Fundamentals of waves in sound 3/10

Fundamentals of Waves

Many things travel in waves: light, sound, water, radio signals. How do waves work? How do they carry all of these things around the universe so quickly? When you think about it, light comes from your lightbulb as soon as you turn it on. As soon as the fire alarm starts, you can hear it. How can the voices of the singers at the opera be so high, while the trombone in the orchestra is so low?

There are two types of waves: mechanical and electromagnetic. Mechanical waves need medium (matter) to travel through, like a solid, liquid or gas. Sound is a mechanical wave. Electromagnetic waves can travel through vacuum (empty space) and don’t need medium to travel. Light is an electromagnetic wave.

When the frequency increases, the pitch does, too. So when you hear a singer holding out an extremely high note, both the pitch and frequency of their sound waves are high as well. Sound is produced when an object vibrates, so when you talk, your vocal cords vibrate to make the sound of your voice.

Sound can travel faster through denser objects.

• It goes 346 m/s in warm air
• It goes 500 m/s in aluminum
• And it goes 3,240 m/s in gold

In solids, sound can travel faster because the molecules are close to each other. In liquids, some energy is wasted in getting to the closest molecule. In gases, sound travels the slowest because the molecules are speeding all around and are spaced far apart from each other. In vacuum, or no space, there are no molecules to vibrate at all, and sound can’t travel.

S&EP: SP3 Conducting investigations

While experimenting to see what sound can travel through, we did a few labs to help us. We first hit our pencil against the table while we were sitting up, and then we hit it again when we pressed our ear to the table, which helped us determine that the sound it made could travel through solids. Next, we put it in a tub of water and saw that we could still hear it, even though it was in the water. Ad if we held it up in the air and did it, we could still hear it. This experiment helped us see that sound can travel through solids (the table), liquids (the water) and gases (the air around us).

XCC: Cause and Effect

Sound is created by a vibration. When you talk, your vocal cords vibrate and make the sound of your voice. This is a cause and effect relationship. Your vocal cords vibrate, causing your voice to talk as an effect. It can happen with any sound - the sound of a tuning fork being hit, the sound of your air conditioner turning on and off, the sound of your car wheels on the highway. Whatever the sound is, it began with the vibration of something and ended with being a sound.