# Sound Waves (SOL 5.2)

Time:
Topic:
Concept:
SOL: 5.2

The student will investigate and understand how sound is transmitted and is used as a means of communication. Key concepts include

frequency, waves, wavelength, resonance, vibration;
the ability of different media (solids, liquids, gases) to transmit sound; and
communication tools (voice, Morse code, sonar, animal sounds, musical instruments).
Rationale:

## Goals:

Objective: The student will identify 3 out of 4 characteristics of sound when posed with written questions. (What does high frequency represent? Etc.) The student will be able to orally state a connection between our last unit, the ocean, and any sound characteristic. (Dolphins make an ultrasonic sound.) The child will distinguish between a high and a low pitch with 85% accuracy by interpreting that frequency and showing it on a chalk board.

Affective domain: The student will respect his or her classmates and remain quiet so that different sounds can be heard. Children will work cooperatively in pairs of two. Children will share chalkboards cooperatively.

Psychomotor: The student will try making different sounds and drawing his or her own sound frequency interpretations.

## Materials:

Karaoke machine with microphone
Laptop with frequency display
Christina Aguilera’s “What a Girl Wants”
Mya’s “Ghetto Supastar”
Guitar
Pick
Miniature chalkboards (10)
Chalk (11)

## Procedure:

Advanced organizer: Why hearing is mysterious. Read “The Hearing Process.” Read “What Sound Is.” Note that we don’t understand how we hear pitch. Science has not yet explained it. And we don’t know how we hear loudness, either.

Connect with a previous unit:
What sounds did we learn about when we studied the ocean? Remember the dolphins? Some dolphins communicate at frequencies that are too high for our human ears to hear. We only hear parts of the sounds that they make. This is because they communicate with ultrasonic sound.

Does anyone know one way that doctors use ultrasound? There are many ways that sound is used in the medical profession. Can you think of any?

(ultrasound fetus images)

Ultrasonic- relating to acoustic frequencies above the range audible to the human ear, or above approximately 20,000 hertz

Infrasonic- having frequencies below those of audible sound
Define these terms on the board.

Play previously recorded computer sound that shows a high sound moving to a low sound. Show children the frequency display. Ask them what they notice about the differences after everyone has seen the display.

Children should note that high pitch has frequency with crests close to crests and troughs close to troughs.

Introduce boards and chalk.

Pass out chalk and boards.

Pluck guitar string.

Tell the children that you will play two notes. One will be higher than the other. Wait until 2 sounds are plucked, then raise your hand when you know which one is higher. Show a high frequency wave on the board. Show a low frequency wave on the board. Play two sounds on the guitar, have the child draw what the first sound looks like compared to the second one. Model first on the board. At this time, identify crest and trough.

Ask: What must silence look like?

Ask: What would an ultrasonic sound look like? (very high frequency waves)

Ask: What would an infrasonic sound look like?

Repeat guitar plucks. Let children practice listening and translating the frequency wave onto their boards.

Play first 6 seconds of “What a Girl Wants.” Tell students to draw the frequency on their boards. Play first 6 seconds of “Ghetto Supastar.” Which one has a frequency with the shortest distance from crest to crest? What does this distance translate to? High Pitch– Ghetto Supastar.

Let students try making a sound and having their classmates interpret them on their boards.

Call 4 different students up and let them each make a sound into the microphone. Have the class write the interpretation of the sound (high or low frequency) onto their boards.

Have children identify all of the troughs, all of the crests, and count the wavelengths on the different wavelengths above.

## Closing:

Ask students to write on their boards what they learned about frequency today. Ask one or two students to explain aloud how to express frequency or amplitude. Dismiss class.