Introduction and Background
How popular is music among kids today? Examine the annual sales of pop CD's and cassettes, the figures are staggering. Add to this the sales of concert tickets and the amount of time kids spend watching MTV and the answer is quite clear, music is very important to kids today. Music is a significant part of American culture for young people. Headphones have become as much a part of everyday wear as sneakers. Kids just don't like to be far from their music.
Technology teachers can capitalize on this phenomenon through thematic activities that explore the relationships between music and sound. Mathematical, scientific and technological connections can be made through discovery activities that allow students to explore their own experiences while enjoying performances and sounds of their favorite groups.
This Thematic Design Unit (TDU) contains Discovery Activities that allow students to explore the nature of sound and its relationship to music. The Discovery Activities can be used in several different ways. Teachers can choose activities that are appropriate to their classroom situations. Selected activities can be set up in a modular fashion so students can rotate through each activity. Another possibility is to divide the students into teams. After completing the activity, teams can share or debrief what they have learned with the entire class. The information and data collected through Discovery Activities will later be used in more complex Design /Build /Apply Activities.
The Design /Build /Apply Activity is an essential part of the TDU. This activity will take an extended period of time and will allow the students to be creative while solving open ended design and build problems, using formal problem solving techniques.
Goals
Use formalized design and problem solving processes
Introduce portfolio record keeping methods as a means of documentation
Experience scientific inquiry
Apply the basic elements of material and structure studies
Apply the basic elements of acoustical design
Apply math, science, technology and other interdisciplinary connections
Apply physical modeling skills
Design/ Build/ Apply Problem Statement
The store next to the library is being renovated into a "Teens Only" center by a community group. The plan behind the "Teens Only" center is to provide a place where teenagers can go to listen to music, hang out and just have some fun. A major concern for the library board is the level of noise generated from the center and its impact on the atmosphere within the library.
You are an architect specializing in acoustic design who has volunteered to design and build a model for the proposed renovation. Your task is to research acoustical materials and their applications and use the data in your model. You will then make a presentation to the library board demonstrating how your design addresses the issue of keeping noise levels at an acceptable level.
Criteria
The store is 40' long and 40' wide with a 14' ceiling. The model must be built at a 1/2" = 1' scale.
The model must include two exits and a stage where the sound will be generated. The stage is 10' deep and 15' long.
The acoustic design within the model must reduce the decibel level of a sound source placed into the model by twenty-five percent may have to be adjusted by the instructor) when measured outside the model.
Testing Procedure
1. The sound source can be an alarm clock, radio, CD player, etc.. Adjust the volume to approximately 100 decibels when a sound level meter is placed three inches from the source.
2. When the model is complete, place the sound source in the model on the stage. Place the roof on the model. Using the sound level meter, check the decibel levels around the outside of the model. Calculate the reduction in sound level from the original levels.
Materials
Equipment
Technology, Science and Math Connections
Science
Math
Discovery Activities
1. Portfolio Preparation
Activity Goal: To share and discuss with the students the role of portfolios in the design process. To show and discuss exemplar portfolios.
Procedure: Students will use the portfolio to record their thoughts,
data and actions throughout the TDU. For example, prior to doing
the Sound Reflection Discovery Activity students should record
what they anticipate will occur. They will then record what actually
occurred during the activity and draw some application conclusions
from the experience.
2. Sound Absorption and Reflection
Activity Goal: To discover if sound will bounce off a hard surface as well as a soft surface? Can sounded be reflected?
A. Hold the sheet of cardboard upright on a table.
B. Place the two tubes on the table at angles to each other and the sheet of cardboard. Be sure the cardboard is close to but not touching the tubes.
C. Place the ticking clock into the outside end of one of the tubes.
D. Place your ear directly against the outside end of the second tube. Describe what you hear, take note of the volume, pitch and crispness of the sound.
E. Place your hand or a book over the inside end of the tube containing the clock. Repeat step "D".
F. Repeat step "D" covering the upright cardboard with various fabrics, foams and combinations of materials. Record your observations.
G. Try changing the angle between the tubes. Repeat step "D" and record your observations.
H. What conclusions have you made based on the results of this
activity?
3. How Does Sound Travel Through Materials?
Activity Goal: Does sound travel better through air (gas) or solids? Does sound travel through different materials in the same way?
