Unit V: Sound
Introduction
General Instructional Objectives (and corresponding Specific Learning Outcomes) | Unit Content |
Knows terms
Understands the meaning of terms |
transverse and longitudinal waves, sine curve, amplitude, wavelength, frequency, hertz, period, wave speed, interference pattern, shock wave, infrasonic, ultrasonic, compression, rarefaction, reverberation, refraction, forced vibration, standing wave, bow wave, speed of sound, resonance, beats, pitch, loudness, modulation, partial tone, harmonic |
Understands scientific concepts | wave motion and speed, interference pattern, sonic boom, Doppler Effect, natural frequency, carrier wave, amplitude and frequency modulation (AM and FM), fundamental frequency |
Knows all laboratory procedures
Prepares a plan for an experiment Participates in classroom activities Respects the scientific process Displays a scientific attitude Demonstrates skills in laboratory work |
All content |
Instructional Foci
Now to dissect what we hear, sound. The teacher should begin by exploring where sound comes from. The answer is usually sound comes from vibrations of material objects. He/she should talk about the medium through which sound travels, the type of waves most commonly produced, the speed of sound, and the frequency of waves. Sound can also be reflected, which we call an echo or, in terms of multiple reflections, reverberation. An ultrasound, which most students should have at least heard of, is due to the reflection and refraction of high-frequency sound. The small relatively small amount of energy needed to produce sound should be discussed. Combining forced vibrations that match an objects natural frequency causes a dramatic increase in amplitude known as resonance. An example of resonance sometimes occurs when swinging on a swing. If somebody gives a small push to the swinger in rhythm with the frequency of the swinging motion, the amplitude is greatly increased. On the contrary, when the crest of a wave meets the trough of a wave their amplitude decreased to almost zero. This is called interference. Interference can be demonstrated by striking two tuning forks out of rhythm in a large room. If students walk around or sway their heads back and forth they will hear soft areas and loud areas produced from compressions and rarefactions adding and subtracting. If the two tones are of slightly different frequencies they will vary periodically in loudness. This is known as beats. Overlapping two combs of different teeth spacing will illustrate this phenomenon.
Finally, the last section of this unit will explore musical
sounds. Pitch, loudness, and quality should be defined and discussed. You
are then ready to study musical instruments and musical scales. Once these
topics have been introduced students should be asked to create their own
musical instrument, be it a blade of grass or a rubber band guitar. Students
should bring their homemade musical instruments as well as any real musical
instruments to class to be viewed in terms of frequency on an oscilloscope.
A brief study of how compact discs work would be an interesting way to
conclude the unit on sound.