1.1 Sound and music activities  (Page 3/5)

Discussion questions

• Do thicker rubber band "strings" sound higher or lower than thinner ones? (Answer: thicker should sound lower.)
• Do tighter strings sound higher or lower than looser ones? (Tighter should sound higher.)
• Do shorter strings sound higher or lower than longer ones? (Shorter should sound higher.)
• Do there seem to be differences in how loud and soft or how dull or clear a string sounds? If so, what seems to cause those differences?
• What determines whether the sound of a string is loud or soft?
• What happens to the sound if they pluck with one finger while touching the string lightly with another finger? (No "twang"; the touch stops the vibrations.) If their instrument design allows it, what happens when they hold the string tightly down against the instrument and then pluck it? (The shorter vibrating length should give a higher pitch.)
• After their experiments, can they explain what happens when a player holds a string down with a finger? What if the same string is held down in a different spot?
• Based on their observations, do the students feel they could tell which strings of an instrument are the low strings just by looking at them closely? (For an extra activity, arrange for them to try this with a real instrument.)
• Can the students come up with possible reasons why the thickness, length, and tightness of a string affect its frequency/pitch in the way that they do? (For example, why does a shorter string have a higher frequency/pitch?) (It may help on length to remind them that the longer the waves are, the less frequent they will be.)

Wind instruments activity

Objectives and assessment

• Objectives - The student will explore the effects of air column size (and shape) on the frequency and amplitude of standing waves in the air column, using empty glass bottles, and water if necessary to vary air column size.
• Evaluation - Assess student learning using worksheets or answers to discussion questions.

Materials and preparation

• If you do not want your students working with glass jugs and water, plan to do this as a demonstration.
• You will need several narrow-necked bottles, all the same size and shape OR several narrow-necked bottles of varying sizes and shapes. Bottles should be empty and clean. Make sure before the class begins that your bottles give a clear, reasonably loud sound when you blow across the top of them. If necessary, practice getting a sound. Large glass jugs with an inner lip diameter of approximately one inch work well.
• If using bottles of the same size, you will also need water to fill them to varying depths. If you are using this approach, food coloring is very useful to clearly show the depth of the water.
• If plastic recorders are available to your students, or a player of a woodwind or brass instrument is available for a show-and-tell, they can be used for an extra demonstration.
• For older or more independent students, you may want to make copies of the discussion questions.

Procedure

1. If using same-size bottles and water, fill each bottle to a different depth (for example, an inch in one bottle, two inches in another, three inches in a third and so on). If you have food coloring, add a few drops to the water in each bottle so it is easy to see the depths.
2. Make the air in a bottle vibrate by blowing steadily across the top of the bottle.
3. "Play" each bottle in turn, and arrange them in order from the highest sound to the lowest.
4. If you have the time and inclination, you can even try to "tune" the bottles by adding or pouring out water.
5. If recorders or a wind instrument are available, demonstrate how covering and uncovering the holes on the instrument changes the pitch. Explain that the main vibration in the instrument is happening in the air inside the instrument (just like the air in the bottles), in between the mouthpiece and the first hole that the air can escape from..