 2.

_{Figure 2. Some animals that emit ultrasound}

This makes us express that although we cannot perceive ultrasound, it is constantly produced in our environment and is part of essential natural events of great importance for many living species of our planet.

In the next installment we will be relating to some artificial applications of ultrasound and this thanks to the inventive capacity of man through science-technology, which has allowed us to make great advances in our development in all senses.

Conclusion

At every moment of our existence countless phenomena take place or develop in our environment such as ultrasound, and thanks to our remarkable scientific and technological progress we have been able to detect it and learn from it, and also how it is used by some living species that cohabit with us on this planet.

In this way we were able to broaden our acoustic spectrum to include the spectral fraction of ultrasound and that it is generated naturally, and that artificially has given us many benefits especially in relation to our health, but this is what we will be talking about in the next installment.

Until another installment, my dear Hive.blog readers.