Sound waves are part of our daily lives, as they are used in communication through speech and music. The ability we have to produce different types of sounds, using the vocal tract, combined with our mental capacity, allowed us to create a complex and efficient spoken language.
Thus, we say that the ability to transmit information through sound waves has made human beings develop both skills and instruments for the production of sounds. As we said, audible sounds are used for communication, whereas inaudible sounds have several applications in engineering, basic sciences and medicine, mainly in the form of ultrasound.
pulses of ultrasound they are generated by special crystals (such as pure quartz), which can vibrate when a convenient electrical current flows through it. In this way, it is possible to generate ultrasound pulses with frequencies of several MHz and lasting only a few millionths of a second.
Ultrasound waves propagate in the same way as audible sound waves. They undergo all the phenomena of reflection, refraction, diffraction and interference, like all waves.
By sending an ultrasound pulse into a material, it will be partially reflected by the find any discontinuities in the medium, such as a change in density or defects in the medium itself. material. If we send an ultrasound wave into an iron bar that has an internal failure due to a manufacturing defect, this wave will be partially reflected in the discontinuity and can be detected by a receiver.
By measuring the time between the beginning of the pulse and its return (echo), the depth and dimension of the fault can be determined. This measurement system is industrially used to detect cracks in steel pipes, parts of engines and structures of buildings and bridges.
In medicine, ultrasound is widely used for diagnosing heart disease and preventive exams in pregnant women. With the help of a computer, the system transmits ultrasound waves in all directions and detects the signal reflected in different types of tissues and bones. In this way, it is possible to obtain the image of a fetus. New techniques can record three-dimensional images of the baby from several images obtained through ultrasound.
By Domitiano Marques
Graduated in Physics
