Modified: 2020-03-18
Let's look at some examples of the interaction of media and sound. You may have inhaled helium and then spoken. When you did that, your voice sounded squeaky and high pitched. Why? Your voice changed because you were pushing helium instead of air through your vocal apparatus. Because of helium's physical properties your voice changed. Another example is how sound travels through sea water. Sea water conducts sound about 17 times faster than air does. So, sounds can be heard for long distances under the ocean. Submarines try to be silent as possible for that reason. The movie, "The Hunt for Red October," featured a sonar operator as one of its main characters. In that movie the Soviets had developed a new, quieter underwater propulsion system. The sonar operator detected it as a new and different sound. In real life, the Toshiba company of Japan sold some machining equipment to the former Soviet Union a few years ago. The U.S. government was upset because that machinery could be used to manufacture quieter submarine propellers.
Finally, do you remember the first time you heard yourself on tape? You probably said, "That's not my voice." But it was. You are the only one that hears your voice both from vibrations in the air and from vibrations in the bones of your head. Everyone else only hears the vibrations of your voice in the air. That is why singers recording a record use earphones. They want to hear how they sound to everyone else, not how they sound to themselves.