We have eyes to look at the world around us. In addition, we have other senses to help us navigate through our day-to-day life.  We would have definitely come across various Applications of Ultrasound in our lives. Animals like elephants, dogs, and cows also make noises when they face any difficulty. But what about the animals that neither possess the gift of sight nor sound? How do animals like bats, beetles, or moths detect the presence of obstacles in their path, or how do they look for prey? By emitting ultrasounds.

We know that sound waves need a material medium to travel, and the human ear can only detect sound frequency within the audible range. For human beings, the audible range lies between \(20\;{\rm{Hz}}\) to \(20\;{\rm{kHz}}\), and it is different for every other living being. However, sounds that lie below and beyond this range are not audible to the human ear, and this is why ultrasounds emitted by bats or moths remain imperceivable to us. This is the most real-life application of ultrasound, and it helps them to navigate through the dark. Ultrasounds have become part and parcel of our life; from the medical industry to military applications, these are being employed everywhere. Let us learn more about ultrasounds and their applications.

Ultrasound

Ultrasounds are sound waves that have frequencies higher than the upper audible limit of the human ear. In simple words, an ultrasound is a sound with a frequency above \(20\;{\rm{kHz}}\) or \(20,000\;{\rm{Hz}}\) i.e., above the highest value of the audible frequency. Although ultrasound frequencies up to few gigahertz can be created, however, it is not possible for us to detect them. The physical properties of the ultrasound resemble a lot with the audible sound.

Animals like bats apply echolocation techniques based on ultrasounds to detect their prey. Animals like dogs and cats can also detect ultrasounds up to \(60 – 65\,{\rm{kHz}}\). The dog whistles which dog training professionals use emit ultrasounds of frequency within the range of \(23 – 45\,{\rm{kHz}}\).

The physical properties of ultrasound are similar to the ordinarily audible sound. To detect their prey, bats employ various ultrasonic ranging (echolocation) techniques, and because of this, they can detect frequencies as high as \(200\,{\rm{kHz}}\). Toothed whales like dolphins emit ultrasounds and use them to navigate through the sea and catch their prey. The scientific concept of ultrasounds is applied in medicine, communication, navigation, testing, cleaning, detection, ranging and mixing, etc.

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Applications of Ultrasounds

1. Detection of cracks:

Ultrasounds are used to detect cracks in the large metallic components used to construct large structures like bridges and buildings. Ultrasonic waves generated and displayed by them are interpreted by a trained professional, who uses analysis software to locate and classify flaws in the parts of these buildings.

2. Echocardiography:

Specialists perform echocardiography to check the well-being of a patient’s heart condition. In this process, ultrasonic waves are employed to get an image of the heart using the techniques of reflection and detection of ultrasounds from various parts.

3. Cleaning:

Parts like spiral tubes and several electronic components in big machines are tough to clean. Such devices employ ultrasonic waves for their cleaning purpose. The object to be cleaned is kept in the solution of suitable cleaning material, and ultrasonic waves are passed through this solution. Due to the generation of these high-frequency waves, the dirt and grease detach from the surface.

4. USID:

USID or Ultrasound Identification is a Real-Time Locating System (RTLS). It is a type of Indoor Positioning System (IPS) which, in real-time, tracks and identifies the location of objects automatically. In this technology, inexpensive nodes (badges/tags) are attached to or implanted in objects and devices. The ultrasound signal transmitted from these devices is used to communicate their location to microphone sensors.

5. Lithotripsy:

Initially, people who had kidney stones had to undergo major operations to get them removed but using ultrasonic waves, the kidney stones can be broken down non-evasively without any unwanted surgeries. Thus, in this method, high-energy waves pass through the body without causing any major injury and break the stones into dust or smaller pieces. These pieces can then be removed from the body through the urinary tract.

6. Pest control:

Many animals can detect the sounds that lie in the human ultrasonic frequency range. In fact, it was observed that roaches and rodents are sensitive towards frequencies in the range of  \(40\) kilohertz. This is why “pest controllers” were manufactured that emit loud sounds in that frequency range to drive the pests away. Although the results have not been promising, developments are underway.

