Doppler Effect

The situation going on in this video is called the "Doppler Effect." The Doppler Effect is when a siren or sound changes from a high pitch to a low pitch. The pitch of a sound is determined by the frequency. This frequency will change when the source of the wave is moving. Between the time that one sound wave and the next one are emitted, the source of the sound moves forward. The wave speed stays the same but the distance between the waves is shortened. This means the waves are at a higher frequency. Therefore the pitch appears to sound higher as the source travels away from you. In the video below, one can see how the waiter's version of the song is quite different from the original song (heard in the car). As the car passes by quickly, the waiter hears the music. Instead of hearing the actual pitch, he hears the pitch rising as the car travels further away. Therefore, his concept of the pitch of the song is different from the actual pitch.

Science Question 1:

"If a tree falls in the forest, and there's no one there to hear it, does it still make a sound?"

The falling of the tree will not make a sound, if there is no-one there to hear it. The tree falling will create vibrations and therefore cause sound waves. Unless there is a brain/ear to process the vibrations the falling of the tree will not make a sound. An eardrum and a brain needs to be present. These vibrations must be interpreted by a living person/animal. If not, the falling tree will not make a sound.