Infrasound and ultrasound they are qualities of sound waves related to its height or frequency. Human beings are only able to hear sounds that extend between the frequencies of 20Hz and 20.000Hz. Thus, any sounds with a frequency lower than this range are called infrasounds, while those sounds with frequencies higher than 20.000Hz are called ultrasounds.
Lookalso:What are sound waves?
What is infrasound?
Infrasound is the name given to sound waves whose frequency is found bellow of the human audible spectrum, that is, it is the sound that presents frequency less than 20 Hz. Infrasound is, therefore, a low-frequency sound that cannot be heard, but which, under certain conditions, can be perceived as vibration, through the tact.
Lookalso: How does human hearing work
You infrasounds they can be emitted by natural phenomena, such as earthquakes, avalanches, lightning, among others. Some animals are able to communicate through infrasound. This is the case with whales, hippos, rhinos and giraffes, for example. Due to its low frequency, the
wave-length From infrasounds é very large,and, therefore, this type of sound has great capacity for outline objects and propagate per great distances without major power dissipations. Whales, for example, can communicate ultrasonically from thousands of miles apart.
Whales can communicate with infrasound even thousands of kilometers away from each other.
You infrasounds can also be produced artificially through explosions, in engines powered by diesel oil, in turbineswind and in some speakers that emit soundsbass. Around the world, there are several infrasound detectors that monitor the detonation of nuclear warheads, through software that are able to distinguish the signal from this type of explosion from the signals coming from the Earth's seismic activity, for example.
Wind turbines produce very intense, low-frequency noise.
What is ultrasound?
ultrasound is the name given to sound waves with frequencies higher than 20.000Hz and therefore inaudible to human beings. Ultrasound is used in several areas of knowledge and for various investigative purposes. In medicine, the ultrasound are used as a non-invasive imaging able to reveal details of internal organ structures; in the materials industry, ultrasound is used to reveal microscopic flaws in metal or concrete structures; in geology, ultrasound is used to analyze soil and rocks; in addition, ultrasound can be used to facilitate or even speed up some chemical reactions.
Lookalso:Tips to improve your hearing
Some animals are able to hear ultrasound perfectly well, such as bats, which, in addition to hearing and producing them, use them as a kind of radar (the process is called echolocation) able to detect their prey. The sounds produced by bats can vary between 100 kHz and 200kHz.
sound frequency
The frequency of a sound wave measures how many times the wave oscillates each second. In SI, the frequency is measured in Hz, but it is common to come across multiples of this unit, such as the kHz (kiloHertz – 103 Hz), the MHz (megaHertz – 106 Hz), the GHz (gigaHertz - 109 Hz) etc.
The frequency of a sound wave can be calculated by its number of oscillations per second, but it can also be determined by the ratio of its velocityinpropagation (v) by your lengthinwave (λ), note:
For example, a sound wave whose wavelength is 10cm (0.10 m) and propagation speed is 340m/s will have a frequency equal to 3400Hz (3.4 kHz):
ultrasound exam
The ultrasound exam is a very popular exam for its agility, effectiveness, safety and low cost. Ultrasonography can provide details of the internal structures of organs, fetuses and even blood circulation in real time and without causing tissue damage. The ultrasound device emits very high frequency sounds, between 2MHz and 10MHz (megaHertz), which are produced by a transducer. The transducer consists of a small piezoelectric crystal, able to produce a small electric current when experiencing a vibration. Thus, when the transducer crystal captures a echo from a sound wave that has been reflected by some structure under the skin, a small electrical signal is produced and translated by the computer into an image.
Despite being a safe, non-ionizing test, ultrasound can cause small biological effects. During their propagation in the human body, ultrasonic waves transfer energy to tissues, heating them and producing free radicals, which can damage the genetic code of cells.
auditory spectrum
Human hearing has audibility limits for certain sound frequencies. On average, humans are able to hear well between the frequencies of 20Hz and 20.000Hz. Check the table below that shows the ranges of the audible spectrum of some animals:
Animal |
hearing spectrum |
Human |
20 Hz to 20,000 Hz |
Dolphin |
150 Hz to 150,000 Hz |
Puppy |
15 Hz to 50,000 Hz |
Cat |
60 Hz to 65,000 Hz |
Bat |
1000 Hz to 120,000 Hz |
As dogs are able to hear lower sounds, up to 15 Hz, some of them are trained to warn humans of the arrival of earthquakes, for example. This type of natural event produces low frequency sounds that are inaudible to humans.
By Me. Rafael Helerbrock
Source: Brazil School - https://brasilescola.uol.com.br/fisica/o-infrasom-ultrasom.htm