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<br />.k <br /> <br />produced. This example demonstrates the relationship between a linear motion, the weight <br />bouncing on the spring, and its corresponding wave fonn. The Amplitude of the moving weight <br />is denoted as A on the diagram and corresponds with the maximum displacement of the weight <br />from its "at rest" position, or the peak of the wave fonn in the positive or negative direction. The <br />Period of the vibration is the amount of time taken to produce one complete cycle. The number <br />of cycles per second defines the Frequency of the periodic motion which is denoted by the unit of <br />Hertz, abbreviated as "Hz". <br /> <br />Comparison of Periodic Motion to Sound Waves <br /> <br /> <br />Expansion <br /> <br />Expansion <br /> <br />Air <br /> <br />Com ssion <br /> <br />Comp ssion <br /> <br />I <br /> <br />Ex an ion <br /> <br />Ex an ion <br /> <br />Loudspeaker <br /> <br />Figure 1.2 <br /> <br />The graphical representation of sounds in Figure 1.2 are Pure Tones, which are sounds made up <br />of a single frequency. A familiar example of a pure tone is the sound produced when a single <br />key of a piano is pressed. For instance, the middle C key on a piano vibrates the associated wire <br />at a rate of approximately 260 times per second or 260 Hertz. The vibration of the wire transfers <br />its motion to the sound board of the piano, which then vibrates at t.he same frequency, causing the <br />air adjacent to the sound board to fonn compression and expansion waves in the air emitting <br />outward from the sound board. When received by the human ear, this is regarded as sound. <br /> <br />4 <br />