Question

what is propogation of sound ?

Answer 1

Sound is a phenomenon described as a wave traveling in media. It is better illustrated with an example.
When I talk, I am producing a sound wave which will propgate through the air. Here, air is the media. Theoretically, if I tried to talk in a zacuum you wouldn't hear anything because there is no "media" to propagate the sound in.
Basically what happens when I talk is that the speed and quality of the sound coming from my mouth (determined by how loud I am talking, the fundamentals and harmonics unique to my voice box, and how I articulate the air to form words and sounds in my mouth) will pressurize the air immediately surrounding my mouth in a specific way. This pressurization will be relieved by pressuring air next to it, and so on and so forth. This transfer of pressure is called a wave. Specifically, it is a longitudinal wave because the displacement of oscillation of my wave (to and from mouth direction) is the same direction as the propagation (sound goes away from me). When this pressure reaches your ears, it will apply that pressure to your eardrum and it will be transmitted to your brain after passing through a series of ear bones and along a nerve to be interpreted as a sound.
As sound travels, it may lose energy due to the environment.
For example, if I say something 10 feet away from you, you will hear it more softly than I will because of the amplitude decrease of the wave as it travels since it will lose energy whilst traveling in the air.
Similarly, we can purposely disrupt the waves by interrupting them with a machine, like when you speak into a fan. The fan blades chop parts of the sound wave which is why you hear a funny shaking sound within your voice if you talk into a fan.
I hope that helps!

Answer 2

Sound is a sequence of waves of pressure which propagates through compressible media such as air or water. (Sound can propagate through solids as well, but there are additional modes of propagation). During their propagation, waves can be reflected, refracted, or attentuated by the medium. The purpose of this experiment is to examine what effect the characteristics of the medium have on sound.

All media have three properties which affect the behavior of sound propagation:
1. A relationship between density and pressure. This relationship, affected by temperature, determines the speed of sound within the medium.
2. The motion of the medium itself, e.g., wind. Independent of the motion of sound through the medium, if the medium is moving, the sound is further transported.
3. The viscosity of the medium. This determines the rate at which sound is attenuated. For many media, such as air or water, attenuation due to viscosity is negligible.