CE Physics: Wave

1. Sound wave that we heard is of frequencies between 20 Hz to 20,000 Hz (the audible range). Our ears cannot sense individual compression and rarefraction of the sound wave. Instead, the ear senses the total effect of the vibrations of air particles. A wave with larger amplitudes, i.e. larger displacement of both crest and trough, results in larger intensity because the particles vibrate to a larger extent, which causes higher compression and rarefraction effects to our ears. Hence, a louder sound is heard.
2. Air particles need to vibrate. If not, sound wave would not be formed. The statement that ".... particle remains louder all the time..." is physically meaningless. It is the result of vibration of air particles that produces the sound we heard. A single air particle cannot produce sound wave.
3. Interference, reflection, refraction and diffraction are properties of waves. In other words, a wave possesses all these properties.

1) still louder. It is because the louder or softer of a sound is depended on the amplitude of the wave, not only the crest.

2)sound is a wave which is transfered by the collide of molecules, when a molecule collides the other, it will leave the original position and cause a displacement. If the graph present in a straight line, that means the molecule doesn't move, no sound is presented.

3) If the thing only shows interference, we cannot call it WAVE,
but there maybe something just shows interference