encouraging students to lead the inquiry
It’s important to let the children make all the observations and generate the entire list without help from you. In fact, if their list of observed lip-movers is missing a sound, your activity will actually be the richer for it. In the following example, two digressions, one for rhyme and one for whispering will help you get to your goal.
an interesting digression: rhyme
Imagine that your students’ list of lip-movers includes /v/ but not /f/, but that you get both /p/ and /b/. Find a rhyming pair, like pail/bale. Determine how many sounds (not letters!) there are in each word. There are 3 in each, and the last two are the same. This is a good chance to talk about rhyme. In this case, these are exact rhymes, because the last two sounds in the syllable are exactly alike. And the words rhyme, not because of their spelling--which is different--but because of their sounds. See the sidebar.
But the first two sounds of each word are different in an interesting way. Where, according to the children’s observations, is the /p/ sound produced? And where is the /b/ sound produced? In exactly the same place, as it turns out (top lip touches bottom lip, air builds up behind the closed lips and the n is released all at once, etc.).
In fact, the only difference is that one sound, the /b/ sound, includes the vibration of the vocal folds, while the /p/ sound does not. Have the children put their fingertips on their throats and feel the difference. Have them make each sound repeatedly until they can feel it. Then ask them to make the /p/ sound a few times and then add vibration.
Now they can go back and try out this new theory on /v/. Ask them to take away the vibration from /v/ and see what they get. What they get is the /f/ sound!
They will see much more of this vibration/no vibration distinction in the future.
another digression: whispering
Your students are now very close to a functional definition of whispering. Whispering is a little more complicated than just “talking softly.” In fact it depends more on the eliminating vibration than on lowering volume. To test this theory, ask if anyone knows what a stage whisper is. If not, have them try whispering softly and then louder and louder. At what point does the whisper turn into something else?
If the children are too young to have encountered the term ‘stage whisper,’ have them put their fingers on their throats again and ask them to recite a sentence normally and then in a whisper. Have them try a soft whisper and a loud whisper. Have them recite normally in a soft voice and then a loud voice. What do they think causes the difference in sound?