See the outdoor sound lesson for more sound activities (some loud and some need the space of outdoors).
Indoors, choose a selection of the following activities.
Introduce the concept of sound with students making their own sound sandwich or laughing cup.
Help students figure out how the sound is made.
Sound sandwich: the vibration of the elastic band is transmitted to molecules in the air, causing them to vibrate. This vibration of molecules travels through the air to our eardrum. In our ear the vibration is converted to a nerve signal that is sent to our brain, so we sense the vibration as a sound.
Use slinky to model how sound vibrations travel: Sound Vibration Model.
Explore sound travelling through different materials with the sound through solids activity.
While students are experimenting, visit them to show them how sound travels through bones.
Go outside to demonstrate sound echos, how echolocation works.
Show on a ukelele or other musical instrument how pitch can be changed by changing the length of a string/tube. Discuss other instruments that students play and how the pitch changes in them.
Sing a class song using the instrument, students accompanying on their sound sandwich/laughing cup.
Explore the pitch of sound through sound with a ruler.
Note that the constant noise of this class builds the energy level of the students quite dramatically. Including the 'Sound through string' activity keeps things a bit less hectic as students' ears are blocked. Outside lesson also a good option.
Ruler vibrations too subtle/complex for younger grades - skip for an hour workshop with the other activities.
Stuff to try: http://science-notebook.com/sound01.html