The transmission of sound:
(1) voice spread by media, gas, liquid and solid can transmit sound. Vacuum can not sound;
(2) the sound is propagated in the medium in the form of sound wave. The propagation speed of sound in the medium is related to the medium. The speed of sound propagation in solid is fastest, second in liquid and third in gas. (cork is an exception, cork cell wall is thin, and internal bubbles are many).
(3) the velocity of sound is also related to temperature. The velocity of sound is about 340m/s in the air of 15 degrees C, and the higher the temperature is, the faster the propagation of sound.
(4) the reflection of acoustic waves occurs at the interface between two media, forming an echo. If the human ear wants to distinguish the original and the echo, the echo to the human ear is more than 0.1s later than the original. If 0.1s is not enough, the echo and the original sound can only make the original sound stronger.
(5) using echo can measure distance, such as how deep the sea is, and how far it is from the obstacles.
Loudspeaker is a kind of switching device that transforms electrical signals into acoustic signals, and the performance of loudspeakers has a great influence on the quality of sound. The loudspeaker is one of the weakest devices in the sound equipment, and it is one of the most important parts for the sound effect. There are many kinds of loudspeakers, and the price varies greatly. Audio power can make the paper basin or diaphragm vibrate and resonate with the surrounding air through electromagnetic, piezoelectric, or electrostatic effects, and make sound.