A. Suspend the 24" aluminum rod with the two pieces of string tied near the ends of the rod.
B. Hold one string in each hand. Have a classmate rap the rod with a block of wood.
C. Record in your portfolio your interpretation of the sound. Pay attention to loudness, tone, and pitch. Remember, the sound is now traveling through the air.
D. Rap one string around each index finger. Put your fingers in your ears. Strike the rod again.
E. Record your impressions of the sound as compared to the previous experiment. F. Repeat the experiment by tying the various samples of materials to the string and placing the samples against your ear.
G. Record your comparisons and observations about the ability of the material you tested to conduct sound.
H. Based on this activity, what conclusions can you make about the ability of materials
to conduct sound energy?
4. What Does a Sound Wave Look Like?
Activity Goal : What does a sound wave look like? Do all sound
waves look alike, regardless of their level or pitch?
A. Using wax from a lighted candle, attach the head of a straight pin to the end of one prong on a tuning fork.
B. Clamp the tuning fork to the ring stand as show in the diagram.
C. Place a sheet of carbon paper under the pin. Carefully adjust the height of the pin so it lightly touches the surface of the carbon paper.
D. Strike the opposite prong on the tuning fork with a block of wood.
E. Slowly and steadily pull the carbon paper under the pin. Practice this process a few times until you get a good print of the tuning fork's wave pattern.
F. Repeat the process with different tuning forks.
G. Record you observations. Identity the basic wave characteristics.
H. What conclusions can you draw from this activity?
5. What Do the Sound Waves of Music Look Like?
Activity Goal: Does the music from different instruments have
their own special sound wave pattern? Are bass wave patterns the
same or different than treble wave patterns? The goal of this
activity is to investigate the sound waves produced by musical
recordings and to study the nature of their wave patterns.
A. Position the device you are using to play the recorded music so that it's speakers are horizontal to the table it is sitting on.
B. Place a paper plate on top of the speaker.
C. Place a single layer of rice grains on the plate forming a circle pattern. A diameter of five inches is sufficient.
D. Turn on the music and observe the motion of the rice. Record the direction and rate of movement of the rice.
E. Repeat steps C and D, this time increasing the bass and then repeat the process increasing the treble controls on the device. Record the motion of the grains of rice.
F. Based on your observations, what conclusions can you make about the wave patterns of different instruments?
Use authentic assessment methods for evaluations. These methods include portfolios, student presentations, scoring guides, teacher observations, oral exams and team self evaluation. Traditional assessment techniques can be used when appropriate.
The student portfolio is used to document student work. It provides the student a place to record their thoughts, ideas, impressions, data, decisions and reflections. The portfolio serves as a map tracing the path the student took in the development of their design solution. Each day the class works on the TDU an entry should be made into the portfolio.
Many teachers develop generic style portfolios that can be used for any design problem. Some portfolios can be specifically tailored to a particular activity; Headings that are commonly found in portfolios include: Statement of the Problem, Specifications and Constraints, Societal and Environmental Considerations, Possible Design Solutions, Final Solution, Resources of Technology, Self Evaluation and Daily Log Sheet. Students fill in all these sections as they progress through the design process.
The portfolio becomes a valuable tool when assessing the student's work. On occasions, the prototype or model submitted by a student does not work or is of poor quality. A review of the student's portfolio may demonstrate some terrific ideas and concepts for a design solution that the student was just unable to carry out. The process is just as important as the final product.
(See the sample portfolio provided)
Sound is a form of energy that causes molecules to vibrate. Sound travels in waves, compressing and expanding the space between molecules in a material, causing them to vibrate. Materials can be used to reflect or absorb sound waves based on their ability to conduct sound.
In this Discovery Activity, students will have an opportunity to find out which materials will reflect and which materials will absorb sound waves. The results of their experimentation will be used in the selection of acoustical building materials for their model.
Sound from the ticking clock will travel down the tube as it causes the molecules of air in the tube to vibrate. Hard, smooth surfaces tend to reflect sound energy while soft, sculpted surfaces tend to absorb sound energy. Reflection of sound occurs when sound waves bounce back from materials that will not absorb the wave energy. Students will find that hard materials will reflect the sound better than soft materials. For this reason, concert halls usually use heavy curtains to prevent sound waves from bouncing off walls causing echoes.
The incoming wave or wave striking the surface of a material is
called the incident wave. The wave that bounces back is called
the reflected wave. The law of reflection states that the angle
of incidence equals the angle of reflection. Acoustical engineers
use this principle in the design of reflective panels throughout
an auditorium to control the reflection of sound energy. The angle
of reflective panels will determine where the sound will go after
it bounces off the panel.
