Lesson 3 Nature of Sound.pdf

NATURE OF SOUND  LESSON OBJECTIVES Describe the nature of sound and how it is propagated ; Compare the speed of sound in different media and at different temperatures Describe the Doppler effect; and Apply the principles of the Doppler effect in solving problems related to it. ...

NATURE OF SOUND  LESSON OBJECTIVES Describe the nature of sound and how it is propagated ; Compare the speed of sound in different media and at different temperatures Describe the Doppler effect; and Apply the principles of the Doppler effect in solving problems related to it.  How is sound produced? Sound is created when something vibrates, sending waves through the air or other materials. A vibrating object causes the surrounding molecules to also move. This disturbance travels Sound waves take time to reach the receiver. through the medium (solids, liquids, and gases) until it reaches our ears.  How is sound produced? Examples of Sound The vibrations of the guitar strings, The vibrations produced in the when plucked, create a sound. person’s vocal cords travel as sound waves. NATURE OF SOUND ELEMENTS OF SOUND: Source Medium Detector or receiver  SOUND PROPAGATION Sound waves cannot travel without a medium. For example, you cannot hear the loud sound produces from the powerful nuclear reactions in the Sun because there is nothing that will transport the sound waves. Sound waves travel in different types of medium, not just in air example in approaching vehicle, and when you are underwater. Sound cannot travel in a vacuum. Since sound is produced by a vibrating object, particles are needed for these vibrations to move from the source to the receiver. In determining the velocity for a longitudinal wave that is traveling through a solid rod, the following expression is used: 𝐸 V= 𝑝 Where E is a constant proportionality value called the elastic modulus that depends on the material and p is the density of the material To determine the speed of sound traveling through a liquid or a gas, use the following equation: 𝐵 V= 𝑝 Where B is the constant value called bulk modulus, which depends on the shape of the material, and p is the density of the material.  Density- gives the compactness of the particle as they occupy space in the structure of the substance. It is the ratio of the mass and the volume of the substance. The more compact the particles are, the higher the density is. Elasticity- the more elastic the material, the more it allows sound to travel quickly because particles can easily compress and expand. The ability to bounce back after being disturbed facilitates the faster transfer of energy Effect of Temperature on the Speed of Sound in Air If the medium of the sound waves is gas, temperature considerably affects the speed of the sound A higher temperature means higher KE, which means faster motion. Sound traveling in air at a temperature of 0°C has a speed of 331 m/s. When the temperature is increase to 20℃, its speed becomes 342 m/s.There is an increase in speed as temperature increases. In order to get the speed of sound in air at varying temperatures, the following equation is used: v=(331+0.60T)m/s where T is the temperature in degree Celsius and m/s is the finaI unit of v. Effect of Temperature on the Speed of Sound in Air Effect of Temperature on the Speed of Sound in Air Doppler Effect When there is variation in the perceived frequency of the sound due to the motion of the source with respect to the observer, a phenomenon called the Doppler effect occurs. It is named after the Austrian physicist Christian Doppler who studied this phenomenon in 1842. He observed that the pitch of the source is dependent on frequency (fs). Doppler Effect fs SUMMARY QUIZ #4 QUIZ #3 1. It is created when something vibrates, sending waves through the air or other materials. A. Sound B. Light C. Heat QUIZ #3 2. It gives the compactness of the particle as they occupy space in the structure of the substance. A. Pressure B. Density C. Thickness QUIZ #3 3. Which of the following is an element of a sound? A. Source B. Noise C. Barrier QUIZ #3 4. A phenomenon when there is variation in the perceived frequency of the sound due to the motion of the source with respect to the observer A. Tyndall effect B. Variation C. Doppler Effect QUIZ #3 5. Sound cannot travel in vacuum A. True B. False