• The word ultrasonic combines the Latin roots ultra, meaning ‘beyond’ and sonic, or sound.• The sound waves having frequencies above the audible range i.e. above 20000Hz are called

ultrasonic waves. • Generally these waves are called as high frequency waves.• The field of ultrasonics have applications for imaging, detection and navigation. • The broad sectors of society that regularly apply ultrasonic technology are the medical

community, industry, the military and private citizens.

Applications::

1.Engineering

Detection of flaws in metals (Non

Destructive Testing –NDT)

It is the most cheap techniqueemployed for cleaning various partsof the machine, electronicassembles, armatures, watches etc.,which cannot be easily cleaned byother methods.

The method consists of sending a powerful beam of ultrasonics in

the suspected direction in water.

By noting the time interval between the emission and receipt of

beam after reflection, the distance of the object can be easily

calculated.

The change in frequency of the echo signal due to the Dopper

effect helps to determine the velocity of the body and its direction.

2

tvd

1.Sonar is used in the location of

shipwrecks and submarines on the

bottom of the sea.

2.It is used for fish-finding

application .

3.It is used for seismic survey.

• Treating malignant tumors and other disorders, via a

process known as Focused Ultrasound Surgery (FUS)

or HIFU, High Intensity Focused Ultrasound.

• These procedures generally use lower frequencies than

medical diagnostic ultrasound (from 250kHz to

2000kHz), but significantly higher time-averaged

intensities.

Ultrasonic waves are used for studying the blood flow by

measuring the change in their frequency produced due to

Doppler’s effect.

Scientists often use in research, for instant to break up highmolecular weight polymers, thus creating new plastic materials.

Indeed, ultrasound also makes it possible to determine themolecular weight of liquid polymers, and to conduct other formsof investigation on the physical properties of materials.

Ultrasonic can also speed up certain chemical reactions. Henceit has gained application in agriculture, that seeds subjected toultrasound may germinate more rapidly and produce higheryields.

Infrasound, sometimes referred to as low-frequency sound, is

sound that is lower in frequency than 20 Hz (Hertz) or cycles

per second, the "normal" limit of human hearing. Hearing

becomes gradually less sensitive as frequency decreases, so for

humans to perceive infrasound, the sound pressure must be

sufficiently high. The ear is the primary organ for sensing

infrasound, but at higher intensities it is possible to feel

infrasound vibrations in various parts of the body.

Infrasonic wave: the waves of frequency less than 20Hz are known

as infrasonic waves. The infrasonic waves are produced by large

vibrating bodies. These waves are not audible to a human ear. For

example, infrasonic waves are produced by the vibration of the earth’s

surface during the earthquake. Some animals like elephants,

rhinoceroses and whales etc. also produce infrasonic waves.

Application of infrasonic waves: there are following applications of

infrasonic waves.

a Infrasonic waves are produced by large vibrating bodies.

b. Its frequency is less than 20 Hz.

• Depending on the pitch, infrasound can

cause physical pressure, fear,

disorientation, negative physical and

mental symptoms, explode matter,

incapacitate, and kill.

• For example, in World War II, Nazi

propaganda engineers used infrasound to

stir up anger in the large crowds that had

gathered to hear Hitler. The result was a

nation filled with anger and hatred.

" . High power, very low frequency waves

emitted from one to two meter antenna dishes. Results in blunt

object trauma from waves generated in front of the target.

Effects range from discomfort to death. A Russian device that

can propel a 10-herz sonic bullet the size of a baseball hundreds

of yards is thought to exist. Proposed fixed site defense. Also

known as sonic bullets." (Source - Glossary of Non-lethal

weapons Terms, edited by Robert Bunker)

It has been known that certain whiles are able to stun

their prey with powerful blasts of inaudible sounds, called

'gunshots,‘. Whales focus these powerful blasts at large

squid and other fish to paralyze and catch them. In some

instances, they have been known to burst their prey apart

by tonal projection alone.

These are found to be infrasonic waves.