Building a Stringed Instrument

<p>In this step, you will learn about sound waves and some of their properties.</p>

<p>As you learned in the last step, sound is a wave. But how does a wave travel through the air?</p>

<p>In the video, you saw that sound moves through the air because it affects the air molecules. Because of that, we call sound a <strong>mechanical </strong>wave. This is different than <strong>electromagnetic </strong>waves like radio or microwaves because they don&#39;t move through particles. That is why electromagnetic waves can move through space while sound waves do not.</p>

<p>Waves of all kinds have some key&nbsp;characteristics. These are Wavelength,&nbsp;<strong>frequency</strong>, <strong>amplitude</strong>,&nbsp;and <strong>speed</strong>.</p>

<p>In reverse order, <strong>speed </strong>is how fast the wave moves. For electromagnetic waves, this is about 300,000,000 meters per second. Sound waves&nbsp;move at a measly 343 meters per second. That is why when you see lightning strike, the light (an electromagnetic wave) is seen and then the thunder (sound wave) is heard several seconds later.&nbsp;<img alt="https://www.pcmag.com/encyclopedia/term/amplitude" src="/api/storage/uploads/legacy-images/iq1mgcyir5yuq7ecfgdcx9ntybe3/amplitude-wavelen.fit_lim.size_640x.gif" style="margin-left: 5px; margin-right: 5px; float: right; width: 369px; height: 262px;" /></p>

<p><strong>Amplitude </strong>is the height of your wave. Amplitude in sound waves relates to the volume or loudness of your sound. The greater the amplitude, the louder the sound is.&nbsp;</p>

<p><strong>Frequency </strong>is the number of waves (or oscillations since something vibrating is also oscillating) in a given amount of time. For sound waves, we use one-second intervals. The number of waves per second is measured in a unit called the <strong>Hertz </strong>(hz). When we tune our stringed instruments later, we will change the tension of the strings to change how the string vibrates and how many times it vibrates in a second!</p>

<p><strong>Wavelength </strong>is the physical distance the wave travels when it completes one cycle (you can measure it from peak to peak, trough to trough). You can calculate the wavelength by taking the speed of sound in meters per second (343m/s) and dividing it by the frequency (in cycles per second). For A4 (which we will find later is 440 hz), 343/440 is 0.78. This means that the wavelength for an A4 note is 0.78 meters long!</p>

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<p>Below is a brief video demonstrating the motion of sound waves in the air. Open up a <a href="https://phet.colorado.edu/sims/html/waves-intro/latest/waves-intro_en.html">copy of the simulation</a> and follow along with the video. There are a couple of questions after the video.</p>

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border-radius: 8px; will-change: transform;"><iframe allow="fullscreen" allowfullscreen="allowfullscreen" loading="lazy" src="https://www.canva.com/design/DAGB8sKaidk/Of1-Wa5PtcTByCsEwcayUg/watch?embed" style="position: absolute; width: 100%; height: 100%; top: 0; left: 0; border: none; padding: 0;margin: 0;"></iframe></div>

<p><a href="https://www.canva.com/design/DAGB8sKaidk/Of1-Wa5PtcTByCsEwcayUg/watch?utm_content=DAGB8sKaidk&amp;utm_campaign=designshare&amp;utm_medium=embeds&amp;utm_source=link" rel="noopener" target="_blank">SC: Stringed Instruments - PHET Waves</a> by Jim Stith</p>

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<p>How did amplitude affect the sound waves?</p>

<p>How did frequency affect the sound waves?</p>