Unit 1 Sound Teacher Guide

Unit 1 Sound Teacher guide

Investigation 2: Making and Hearing Sound

Introduction

In this investigation, Students explore how sound is produced by vibrating things and causes things to vibrate. They make models of vocal cords and eardrums, and they build and test simple musical instruments.

Students will gain experience with both inquiry skills and content, including:

·  Asking a question about objects and events in the environment

·  Conducting a simple investigation based on systematic observation

·  Employing simple equipment and tools to gather data and extend the senses

·  Using data to construct a reasonable explanation

·  Presenting results to others

·  Understanding that sounds are caused by vibrating object that set up vibrations in the air

·  Understanding that sound makes our eardrums vibrate and send signals to the brain

·  Understanding that when we blow air across our vocal cords, they vibrate and make sound

·  Developing abilities of technological design

·  Proposing and implementing a solution

·  Evaluating the design

·  Understanding the process of measurement and units

·  Using representations to model and interpret physical, social, and mathematical phenomena.

·  Collecting data using observations, surveys, and experiments

·  Using the language of mathematics to express mathematical ideas precisely.

·  Recognizing and applying mathematics in contexts outside of mathematics.

Discussion Guide

Sounds come from things that vibrate. A vibration is something moving back and forth in a regular way. Things that vibrate within our range of hearing (30 to 15,000 vibrations per second) make sounds that we can hear. All musical instruments have some part of them that vibrates and makes the musical sound.

Students cannot observe their vocal cords and eardrums directly, but they can build a comprehensible model of each. They can observe that the tightening of rubber bands raises the pitch, as it does with vocal cords. They can observe that a balloon vibrates in response to sounds, and can make something connected to it (a paper clip) move, as does the eardrum.

The building of musical instruments should cement the idea that every instrument must have a source of vibration, which students should identify in each case. There are several ways of creating the vibration – scraping a string (violin), hitting a string (piano), blowing across an opening (flute), blowing past a reed (saxophone), blowing to make the lips vibrate (trumpet), and hitting solid things, like drumheads, cymbals, or bells. The more energy is put into the vibration, the louder the sound.

Additional Teacher Background

Sounds travel through the air and water as pressure changes, and through solids as vibrations. Understanding the mechanism (pressure changes in air and water, and vibrations in solids) is more appropriate for older ages. At this level, students should be aware that sound travels through air, liquids, and solids, carrying vibrations from one place to another. They can observe vibrations from their vocal cords making a balloon drumhead vibrate in turn, and ask how the sound got there (through the air). They can put their ear against a tabletop and tap the table, and notice that the sound is louder traveling through the table than when it travels through the air.

All instruments that make a specific pitch have something that vibrates at a specific frequency. Strings that are tighter or shorter make higher pitches. Examples are violins, guitars, banjos, and pianos. In wind instruments, it’s the length of the air column that determines the pitch. Shorter pipes are higher. Examples are flutes, saxophones, trumpets, trombones, xylophones, and bagpipes.

The most basic instrument – the human voice – is also very complex, and it can make an enormous range of noises and sounds. Vocal cords are made to vibrate by air passing across them, rather like the whistle you can make by holding a piece of grass between your thumbs. Muscles control the tightness, and hence the pitch, of the sound. The quality of the sound is controlled by the shape of the mouth, tongue, and lips.

There is a further feature of all instruments: something must amplify the vibration and send it into the air, so that it can be heard and sound pleasant. Students at this level needn’t know how resonance works, but they should identify what is resonating – a soundbox (guitar), the air in a tube (trumpet), or a solid piece of wood or metal (cymbal).

Here are some websites with pictures and sounds of classical instruments.

http://www.thirteen.org/publicarts/orchestra/ (play a sound a match it to the picture)

http://www.mathcs.duq.edu/~iben/home.htm (information about instruments of the orchestra, with playable sound examples)

http://www.sfskids.org/templates/instorchframe.asp?pageid=3 (Try “Instruments of the Orchestra” and “The Music Lab”)

http://library.thinkquest.org/5116/(has pictures, but the writing is advanced)

When students build their instruments, be sure they can identify the source of vibrations, what determines the pitch (if there is one), and how the sound is amplified.

The kinds of instruments your students build will depend in large part on the materials they have available. Look through the following list and see what you (or they) can obtain.

PICTURES, OR REFERENCE: HOMEMADE MUSICAL INSTRUMENTS

Sources: Rubber-band banjos and a java jive bass, Alex Sabbeth, John Wiley & Sons, 1997

Science workshop – sound, noise & music, Mike Seller, Shooting Star Press, 1995

My first music book, Helen Drew, Dorling Kindersley, 1993

Instrument

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Materials

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Notes (see pictures below)

String bass / Long pole or meter stick, string (fishing line), resonator box / See picture
Rubber-band banjo / Piece of wood, plastic container with top, rubber bands, cardboard / Rubber bands around the neck, notches cut in container, cardboard bridge. See picture
Box harp / Open box, rubber bands, carboard bridge / Rubber bands of different tightness or weight across an opening. See picture
Box harp 2 / Open box, rubber bands, cardboard bridge, pencil / Rubber bands of different length across an opening. See picture
Fishing-line guitar / Wood board, screws, eyelet screws, fishing line / Fishing line on wood base, tighten with eyelet screw. Knots with fishing line are hard. See picture
Hose horn / Garden hose, funnel / Make trumpet-like sounds with lips. See picture
Bottle organ / Soda bottles / Fill various amounts, blow across tops
Bottle xylophone / Glass bottles or glasses / Fill various amounts, hit with wood stick. See picture
Double reed oboe / Rolled-up paper tube, straw (cut end), tape / Challenging to play. See picture
Shakers / Bottles filled with small things like beans / No pitch
Triangle / Bolts, string / Bolts suspended by string to make a clear sound. See picture
Chimes and bells / Things that make a nice sound when hit, string / Hang them up, see how they sound
Drums / Anything you can hit / Don’t make a single pitch

String bass stringbass [add labels]

Banjo banjo

Box harp boxharp

Box harp 2 boxharp-alt

Fishing line guitar fishingline guitar

Hose horn hose horn

Bottle Xylophone bottle xylophone

Oboe oboe

Triangle triangle

It will be challenging to build instruments that give long, pure tones, which are the easiest to study with the Sound Grapher. If some students have access to “real” instruments, bringing them in and studying their sounds and how they are built would be a valuable addition to the unit.

Suggested Timeline

The amount of time you spend on introductory discussions, data collection, and analysis, will determine your overall timeline. The following represents a possible timeline.

* One half class period - "Setting Up" discussion

* One class period - Trial I: Rubber Bands and Vocal Cords

* Two class periods - Trial II: Build a Musical Instrument

* One class period - Analysis and "Wrap Up" discussion