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The Nature of Sound

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2 The Nature of Sound

3 Important Vocabulary Compressional Wave Pitch Intensity Loudness

4 What Sounds Did You Hear This Morning?

5 What Causes Sound? Sounds are produced by vibrations of objects Voice is produced by the vibrations of your _________ The speed of sound waves depends on the temperature and elasticity of the matter in the medium Atoms are __________ in a solid. As a result sound is transmitted faster in solids than in air. Compressional Waves: matter vibrates in the same direction as the wave travels

6 Compressional Waves When you squeeze the coil together, the crowded area is called a compression This compressed area expands, spreading the coils apart and creating a less dense area The less dense area of the wave is the rarefaction Have same characteristics as transverse (wavelength, amplitude, frequencies and velocities)

7 Wavelength: the distance between two compressions or two rarefactions of the same wave Frequency: number of compressions that pass a place each second Amplitude: depends of the energy content of the wave

8 Comparing Media: Solid, Liquid, Gases The speed of sound depends on The medium it passes through And the temperature of the medium Air the most common medium Sound waves can be transmitted through any type of matter Liquids and solids are better conductors of sound than air because the particles have a greater influence on each other.

9 Think about it… If you were on the moon, would you be able to hear someone else talking?

10 Speed of Sound As temperature of a substance increases, the molecules move faster and therefore collide more frequently, making sound travel faster Think about fireworks. Have you seen one explode before you actually hear the explosion? What does this tell you about the speed of light and the speed of sound?

11 Determining How Far Away Is a Thunder Storm? Count the time interval between when you see a lightning bolt and when you hear thunder. You see the lightning bolt before you hear the thunder because…

12 The Ear Being able to make sense of sound waves when having a conversation involves three stages 1.Gathering and amplification of the compressional waves by the ear mechanisms 2.Conversion of these waves into nerve pulses 3.Decoding these signals to the brain

13 Frequency and Pitch Pitch: highness or lowness of a sound Depends on the frequency of the sound waves The higher the frequency, the higher the pitch Lower the frequency, lower the pitch Noise has no definite pitch

14 Intensity and Loudness The intensity of a sound wave depends on the amount of energy in each wave Intensity of a sound wave increases as its amplitude increase Loudness is the human perception of sound intensity.

15 Doppler Effect Doppler Effect: is the change in frequency of a wave (or other periodic event) for an observer moving relative to its source.

16 Frequency of Sound Waves p. 513

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