Seeing Sound

Ayse Kalkan-SavoyNSF GK-12 Fellow

Vibes and Waves in ActionCenter for Advanced Computation

and TelecommunicationsUniversity of Massachusetts Lowell

What do we need to have sound?

• Sound source– Can be anything that vibrates.

• Medium– Sound needs a medium; solid, liquid, or gas

• Detector– Perception of the observer.

How does the sound source create sound?

• The vibrations from sound source creates vibrations of pressure.

• Vibrations of pressure moves in the medium in the form of a pressure wave.

• The number of vibrations per second stay the same during the travel of this wave.

• Our ears receive the pressure wave, and we perceive it as sound (limited to 20-20K vibrations/sec).

Oscilloscope

Oscilloscope (scope): A device to observe electrical signals

Visual Analyzer

• Click on Visual Analyzer icon.

1. Change the top drop-down list value to Stereo Mix or ..2. Y-axis: Make sure to deselect “Log”.3. X-axis: select x8

http://www.onlinetuningfork.com

Overview

• Sound is vibrations of pressure wave.• Properties:

– Wavelength– Frequency– Period– Speed

Overview

• Frequency: vibration (cycle) per unit time• Hertz : cycle/sec• Wavelength: length of wave for one cycle• Cycle time (Period): Time for one cycle of

the wave.• Higher frequency -> smaller wavelength

SEEING SOUND INSTRUCTIONS PART A

1. Double click on “Visual Analyser” (VA) icon on your desktop. 2. At the top, there is a data field with a “scroll down” button. It is set to

“Microphone”. Change it to Stereo Mix. 3. At the right bottom, there are panels for Y and X axes. In Y-axis panel, uncheck

“Log”. 4. In X-axis panel, in the first field with a “scroll down” button, select “x8”. 5. Click on “On” button at the top-left. 6. On your desktop, double click on “Internet Explorer” icon. 7. When it starts, at the URL address field, type http://www.onlinetuningfork.com 8. Click on the first tuning fork, and observe the scope (top) and spectrum (bottom)

windows of VA. What are they displaying? 9. Click on the other tuning forks. Observe the signals on scope and spectrum

windows. Compare the waves for each tuning fork? What is the relation between the wavelength and frequency?

PART B

1. Plug in the microphone to the hard-drive (pink socket on the hard drive). 2. On VA, change the input type setting back to “Microphone”. 3. Hum. Observe the signal, and find its frequency.

Science Lesson Plan Teacher:

*This template is available in electronic form. 1

Period: Class: Date(s): SETTING THE STAGE Essential Question

Can we see sound?

Content Objective(s) (Student-friendly)

- Observe pure sound signal. - Define frequency - Find the relation between frequency, and wavelength.

Connection to previous or future lessons

In the previous lesson, we talked about color vision, and each color being different wavelength of light. This lesson will continue with observing sound waves. We will investigate more on the meaning of wavelength, and frequency and how the sound differs as these parameters are changed. After an introduction to Matlab lesson, there will be a Matlab sound lesson. This lesson will focus on sound as a function of time. The students will create sound using sin function in Matlab.

Critical Thinking Questions

Period is the time for one cycle of sound. What is the relation between period and frequency?

Key Vocabulary wavelength, frequency, pitch

Materials Needed/Safety

N/A

ACTIVE INSTRUCTION

• Launch (Engage)

To get attention of students, and to give direction on the answer for “What is sound?”, the class will start with ringing a metal bell, or gong.

• Investigation (Explore)

1. The lesson will start with the discussion of what sound is. We will do this by answering: - What do we need to generate and support transmission of sound? - How does the sound source create the sound? - How does sound travel? A slinky will be used to show the travel of sound waves. We will review definition for longitudinal and transverse waves. We will spend a short time discussing that wave movement is displacement of energy rather than that of the particles of the medium. 2. We can see the movement of sound wave at a fixed position in space, using

Science Lesson Plan Teacher:

*This template is available in electronic form. 2

oscilloscopes. A picture of an oscilloscope will be shown, and introduce the software defined oscilloscope as our device to see the sound waves. The software we will use is “Visual Analyzer”. 3. The students will be asked to start the software. To save time, we will use a configured application from a folder on the network. The sound input will be set to ‘stereo mix’ to input sound directly to the application. 4. We will open the web-site: http://www.onlinetuningfork.com. 5. There are three tuning forks on this site. Their frequencies are displayed below their images. Clicking on one creates the tuning fork vibration sound. We will click on the first one, observe the wave in time domain, and see what the spectrum shows. We will compare the period, frequency, and type of sound from each tuning fork. 6. We will define what frequency is. 7. We will analyze what we mean with low and high pitch. If time allows: 8. One computer with the right settings will be used to see the signal from an actual tuning fork (standard 440Hz –note A) and show that it is very much the same. 9. The students will be grouped to share one microphone per group. They will be asked to hum, and observe the sound waves, and the frequency of sound. We will discuss the observations, such as whose is the highest pitch.

TIME FOR REFLECTION

• Summarization (Explain & Extend)

Review:

- Sound is vibration. - It travels as longitudinal waves. - Pure sound, that is when vibration moves as only one wave, is a sine wave. - Frequency is one important property of sound. It is the number of cycles

per unit time. When the unit type is seconds, frequency unit is Hertz. - Low frequency is considered low pitch. Low frequency sound has larger

wavelength than the higher one, and that is why the number of cycles is less.

- Longer sound travel medium of same shape allows longer wavelengths, and create low pitch sounds. Examples: tenor saxophone vs. baritone, cello

Science Lesson Plan Teacher:

*This template is available in electronic form. 3

vs. violin.

• Assessment (Evaluate)

- Can sound travel in outer space? - Compare cello and violin. Which one has lower frequency range of sound?

Can you make connection between the string lengths and their properties of sound?

- Can sound speed change with the air temperature?

• Homework