Here are a few more peeks into the 3/4 grade study of sounds. I made a replica of the gold record that was launched with the Voyager space missions in the 1970's (Wikipedia Voyager Golden Records). The purpose of the gold record was to communicate using sound with any alien race that might discover our spacecraft. I didn't tell the students the story (and only a couple already knew what it was) and I presented it to them as something that had been found on an alien spacecraft that had collided with one of our earth satellites. I gave them the record without explanation, and encouraged them to try to determine what the object was about and how to decipher it. A number students were able to recognize the markings on the record as representations of sound waves, and all had logical ideas about what it could be and what to do with it. I then played them some of the sounds that were recorded on the actual gold records, and we talked about what sounds from earth would be important to include and what it might communicate to an alien race. The students also insightfully suggested that perhaps an alien race might not be able to experience sounds from Earth, even if they could decipher the record instructions, if the aliens did not have sound for one of their senses.
Speaking of the perception of sound by non-human beings, we also investigated the use of echolocation, both by bats and by blind humans. There are a few people who have learned to use sound just like a bat to navigate the world without sight (Blind Man Uses Echolocation). After learning about these unusual people, we tested our own abilities to determine sound direction without our eyes by being blindfolded and having a partner make snapping sounds from different places in front, behind, and to the side of us. Most of us were fairly good at locating the direction a sound is coming from, although we couldn't really hear the echo of the sounds that are used by animals and humans that have true echolocation.