Ultrasonic waves are sound waves with frequencies higher than the upper audible limit of human hearing. They have various applications including medical imaging, industrial inspection, and cleaning. Infrasonic waves are sound waves with frequencies lower than 20 Hz which is the lower limit of human hearing. While infrasound is not audible, it can be detected by humans and cause physical effects at high intensities. It has military and biological applications such as infrasonic weapons and communication between some animals.

2. • 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.

3. Applications::
1.Engineering
Detection of flaws in metals (Non
Destructive Testing –NDT)

5. It is the most cheap technique
employed for cleaning various parts
of the machine, electronic
assembles, armatures, watches etc.,
which cannot be easily cleaned by
other methods.

6. 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.
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7. 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.

8. • 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.

9. Ultrasonic waves are used for studying the blood flow by
measuring the change in their frequency produced due to
Doppler’s effect.

11.  Scientists often use in research, for instant to break up high
molecular weight polymers, thus creating new plastic materials.
 Indeed, ultrasound also makes it possible to determine the
molecular weight of liquid polymers, and to conduct other forms
of investigation on the physical properties of materials.
 Ultrasonic can also speed up certain chemical reactions. Hence
it has gained application in agriculture, that seeds subjected to
ultrasound may germinate more rapidly and produce higher
yields.

12. 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.

13. 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.

16. • 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.

17. " . 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)

18. 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.