The students can experiment with the angle of incidence and reflection by changing the angle between the tubes and recording the changes in volume and pitch of the ticking clock.
Sound waves move differently through different materials. Elastic materials transmit sound better than non-elastic materials. The term "elastic" in this case, means the ability of the molecules in a material to return back to their original position after a sound has waved moves through it. Solids are more elastic than liquids and gases because the molecules do not move far and quickly return back to their original position. Molecules in solid materials are also packed tighter together so vibration easily can be moved from one molecule to another.
Sound travels faster through elastic materials. Sound moves at different rates through different materials. The speed of sound in air is about 340 meters per second. Sound moves through steel at a rate of about 5200 meters per second as compared to 60 meters per second through rubber because steel is a more acoustically elastic material. The speed of sound moving through materials is also effected by the material's density. Sound moves through dense materials much slower because of the mass of the molecules. For example, the speed of sound through lead is much slower than through aluminum.
The amount of energy in a sound wave is called "intensity". Intensity determines the loudness of a sound. The greater the intensity, the louder the sound. Sound intensity is measured in units called decibels.
The pitch of a sound is a measure of how high or low the sound is. High or low does not refer to the loudness of a sound. High or low refers to the frequency of the sound. Frequency is how fast the molecules in a material vibrate. Sound waves of high frequency are heard as high pitch sounds.
In Discovery Activity #3, students will have an opportunity to test various materials and investigate their ability to conduct sound waves. The information gathered from this exercise will be used later in the selection of acoustical building materials for their models.
A wave is a disturbance caused by the transfer of energy through a medium such as a solid, liquid or gaseous material. When you toss a pebble into a pond, the surface of the pond is disturbed as waves travel along the surface of the pond. The waves transfer the kinetic energy that is produced by the pebble.
Materials transfer sound energy by vibrating parcels or molecules within the material. The energy is transferred from one particle to another as the particles vibrate in a circular motion.
High pitch sounds are created when particles in a material vibrate very quickly. If we were to graph of the waves produced by high pitch sounds we would see a great many waves created per unit of time. We would see the frequency of that high pitch sound. Hertz (Hz) is the unit of measure we use to describe the frequency of a wave.
Discover Activity #4 will allow the students to see the different shape and patterns of waves created by differently pitched tuning forks.
Music is composed of many sounds. The sounds vary in pitch, loudness and timbre. Musical instruments for create the variety of sounds we enjoy. All musical instruments work by vibration.
Blowing into a saxophone makes a small wooden reed vibrate. The reed makes a column of air in the instrument vibrate. The keys on the instrument change the length of the air columns, thus creating different sounds. A short length of air produces high pitch sounds, while a longer air column produces low pitch sounds. Trumpet players make their lips vibrate, which in turn makes air in the trumpet vibrate. Drum heads vibrate when struck with a drum stick and guitar strings vibrate when plucked with a finger or pick.
When the vibration of one thing makes something else vibrate, it is called resonance. String instruments use a sound box to make them louder. The vibrating string makes the air inside the sound box vibrate by resonance.
When listening to music, we can often pick out the different instruments being played. This is because each instrument has its own unique timbre or sound quality. Timbre is created when something in the instrument is made to vibrate at a particular frequency. Actually, an instrument produces many frequencies at the same time. The blending of these pitches or frequencies gives the instrument its distinctive timbre.
Discovery Activity #5 will demonstrate to students the effectsof combining sounds. It will visually allow them to see the vibration patterns an frequencies produced by low pitch and high pitch sounds. Students will see that each instrument produces its own vibration pattern because each instrument has its own timbre.
Speed of a wave = frequency x wavelength
Speed of sound = frequency x wavelength
Design, Build and Apply Activity
Engineers who specialize in acoustics (the science of sound) design spaces that will produce the best sound. Acoustical engineers must consider the shape, size and materials used in construction. Poorly designed spaces may contain echoes or even dead spots where sounds may not be heard. Reflection panels and acoustical materials are commonly found in auditoriums, theaters, amphitheaters, and concert halls. When strategically placed, they help the audience hear the sound produced by the musicians or actors.
The goal of this activity is to have students discover basic information about sound and acoustics and apply this information in a problem solving situation. A student's typical design might include panels reflecting sound and acoustical materials absorbing sound for the purpose of keeping the decibel levels outside the room at an acceptable level.
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