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SOUND 24.2

SOUND 24.2. Chapter Twenty-Four: Sound. 24.1 Properties of Sound 24.2 Sound Waves 24.3 Sound Perception and Music. Chapter 24.2 Learning Goals. Justify the classification of sound as a wave. Analyze sound interactions at boundaries.

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SOUND 24.2

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  1. SOUND 24.2

  2. Chapter Twenty-Four: Sound • 24.1 Properties of Sound • 24.2 Sound Waves • 24.3 Sound Perception and Music

  3. Chapter 24.2 Learning Goals • Justify the classification of sound as a wave. • Analyze sound interactions at boundaries. • Explain how factors like temperature and pressure affect the behavior of sound waves.

  4. Key Question: How can resonance be controled to make the sounds we want? Investigation 24B Resonance in Other Systems

  5. 24.2 What is a sound wave? • Sound waves are pressure waveswith alternating high and low pressure regions. • When they are pushed by the vibrations, it creates a layer of higher pressure which results in a traveling vibration of pressure.

  6. 24.2 What is a sound wave? • At the same temperature and volume, higher pressure contains more molecules than lower pressure.

  7. 24.2 The wavelength of sound • The wavelength of sound in air is similar to the size of everyday objects.

  8. 24.2 The wavelength of sound • Wavelength is also important to sound. • Musical instruments use the wavelength of a sound to create different frequencies.

  9. 24.2 Standing waves • A wave that is confined in a space is called a standing wave. • A string with a standing wave is a kind of oscillator.

  10. 24.2 Standing waves • The lowest natural frequency is called the fundamental. • A vibrating string also has other natural frequencies called harmonics.

  11. 24.2 Standing waves • The place on a harmonic with the greatest amplitude is the antinode. • The place where the string does not move (least amplitude) is called a node.

  12. 24.2 Standing waves • It is easy to measure the wavelength of a standing wave on a string. • Two harmonics equals one wave!

  13. 24.2 Standing waves in pipes • A panpipe makes music as sound resonates in tubes of different lengths. • The natural frequency of a pipe is proportional to its length.

  14. 24.2 Standing waves in pipes • Because frequency and wavelength are inversely related, longer pipes have lower natural frequencies because they resonate at longer wavelengths. • A pipe that must vibrate at a frequency 2 times higher than another pipe must be 1/2 as long. If the long pipe has a frequency of 528 Hz, what is the frequency of the short pipe?

  15. 24.2 Standing waves in pipes • Blowing across the open end of a tube creates a standing wave inside the tube. • If we blow at just the right angle and we match the natural frequency of the material and the sound resonates (spreads).

  16. 24.2 Standing waves in pipes • The open end of a pipe is an open boundary to a standing wave and makes an antinode. • The pipe resonates to a certain frequency when its length is one-fourth the wavelength of that frequency.

  17. 24.2 Sound wave interactions • Like other waves, sound waves can be reflected by hard surfaces and refracted as they pass from one material to another. • Diffraction causes sound waves to spread out through small openings. • Carpet and soft materials can absorb sound waves.

  18. 24.2 Reverberation • The reflected sound and direct sound from the musicians together create a multiple echo called reverberation. • The right amount of reverberation makes the sound seem livelier and richer.

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