Understanding of sound waves and Uses of ultrasonic waves.

Sound cannot travel through a vacuum.

Sounds travel at a greater speed in steel than in air.

The speed of sound will be highest in humid air with high temperatures.

Thunder is heard much after a flash of lightning is seen because light travels much faster than sound.

The walls and ceiling of an auditorium are covered with fibrous material, such as glass fibre, to absorb sound and prevent echoes.

Bats can fly in the dark because they are guided by ultrasonic waves produced by them.

A device used for measuring the depth of the sea is called a fathometer.

A diagnostic technique commonly known as ultrasound is based on recording echoes of extremely high-frequency waves.

The frequency of a sound wave is related to its pitch.

Understanding about loudness

The loudness of a sound depends on amplitude. The relative loudness of a sound is measured in decibels (dB). More than 85 dB can impair or damage hearing.

Quite - 20 db

Conversation - 65 db

Traffic sound – 70 db

Rock music – 120 db

Speed of sound

We call sound waves in air longitudinal waves. Sound waves can travel in air, gases, liquid and solid mediums but not in a vacuum. The speed of sound is measured in the unit; m/s. sound can travel about 330 m/s in air, about 1450 m/s in water and 5000 m/s in steel.

The speed of sound in air increases by 0.61 meters per second for each degree rise in temperature above 0⁰ C.

Understanding about echo

Do you know one thing? The word echo comes from Greek. Echo was the name of an angel who repeated every word.

When a sound wave is reflected by a distant obstacle, echoes are heard.

For an echo to be heard separated from the original sound, it must arrive 0.1 s after the original sound is made. This can happen if the minimum distance of the reflecting surface from the sound of sound is 17 m.

Supersonic speed

330 m/s is roughly 750 miles per hour. If the speed is greater than this, it is said to be supersonic speed.

Infrasonic sound and Ultrasonic sound

Sound waves with frequencies below 16 Hz are called infrasonic sounds.

Sound waves with frequencies above 20000 Hz are called ultrasonic sounds.

Uses of ultrasonic waves

Echoes of ultrasonic waves are used for measuring the depth of the sea bed or locating submerged objects. An apparatus called sonar is used for this purpose.

Ultrasonic is used for detecting flaws in the interiors of solids.

It is used for destroying microorganisms.

It is used for mapping structures for oil and mineral deposits.

Ultrasonics are applied widely in medical diagnosis and treatment. Here the different tissues send back echoes, which are picked up by sensitive microphones and turned into electrical signals on a television screen. From the pattern of the echoes, tumours, lesions and other abnormalities can be picked up within the liver, heart, kidney and other organs. Medical ultrasonography is ideal for use in human beings.