Sound and Sound Waves (Background Information)

Next Generation of Science Standards

4th Grade Waves

Sound and Sound Waves (Background Information)

Sound is a type of energy made by vibrations. When an object vibrates, it causes tiny air

particles to move. Imagine you are sitting in a quiet room with a friend. If you clap your

hands, the shock causes the air around your hands to begin vibrating. When air particles

vibrate, they bump into other particles near them. Then these particles begin to vibrate and

bump into even more air particles. When the air particles begin vibrating the air inside

your ear, you hear a sound. This chain reaction continues until the particles run out of

energy. This is what we call a “sound wave.”

So what happens when you turn the volume up on your stereo or television? Well, you’re

not only turning up the volume, you’re actually turning up the amplitude! Volume is the

intensity of a sound wave. It is directly related to amplitude, which is the height of a sound

wave. Imagine a drawing of ocean waves. The highest part of the wave is the crest. The dips

in-between each wave are called “troughs.” The distance from the highest part of the crest

to the lowest part of the trough is amplitude.

Sound waves and ocean waves may be made of different things, but they work the same

way. Changing the amplitude of a sound wave changes its loudness or intensity. If you are

playing a guitar, the vibrations of the strings force nearby air molecules to compress and

expand. The volume of your guitar playing depends on how hard or softly you pluck the

strings. When you pluck a string gently, the sound will be softer because you have

transferred less energy to the string. By using less energy, the string does not vibrate as

much and will move less air than if you had plucked the same string forcefully. On the other

hand, if you pluck the same string with a lot of force, the note will be much louder. When

you use more force to pluck the string, you are using more energy. This extra energy causes

the string to vibrate more, which helps it move more air particles for a longer time. A string

plucked with force has greater amplitude, and greater amplitude makes the sound louder

when it reaches your ear. Volume depends on amplitude. Greater amplitude produces

louder sounds.

http://wonderopolis.org/wonder/what-makes-sounds-louder/

Sound and Sound Waves (Background Information)

Amplitude - of a wave refers to the maximum amount of displacement of a particle

on the medium from its rest position. In a sense, the amplitude is the distance from

rest to crest or rest to trough.

Sound wave - is a traveling disturbance that travels through space and matter

transferring energy from one place to another.

Volume – the magnitude or intensity of a certain sound.

Crest -point on the medium that exhibits the maximum amount of positive or

upward displacement from the rest position.

Trough- point on the medium that exhibits the maximum amount of negative or

downward displacement from the rest position.

Wavelength- Distance between corresponding points of two consecutive wave, it is

measured from crest to crest or from trough to trough.

volume

Sound and Sound Waves (Background Information)

Acoustic/Sound Mirrors

A rare relic found in southeast England during the 1st World War. It is a 4.5 meter high

concrete structure that could pick up the reflected engine sound of aircraft approaching

from the sea. It has a trumpet-shaped “collector head” with a microphone that had wired

passed down a pipe to a listener seated in a trench nearby. The listener had a stethoscope

headset and would try to determine the distance and bearing of any enemy airships. Some

were able to detect aircraft up to 25 miles away.

Sound and Sound Waves (Background Information)

Common Core Extension:

Design and draw to scale an Acoustic Mirror using Google SketchUp.

Create an audio recording explaining an Acoustic Mirror.

Design and draw to scale your iPhone dock using Google SketchUp.

Create a PowerPoint presentation showing the design process with photos you have

taken during the building of your iPhone dock.

iPhone Sound Dock

Gail Dickinson Germantown Middle School gdickinson@madison-schools.com

Challenge:

Design an iPhone dock out of everyday inexpensive materials that supports an

iPhone & increases the volume in one direction without distorting the sound.

Questions to Consider:

What material reflects sound best, and is also inexpensive?

(ex. hard or soft, smooth or rough, dense or less dense)

What shape can direct the sound emitted from a speaker towards the listener and away

from others?

Where will the phone dock?

Where will the cord exit?

Can you use the phone without removing it from the dock?

How will the phone be supported?

Research:

History – Acoustic Mirrors aka Sound Mirrors

Acoustic materials (inexpensive)

Surface and composition of materials that affect sound waves

Shapes that redirect and enhance the volume of sound

Design:

Sketch out the design for your dock; include materials that will be used.

Create:

Build the prototype

Try it Out:

Test the prototype for iPhone support, redirection of sound and increased volume.

Make it Better:

Modify the prototype