SCIENCE PRESENTATION

Sound

• Range of hearingUltrasound Infrasound

• Applications of UltrasoundUltrasonics

• Diagrams

•Topics covered

•Ultrasound is an oscillating sound pressure wave with a frequency greater than the upper limit of the human hearing range. •Ultrasound is thus not separated from 'normal' (audible) sound based on differences in physical properties, only the fact that humans cannot hear it. •Although this limit varies from person to person, it is approximately 20 kilohertz (20,000 hertz) in healthy, young adults.• Ultrasound devices operate with frequencies from 20 kHz up to several gigahertz.

Range Of HearingUltrasound

• Ultrasonics is the application of ultrasound. Ultrasound can be used for medical imaging, detection, measurement and cleaning. • At higher power levels, ultrasonics is useful for changing the chemical properties of substances• The potential for ultrasonic imaging of objects, was recognized by Sokolov in 1939 but techniques of the time produced relatively low-contrast images with poor sensitivity.• The power density is generally less than 1 watt per square centimetre, to avoid heating and cavitation effects in the object under examination.

•ULTRASONICS

• The potential for ultrasonic imaging of objects, was recognized by Sokolov in 1939 but techniques of the time produced relatively low-contrast images with poor sensitivity.• The power density is generally less than 1 watt per square centimetre, to avoid heating and cavitation effects in the object under examination.• High power applications of ultrasound often use frequencies between 20 kHz and a few hundred kHz. Intensities can be very high; above 10 watts per square centimeter, cavitation can be inducted in liquid media, and some applications use up to 1000 watts per square centimeter.• Such high intensities can induce chemical changes or produce significant effects by direct mechanical action, and can inactivate harmful bacterias.

•Sonar (originally an acronym for SOund Navigation And Ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, communicate with or detect objects on or under the surface of the water, such as other vessels. •Two types of technology share the name "sonar": passive sonar is essentially listening for the sound made by vessels; active sonar is emitting pulses of sounds and listening for echoes. •Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of "targets" in the water.

SONAR

• Sonar may also be used in air for robot navigation.The term sonar is also used for the equipment used to generate and receive the sound. •The acoustic frequencies used in sonar systems vary from very low (infrasonic) to extremely high (ultrasonic).• The study of underwater sound is known as underwater acoustics or hydroacoustics.

• The detection, classification and localisation performance of a sonar depends on the environment and the receiving equipment, as well as the transmitting equipment in an active sonar or the target radiated noise in a passive sonar.• The sound reflection characteristics of the target of an active sonar, such as a submarine, are known as its target strength.• A complication is that echoes are also obtained from other objects in the sea such as whales, wakes, schools of fish and rocks.• Passive sonar detects the target's radiated noise characteristics. The radiated spectrum comprises a continuous spectrum of noise with peaks at certain frequencies which can be used for classification.

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PERFORMANCE FACTORS

•Ultrasound Scanner

•SONAR

Uses Of Ultrasonic Waves