Thesis: Sound waves are able to carry vibrations through a medium which results in the transfer of the energy collected in the vibrations. Transverse waves are vibrations which are at right angles to the wave’s direction of travel whereas longitudinal waves are vibrations along the line of wave’s direction of travel. These waves have a quantifiable speed, wavelength and frequency. Owing to these properties, sound waves have scores of uses.

Introduction: Human ear is capable of hearing sounds with frequencies of about 30Hz – 20 kHz. Sound waves are able to travel best through rigid solids rather than through liquids and gases. However, human ears have got accustomed to sound waves passing through air, so are able to hear various things. The loudness of the sound is based on the incoming waves’ amplitude whereas the pitch of the sound is based on the incoming waves’ frequency. Musical instruments work by building up regular vibrations like in the case of strings, skins, tubes of air which results in the surrounding air vibrating with the same pattern causing melodious music. Analysis: Usually sound is absorbed by various objects. However, in some cases, it is reflected which more commonly called as echo. When sound strikes soft materials, it is absorbed. Such materials that absorb most of the energy of sound waves are called sound insulators. This property of the sound is beneficial to geologists to locate oil reservoirs. It also helps in tracking earthquakes and to find out how earthquakes travel through different kinds of rocks and magma.

Ultrasonic waves are those sound waves which are of every high frequency with short wavelengths. Though human ear cannot feel or recognize it, it has many uses. Sonar which is an acronym for Sound Navigation Ranging is used to find the depth of underwater as well as for oceanic explorations. The sonar devices are capable of sending short pulses of ultrasonic waves through the water. When these waves collide with the sea floor, some of them are absorbed. However, some of the waves are reflected back to the ship in the form of an echo which is detected through receivers helping researchers to get information like the exact depth of the ocean, etc. It is also used for military purposes especially in submarines. Ultrasonic waves are also beneficial for cleaning intrinsic jewelry, parts of machineries as well as electronic components. Some innovative ideas are to clean dirt from items in the bath with the usage of ultrasonic waves. Another most common usage of ultrasonic waves is for medical purposes which are predominantly known as Ultrasound. This is used to remove stones from the kidney. The usage of ultrasound replaces complicated operations and enables doctors to break down the stones in the kidney into small pieces without causing any problem to the other parts of the body.

Ultrasound is also able to find out what is happening inside the body. The reflected waves of the sound are administered into a computer which enables the formation of pictures called a `Sonagram or medical scanning’. Ultrasound are able to penetrate the body easily, however, some is reflected off each tissue boundary. The bounced back pulses are used to build up a picture of inside the body. [Other Uses Of Sound Waves, 2004]

This process is most common in identifying the position as well as the development of fetus inside the stomach of pregnant women and avoids any subsequent complications. Ultrasound also helps in located tumors or gallstones inside the body. This process is less damaging than other penetrating waves like the x-rays which uses the ultraviolet rays.

Apart from this is the echocardiography which again uses ultrasound waves produced by a probe which is placed on the chest of a human body which in turn travels through the body. This sound waves are harmless and when inside the body, reflect from various body tissues and comes back to the transducer with a different frequency of sound waves which are formed than those originally sent into the body. Similar to a medical scanner, the echocardiogram machine receives and interprets these sound waves and produces pictures of the inside structures of the heart based upon the received sound waves. [Echocardiography, 2004]

As the probe is fixed to the chest of the patient, it continuously emits ultrasound waves. The machine then can receive constant information about the heart structures as it changes during its contraction. This helps in visualization of the heart muscles, valves and blood vessels in motion. The flow of blood inside the heart and blood vessels can also be seen through color Doppler which is usually in two colors – blue and red. The blue color indicates the blood moving away from the transducer and the red indicates the blood which is flowing towards the transducer. Through this, it is possible to identify the abnormalities of blood flow into the heart such as leakage of blood through values.

Apart from this the pressure differences between one part of the heart and the other could also be found out as the ultrasound waves reflecting off from blood would change its sound wave length based upon the speed with which the blood flows which is commonly called as the blood velocity. This is known as the Doppler phenomenon. Blood moves at higher velocities when there is a greater pressure difference between two parts of the heart. This speed of the blood could be calculated by the Doppler equipment of the echocardiogram and an estimation of pressure gradient through the pulmonary valve could be quantified.

Similar concept works for Doppler radars which is very useful as a weather forecasting tool with the use of radio waves. These radars are used to calculate the frequency change in returning radio waves. Waves bounce back by something moving away from the antenna change to a lower frequency whereas waves from an object moving toward the antenna change to a higher frequency. A computer which is connected to a Doppler radar uses these frequency changes to show directions and speeds of the winds blowing around the rain drops, insects and other objects that reflected the radio waves and provides pictures. [Williams, 2002]