7. Ultrasonography:

Ultrasonic images are called sonograms. Medical ultrasounds that are usually done in hospitals are diagnostic imaging techniques based on ultrasonic imaging. It helps to get an image of internal body structures such as muscles, joints, and internal organs and detect the problem area. It is done by sending pulses of ultrasound to the tissue with the help of a probe. Each sound on striking a tissue reflects, and the sounds reflecting different tissues reflect at varying angles, thereby helping us differentiate them. These echoes of sound generated from the tissues are recorded and displayed in images for a specialist to check.

8. Sound Navigation and Ranging:

SONAR was designed to help in the navigation, detection, and communication under the water’s surface. In this technique, pulses of sound or ultrasound are sent out, and the time taken by the pulses to reflect off a distant object and return to the source is measured. Thus, with the help of SONAR, the precise location of that object can be ascertained, and its motion effectively is tracked. It helps locate and track lost ships or aircraft wrecks, submarines underwater, and explosive mines below the water’s surface.

9. Echolocation:

The process in which sound waves and echoes are used to determine objects in space is called echolocation. Bats employ echolocation to navigate in their surroundings and locate their food in the dark. Bats emit sound waves that lie in the ultrasound frequency range from their mouth and nose. These sound waves hit the objects around them and reflect, producing echoes. The bats then detect these echoes; it helps them judge the object’s size, shape, and distance. These days ultrasonic echolocation is being widely used in traffic management applications and for sorting and counting objects in an assembly line.

10. Ultrasonic Flowmeter:

Ultrasonic flowmeters use the technique in which the reflection of ultrasound from a flowing liquid causes a Doppler shift that is calibrated to provide the required flow rate of the liquid. This method is often applied to maintain blood flow in arteries.

11. Therapy:

Ultrasound offers various therapeutic applications, which can be very beneficial when used with proper dosage.  The high power provided by ultrasound is used to break up hard deposits or tissue. This helps to accelerate the effect of drugs in the required area, assist in measuring tissue’s elastic properties. Ultrasounds are often employed to sort cells or small particles for research.

12. Ultrasonography:

Ultrasounds are used to visualize the fetuses during routine prenatal care. Ultrasonography performed on pregnant women is used to check the child’s health and growth in the mother’s womb.

13. UIT

Ultrasonic impact treatment is used to enhance the mechanical and physical properties of metals using ultrasounds. It is a metallurgical process. In this technique, ultrasonic energy is applied to a metal object. Such treatment can lead to controlled residual compressive stress, refinement of grains, and reduction in grain size too. UIT has also been used for addressing stress corrosion cracking, corrosion fatigue, and related issues.

14. Ultrasonic sensors:

Sensors based on ultrasound are used as automatic door openers because these can cover a wide area from a single point. Ultrasonic sensors detect a person’s footsteps and open the door. Ultrasonic sensors are also useful in detecting intruders, thieves, and burglars. Ultrasounds are used for developing non-contact sensors that can strike the target from a distance and are used for various military and medical applications.

Summary

Ultrasounds are sound waves that have frequencies higher than the upper audible limit of the human ear. In simple words, an ultrasound is a sound with a frequency above \(20\,{\rm{kHz}}\) or \(20,000\;{\rm{Hz}}\) i.e., above the highest value of the audible frequency. The scientific concept of ultrasounds is applied in medicine, communication, navigation, testing, cleaning, detection, ranging and mixing, etc.

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Frequently Asked Questions

Q.1. What is ultrasound?
Ans: An ultrasound is a sound that has a frequency higher than \(20\,{\rm{kHz}}\). These are the sound waves with frequencies higher than the upper audible range of humans.

Q.2. Name the process by which bats detect their food.
Ans: Bats detect their food by the technique of echolocation.

Q.3. Write a few uses of ultrasounds.
Ans: Ultrasounds are used for:
a. Non-evasive cleaning
b. Detecting cracks in large buildings
c. Imaging of internal organs
d. SONAR

Q.4. What is echolocation?
Ans: Echolocation is the technique of the location of objects by reflected sound, particularly that used by animals such as dolphins and bats.

Q.5. Can humans hear ultrasounds?
Ans: No, the human ear can not detect ultrasounds.