ultrasound is the name given to sound waves whose frequencies are beyond the limit of human hearing. Normally, human beings are able to hear sounds whose frequencies vary between 20Hz and 20 thousandHz. This range is called the audible spectrum frequencies. Ultrasound is also the informal name given to the ultrasound exam, used for the anatomical investigation of organic tissues in real time.
Ultrasound in Physics
Sound is classified as a wave of naturemechanics it's from propagationlongitudinal. It is a vibration capable of propagating in the air and in different media through the oscillation of molecules, generating regions of compression and rarefaction. Also, during its propagation, the sound transportsonlyenergy.
Lookalso: Classification of sound waves
The sounds have some qualitiesphysiological that differentiate them from each other. They are: frequency, intensity and timbre.
The frequency of a sound is defined by the numberinoscillations that it generates in the medium through which it propagates every second. Frequency is measured in Hz. Sounds whose frequency is greater than 20 thousand Hz are
inaudible by human beings and, therefore, they are called ultrasound.The sound intensity measures the potencypersubwaysquare Of the sound. This property is measured in decibels (dB).
O timbresonorous it concerns the shape of the waves and is defined according to the source producing the sounds. Each sound source has its own characteristic timbre.
Lookalso: Intensity, timbre and pitch of sound
Humans are incapable of hearing any frequency of sound. Most human beings can perceive sounds that range from 20 Hz to 20 thousand Hz (some authors adopt 16 Hz as the lower limit for audible sounds).
Some animals, such as cats, dogs, dolphins and bats, have the ability to hear sounds at frequencies much higher or lower than those perceived by humans. Look at the table below:
Animal |
Minimum heard frequency (Hz) |
Maximum heard frequency (Hz) |
Human |
20 |
20 000 |
Elephant |
20 |
10 000 |
Dog |
15 |
45 000 |
Whale |
40 |
80 000 |
Bat |
1000 |
160 000 |
Lookalso: human hearing
ultrasound exam
Ultrasound is the popular name given to the examination of ultrasound. It is an exam that captures real-time images of the interior of the human body through the reflection and of the absorption of high frequency sound waves.
Compared to other medical tests, ultrasound has several advantages. Among them, we can highlight the acquisition of images in timereal, lowcost it's big mobility. Also, it's an exam non-invasive and poses no risk to the patient's health.
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Despite the large amount of positive points, the ultrasound exam also has its negative points. Among them, we can highlight the need for patient cooperation and preparation, a reduced field of vision in relation to to other exams, poor image quality, difficulty in obtaining images in regions with bones or air.
Ultrasound tests are widely used to determine the sex of babies from the thirteenth week of gestation onwards.
Lookalso: Five Things You Need to Know About Sound Waves
How does the ultrasound exam work?
The ultrasound exam is fast and painless. In general, ultrasound devices use very high frequencies, between 2 MHz and 14 MHz. During the procedure, audible pulses are emitted that are absorbed, reflected and refracted at different speeds according to the type of fabric: skin, bones,fat, blood, etc. The ultrasound device captures the echo formed by the pulses and produces a computerized image of the internal relief of the organs by calculating the small differenceintime between the audible pulses incidents and reflected.
Check below the operating steps of an ultrasound exam:
The ultrasound machine produces very high frequency sound pulses directed to a certain region of the human body.
Sound waves propagate inside the body until they reach the boundaries between different tissues, such as skin and fat, muscles and bones, for example.
A portion of the sound waves is reflected at the tissue boundary, returning to the emitting probe, which records the reflected wave. The other parts of the waves continue to propagate through the tissues.
The computer connected to the emitting probe calculates the distance covered by the reflected wave using the speed of sound inside the human body (although it varies a little for different tissues, this speed is around 1540 m/s) and the time needed to detect the sound pulse reflected.
Millions of sound pulses are emitted and reflected every second, forming, in real time, a two-dimensional image of the interior of the human body.
Lookalso: What is the speed of sound?
By Me. Rafael Helerbrock
Would you like to reference this text in a school or academic work? Look:
HELERBROCK, Rafael. "What is ultrasound?"; Brazil School. Available in: https://brasilescola.uol.com.br/o-que-e/fisica/o-que-e-ultrassom.htm. Accessed on June 28, 2021.
