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 mechanical wave. This means that some motion causes sound to be produced. It is usually a vibrating membrane, which creates alternate high and low pressure points in the medium. These pressurised pockets of medium then vibrate (note that they do not move forward.