Major players in the drama of 19th-century Texas were definitely the Comanches who at this time swept down from the cool highlands of the southern Rockies, and, mounted on horses, drove other tribes from West Texas.
What is SOUND? The periodic mechanical vibrations and waves in gases, liquids and solid elastic media. Specifically the sensation felt when the eardrum is acted upon by air vibrations within a limited frequency range, ie 20 Hz to 20 kHz. Sound of a frequency below 20 Hz is called infra. STRUCTURE-BORNE SOUND.
Sound is a form of energy, just like electricity and light. Sound is made when air molecules vibrate and move in a pattern called waves, or sound waves. Think of when you clap your hands, or when you slam the car door shut.That action produces soundwaves, which travel to your ears and then to your brain, which says, âI recognize that sound.â.hen we draw a sound wave, the wave peaks and valleys are close together or far apart. Sound waves vibrate at different rates or âfrequenciesâ as they move through the air. Frequency is measured in cycles per second, or Hertz, after the German physicist who experimented with sound in the 19th century.