Science_Lab_Yellow / Lesson 5: Sound Recorded
Sound Recorded What will we be learning today? How Is Sound Recorded? A microphone includes a diaphragm, a coil of fine wire, and a magnet. When you sing, speak, or play music into the microphone, sound waves make the diaphragm vibrate. The pitch of the sound determines how fast the diaphragm vibrates. The loudness of the sound determines how far the diaphragm moves with each vibration. Blank tapes are coated with scrambled magnetic particles. During recording, the electric current from the amplifier arranges the particles on the tape into a pattern-a "code" for the sounds. When you push "play," the process reverses. The magnetic particles on the tape create a current in the coil. This current vibrates a stiff paper cone in the speaker. This creates the sound waves you hear. Compact discs do not store sound in magnetic patterns. Instead, a computer in CD-recording equipment translates the sound waves into a code. The code is a combination of 1s and 0s. Then a laser beam uses the code to cut millions of tiny pits into a blank compact disc. About 85,000 pits cover only one inch of the disc. When you play a CD, a laser beam shines on it. The flat parts of the CD reflect light back to a small computer. The computer changes the pattern of these reflections back into sound. Next time you strum a guitar, pound a drum, or sing a tune, keep in mind what you have learned. The different musical sounds you make on an instrument or when you sing are different pitches. You can play an instrument at different volumes-to make the sounds louder or softer. You sing louder when you take a deeper breath and breathe out harder. You use loudness and pitch to express different emotions, too. Let's Review What We Learned Today!