1. SoundSection 3 What do you think? A violin, a trumpet, and a clarinet all play the same note, a concert A. However, they all sound different. What is the same about the sound? Are the frequencies produced the same? Are the wave patterns the same? Why do the instruments sound different?

2. SoundSection 3 Standing Waves on a String There is a node at each end because the string is fixed at the ends. The diagram shows three possible standing wave patterns. Standing waves are produced by interference as waves travel in opposite directions after plucking or bowing the string. The lowest frequency (one loop) is called the fundamental frequency (f 1 ).

3. SoundSection 3 Standing Waves on a String To the left is a snapshot of a single loop standing wave on a string of length, L. What is the wavelength for this wave? –Answer: = 2L What is the frequency? –Answer:

4. SoundSection 3

5. SoundSection 3 Harmonics n is the number of loops or harmonic number. v is the speed of the wave on the string. –Depends on tension and density of the string L is the length of the vibrating portion of the string. How could you change the frequency (pitch) of a string?

6. SoundSection 3 Click below to watch the Visual Concept. Visual Concept Fundamental Frequency

7. SoundSection 3 Standing Waves in an Air Column Wind instruments also use standing waves. –Flutes, trumpets, pipe organs, trombones, etc. Some instruments have pipes open at both ends while others have one end closed. –Air is free to move at open ends so antinodes occur. –Closed ends are nodes. The velocity of the wave is now the velocity of sound in air (346 m/s at 25°C).

8. SoundSection 3 Both Ends Open

9. SoundSection 3 Closed at One End