Physiscs unit 11

Physiscs unit 11

1. 11.1

   • All sounds come from sources which vibrate. They can make the sound of their instrument louder ar softer, they can control its loudness. They ca make the note higher or lower, they can change its pitch
     • 11.2
       • The Amplitude tells you the maximum distance the vibriting object moves from its rest position before it started vibrating. The number of vibrations per second is called the frequency of vibration. The symbbol for frequency is called Hertz.
         • 11.3
           • Air is made up of tiny particles called molecules. These molecules push on the next ones, and so on. The molecules only vibrate from side to side, but the vibration travels outwards through the air. We call this a sound wave
             • 11.4
               • If you connect a microphone to an oscilloscope, it will allow you to see a picture of the sound wave, as a line on the screen. the line is called a trace. When there is no sound (silence), the trace is a flat line. The air molecules are not vibrating. With a quiet sound, the trace goes up and down a bit in the shape of a wave. It has a small amplitude. With a loud sound, the trace goes up and down much more. Its amplitude is greater. high pitched sound= waves closer and higher low pitheed sound= the waves are more spread out
                 • 11.5
                   • The vibrations travel down the ear canal. The vibriting air pushes on the eardrum. The eardrum pushes the three small bones. The smallest bone vibrates against the Cochlea, which is a curled-up tube filled with liwuid. The vibrations travel through the liquid, stimulating the nerve cells inside the cochlea. These send electrical signals along the nerve to the brain. Sounds above 200000 Hz are beyond the range of human hearing. such sounds are known as ultrasound