The methodology of propagation of sound waves

Sound propagation

1. Manit Shah Physics Presentation Grade 9 Sound

2. Effect of density: Since we know Speed of sound(V)= √ γ P/ ρ , thus we can see that V inversely proportional to 1/ √ γ . Effect of temperature: The increase in the temperature causes the increase in the speed of sound meaning it is directly proportional. The rate of the increase of V is 0.61 m/s for increase in 1 ° C. Factors Affecting Speed Of Sound In A Gas

3. Effect of humidity: Speed of sound in air is directly proportional to the humidity in air. The increase in moisture causes the density of air to drop thus increasing speed of sound in air. Effect of direction of wind: Speed of sound increases if it is being propagated in the direction of flow of wind. And it decreases if it is propagated in the opposite direction to the direction of flow of wind. Cont.

4. Effect of pressure: We know that V= √ γ P/ ρ , so if P is doubled then the volume will get halved so the density will also be doubled. Making the ratio of pressure:density remain same. Effect of amplitude: The speed of sound is not dependant on the amplitude of the wave. Effect of Wavelength: The speed of sound doesn’t depend on the wavelength. Factors not affecting the speed of Sound in air.

5. Sound Light Sound waves cannot travel in vacuum. Light can travel in a vacuum. Speed of sound is 330 m/s Speed of light is about 1 million times faster- 300,000,000 m/s. Speed of sound is max in solids, lesser in liquids and least in gases. Speed of light decreases as a medium gets optically denser. Longitudinal mechanical waves. Transverse electromagnetic waves.

6. Consequences in large difference of Speed of light and sound. Thunder: When thunder strikes the flash is seen a few seconds before the sound is heard. When a cricketer strikes the ball with his bat the sound is heard just seconds after it is seen. When the starter fires the gun , spectators see the gunshot few seconds before the sound is heard.

7. Set up 2 positions A and B at a high altitude and at a distance of about 1 km. When the person at A fires the gun the person at B has to time the time interval between the flash and sound on a stopwatch. The same will be timed by person at A when the person at B fires the gun. Let the times be t 1 and t 2. The average of these two times will be the time taken by sound to travel 1km. Experimental determination od Speed of sound in air.

8. Thus the average is –t=(t 1 +t 2 )/2 From this we can determine the speed of sound. V=d/t NOTE: This value will not be exact due to different factors like human error, humidity, and temperature. ,etc. Cont.

9. A human ear can hear sounds in the frequency range of 20Hz to 20kHz, also known as human audible range In reality this audible range varies from person to person. It can also be affected by age. The sounds below 20Hz are known as infrasonic sounds, while the sounds above 20kHz are known as ultrasonic sounds. Some animals can produce infrasonic as well as ultrasonic sounds. Infrasonic, Sonic and Ultrasonic

10. These are just some of the animals that can produce infrasonic or ultrasonic or both.

11. Ultrasound has a high energy capacity Ultrasound has a high directivity meaning it travels along a well defined straight path and doesn’t bend on contact with edges of objects. Properties of Ultrasound

12. Uses of Ultrasonic sound SONAR Ultrasonography-image of patients organs Echo Cardiography- image of patients heart Bats use it to detect objects in their path or predators approaching them Ultrasound is also used to drill holes and make minute cuts of desired shapes in materials like glass.

13. Ultrasonic sound is the sound of frequency higher than 20kHz. Supersonic is used for objects travelling at a speed higher than the speed of sound. Like jet planes,etc.\ Difference between Ultrasonic and supersonic.

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