APPLICATIONS OF ULTRASOUND

&WORKING AND STRUCTURE OF THE HUMAN

EAR

What Are Ultrasounds ?Ultrasonic waves are high-frequency sound waves that cannot be heard or sensed by humans. These are so energetic that they can penetrate human muscles. These ultrasonic waves can be used for various practical purposes.

Applications Of Ultrasounds Include :

Ultrasound is generally used to clean parts located in hard-to-reach places, for example, spiral tube, odd shaped parts, electronic components etc. Objects to be cleaned are placed in a cleaning solution and ultrasonic waves are sent into the solution. Due to the high frequency, the particles of dust, grease and dirt get detached and drop out. The objects thus get thoroughly cleaned.

Ultrasounds can be used to detect cracks and flaws in metal blocks. Metallic components are generally used in construction of big structures like buildings, bridges, machines and also scientific equipments. The cracks or holes inside the metal blocks, which are invisible from outside reduces the strength of the structure. Ultrasonic waves are allowed to pass through the metal blocks and detectors are used to detect the transmitted waves. If there is even a small defect, the ultrasound gets reflected back indicating the presence of the flaw or detect.

• Ultrasonic waves are made to reflect from various parts of the heart and form the image of the heart. This technique is called ‘echocardiography’.

• Ultrasound scanner is an instrument which uses ultrasonic waves for getting images of internal organs of the human body. A doctor may image the patient’s organs such ass the liver, gall bladder, uterus, kidney, etc. It helps the doctor to detect abnormalities, such as stones in the gall bladder and kidney or tumours in different organs. In this technique the ultrasonic waves travel through the tissues of the body and get reflected from a region where there is a change of tissue density. These waves are then converted into electrical signals that are used to generate images of the organ. These images are then displayed on a monitor or printed on a film. This technique is called ‘ultrasonography ‘.

• Ultrasound may be employed to break small ‘stones’ formed in the kidneys into fine grains. These grains later get flushed out with urine.

SONAR

The acronym SONAR stands for Sound Navigation And Ranging. Sonar is an acoustic device used to measure the depth, direction, and speed of under – water objects such as submarines and ship wrecks with the help of ultra sounds. It is also used to measure the depth of seas and oceans.

A beam of ultrasonic sound is produced and transmitted by the transducer (It is a device that produces ultrasonic sounds) of a SONAR, which travels through sea water. The echo produced by the reflection of this ultrasonic sound is detected and recorded by the detector, which is converted into electrical signals. The distance (d) of the under – water object is calculated from the time (t) taken by the echo to return with speed (v) is given by 2d = v x t. This method of measuring distance is also known as ‘echo – ranging’.

ULTRASOUND AND ANIMALS Bats

Bats use a variety of ultrasonic ranging (echolocation) techniques to detect their prey. They can detect frequencies beyond 100 kHz, possibly up to 200 kHz.

Insects Many insects have good ultrasonic

hearing and most of these are nocturnal insects listening for echolocating bats. This includes many groups of moths, beetles, praying mantids and lacewings. Upon hearing a bat the insects will make evasive manoeuvres to escape being caught by the bat.Ultrasonic frequencies trigger a reflex action in the noctuid moth that cause it to drop a few inches in its flight to evade attack.

Tiger moths also emit clicks which may disturb bats' echolocation,but may also in other cases evade being eaten by advertising the fact that they are poisonous by emitting sound.

Ultrasound generator/speaker systems are sold with claims that they frighten away rodents and insects, but there is no scientific evidence that the devices work.

• Dolphins and whales It is well known that toothed whales (Odontocetes), including

dolphins can hear ultrasound and use ultrasonic sounds in their navigational system (biosonar) to orient and capture prey.Porpoises have the highest known upper hearing limit, at around 160 kHz.

• In 2011 researchers in the United States and Great Britain, using a Cyma Scope, an instrument which produces visible patterns from sound, found that part of dolphin communication consists of receiving and transmitting sound pictures. It is almost certain that to some extent this ability is shared by the entire dolphin family.

• Fish Several types of fish can detect ultrasound. In the order

Clupeiformes, members of the subfamily Alosinae (shad), have been shown to be able to detect sounds up to 180 kHz, while the other subfamilies (e.g. herrings) can hear only up to 4 kHz.

Dogs Dogs can hear sound at higher frequencies than humans can. A dog whistle exploits this by emitting a high frequency sound to call to a dog. Many dog whistles emit sound in the upper audible range of humans, but some, such as the silent whistle, emit ultrasound at a frequency in the range 18–22 kHz.

STRUCTURE OF HUMAN EARDifferent sounds produced in our surroundings are collected by pinna that sends these sounds to the ear drum via the ear canal. The ear drum starts vibrating back and forth rapidly when the sound waves fall on it. The vibrating eardrum sets the small bone hammer into vibration. The vibrations are passed from the hammer to the second bone anvil, and finally to the third bone stirrup. The vibrating stirrup strikes on the membrane of the oval window and passes its vibration to the liquid in the cochlea. This produces electrical impulses in nerve cells. The auditory nerve carries these electrical impulses to the brain. These electrical impulses are interpreted by the brain as sound and we get a sensation of hearing.

Made By -Ananya Nair Adveta Jasrotia