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H I G H S A N DL O W S

W hen we talk about a sound,we might say it is high. Asmall bird’s chirp is a high

sound. Other sounds are described aslow, or deep. When we talk about howhigh or low a sound is, we are talkingabout its pitch.

The pitch of a sound is related to thefrequency, or speed, of the vibrationscoming from a sound source. High-frequency vibrations move quickly. Low-frequency vibrations move slowly. High-frequency vibrations produce a soundwith a high pitch. A sound with a low pitchcomes from low-frequency vibrations.

Adjusting a sound source such as amusical instrument to produce a certainpitch is called tuning.

HIGH FREQUENCY = HIGH PITCHLOW FREQUENCY = LOW PITCH

GETTING IN TUNEMost musical instruments make

sounds in one of three ways. Stringinstruments such as the guitar or violinmake sounds with vibrating strings.Musicians either pluck the strings ormove a bow across them. The strings aretightened or loosened with tuning pegs.Each string is tuned to a certain pitch.

INVESTIGATION2

11

Take Note

Each musical note has a specificfrequency. For instance, middle C is 262 vibrations per second. Itdoesn’t matter what instrumentplays the note. The frequency ofmiddle C is always 262 vibrationsper second.

Note Frequency (going up the scale) (number of vibrations

per second)

Middle C 262 doD 294 reE 330 miF 349 faG 392 solA 440 laB 494 tiHigh C 524 do

The note at the top of the scalehas exactly twice the frequency ofthe note at the bottom. Twonotes, one of which has twice thefrequency of the other, are said tobe separated by an octave.

542-2012 Physics of Sound_TEXT.qxd 12/7/07 3:42 PM Page 11

Other pitches can be produced bypressing down on the strings withthe fingers. This shortens the strings,making higher pitches.

In wind instruments such as theflute or trombone, sound is pro-duced by a vibrating column of air.Pitch is controlled by varying thelength of this column of air.

A flute’s pitch is controlled byplacing the fingers over the holes init. This shortens or lengthens thecolumn of air that vibrates insidethe flute.

INVESTIGATION2

Winds around the WorldWe’re used to seeing and hearingmany wind instruments. Tubas,saxophones, flutes, and clarinets arewell known. But there are other windinstruments you may not know about.

Wind instruments all over the worldvary in shape and sound. They all use avibrating column of air to make sound.People throughout the world have triedusing different materials to makemusic. They use what they find in theirown lands. That is why many of theseinstruments work the same way butlook different. However, someinstruments from different parts of theworld look a lot alike, too. Did youknow that bagpipes are played inEurope, Asia, and Africa? People havealways traded and moved from onecountry to another. Sometimes thisspreads musical instruments todifferent parts of the world.

The sheng is a Chinese windinstrument. It has many pipes and issimilar to a harmonica.

The zurna is a wind instrument ofTurkey. It is similar to an oboe.

The Middle Eastern nay and the Swaziumtshingo are both types of flutes.

Australian Aborigines play thedigeridoo. This instrument is a type of trumpet.

Panpipes, shown at right, are played inLatin America, Asia, and the PacificIslands. The pipes are different lengthsand are tied together. Each pipe is asimple flute.

Violin Guitar

Cello

12

542-2012 Physics of Sound_TEXT.qxd 12/7/07 3:42 PM Page 12

A trombone player’s lips vibrate against the mouthpiecewhen the player blows. The player tenses and relaxes the lipsto produce different pitches. The player also controls the pitchby moving a slide back and forth. This changes the length ofthe column of air inside the trombone.

With percussion instruments such as the kettledrum,sound is made by striking the surface. Pitch

depends on the tension (tightness or looseness)of the surface. The kettledrum can be tuned

to various pitches. This is done byloosening or tightening thesurface of the drumhead.

BIG SOUNDS, SMA LL SOUNDS

Tuning varies the pitch of soundan instrument makes. But the size ofthe instrument is important also. Big instru-ments generally make lower vibrationsthan small ones. The smaller theinstrument, the faster the vibrations andthe higher the sound.

Inside a flute, there is a smallercolumn of air than inside a trombone.

A cello has a bigger body and longerstrings than a violin. It also makes adeeper sound.

Bongo drums make higher sounds thanbass drums.

INVESTIGATION2

Trombone Flute Panpipes Bongos Kettledrum

13

542-2012 Physics of Sound_TEXT.qxd 12/7/07 3:43 PM Page 13

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