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SOUNDSOUNDWhat is it?What is it?

There are two ingredients for sound. First, we need a VIBRATION, then a MEDIUM.

VIBRATIONVIBRATIONA vibration occurs when something “wiggles” back and forth really fast.

For example, a

or a

or your own

What is a MEDIUM?What is a MEDIUM?Sound involves a vibration plus a medium. A medium is just something that the vibration passes through to get to our ears. Usually, this is just air. The guitar string vibrates and runs into air molecules, which run into more air molecules, creating a wave of air molecules all the way to your ears. Sound can also travel through a solid and a liquid. Have you ever tapped on your desk (a solid) when your ear was on it or heard things underwater (a liquid)?

*What do you suppose a wave of air molecules is called?

*If you were to play a guitar on the moon, would you hear it?

Sound wave

No. There is no air on the moon, so there is no medium for the sound to travel through.

VOLUME/AMPLITUDEVOLUME/AMPLITUDE

Have your parents ever told you to turn down the volume on your stereo? We all know that volume, or amplitude, is a word we use to describe how loud or soft something is. But what makes a sound loud or soft?

VOLUME/AMPLITUDEVOLUME/AMPLITUDERemember that we said that sound involves a vibration plus a medium. Volume, or amplitude, tells us about the SIZE of that vibration. If I play a chord on the guitar LOUDLY, we can see the strings vibrating very widely.

Click on picture

VOLUME/AMPLITUDEVOLUME/AMPLITUDE

Now if I play the same chord softly, notice how the strings barely move back and forth at all. It is the exact same group of notes, but because the strings are not moving as much, the volume is reduced.

Click on picture

PITCH/FREQUENCYPITCH/FREQUENCYPitch, or frequency, is about how high or low a note is.

Can you think of some HIGH sounds?

How about some LOW sounds?

And all three together…

And in between low and high?

PITCH/FREQUENCYPITCH/FREQUENCYVolume or amplitude is about how LARGE or SMALL a vibration is. Pitch or frequency is about how FAST or SLOW a vibration is.

FAST vibrations produce HIGH sounds.

SLOW vibrations produce LOW sounds.

Do you think these piano strings are vibrating quickly or slowly?

How about these piano strings?

PITCH/FREQUENCYPITCH/FREQUENCY

How fast or slow something vibrates determines what note is being produced. Just like the speed of your car is measured in Miles Per Hour (MPH), the speed of a vibration is measured in Vibrations Per Second (VPS).

Listen to this violin play an “A”. How many times per second do you think this note is vibrating? In other words, how many times is the violin string moving back and forth every second? (click HERE)

10? 25? 50? 100?

Actually, this note is vibrating 440 times every second!

PITCH/FREQUENCYPITCH/FREQUENCYVibrations per second, or VPS, is a unit of measurement called a HERTZ (Hz). The pitch you just heard is called “Concert A” and is the note that orchestras tune to. It vibrates at 440 Hz, or 440 VPS.

We know that music and science are related, but did you know that music is also related to mathematics?

Are you ready to do some multiplication and division?

THE OCTAVETHE OCTAVERemember that concert A that vibrates at 440 Hz? Eight notes above that (one octave) we have another A. This one vibrates at 880 Hz. An octave below A 440 we have an A that vibrates at 220 Hz. If you think you see a pattern here, raise your hand! What is the pattern?

A 440

A 880

A 220

Click on the speaker icons to hear each note.

THE OCTAVETHE OCTAVEThe pattern is simply this: When we go up an octave, the Hz doubles. When we go down an octave, the Hz is halved. All three of the notes you heard are A’s. They all vibrate at different frequencies, but they are all multiples or dividends of A 440.

Let’s listen to all three A’s at the same time. Notice you can here three different pitches, but they are actually the SAME NOTE played in three different octaves. (click here)

What would be the frequency of an A that is TWO octaves lower than A 440?

110. Were you right?

What Changes a Pitch?What Changes a Pitch?So how does an instrument produce different notes? In other words, what is it that makes a string vibrate faster or slower? There are TWO ways to change the frequency of a vibrating object.

1. Shorten or lengthen the vibrating object.

Click on picture

What Changes a Pitch?What Changes a Pitch?

2. Make the vibrating object tighter or looser.

Click on picture

THE SCIENCE OF MUSICTHE SCIENCE OF MUSIC1. The bigger the vibration, the __________the sound.

2. The faster the vibration, the __________ the sound.

3. Sound consists of a __________ and a __________.

4. A pitch that vibrates twice as fast as another pitch is said to be one ___________ higher.

5. A __________ occurs when something moves back and forth really fast.

6. A _________ is something that a vibration passes through to get to our ears, such as air.

7. ___________ is my favorite subject.