Introduction
The purpose of this article is to continue expanding the knowledge or learning about the essential phenomenon of sound, and as we know it travels or propagates from one space-time to another and this is done through a certain material or elastic medium such as air (gas), liquid or solid, in general, the sound to reach our auditory systems uses the air.
So far we have been able to notice that sound waves when propagating from an emitting source to a receiver get in their way with any kind of obstacles and these make these rays or sound waves undergo changes generating intrinsic phenomena such as reflection, absorption, transmission, diffraction and now refraction.
When we introduce ourselves to the refraction of sound we could say that this phenomenon constitutes a change of direction of these waves when passing or crossing a certain material medium or obstacle, this characteristic is also found in another essential phenomenon such as light, then my dear readers, just like light, sound when passing through different material media its speed will be affected bringing as a consequence a change of directionality of the sound waves.
It is very important to highlight that sound can also be refracted by a single material medium, but at different conditions of temperature, density, elasticity, pressure, among other conditions related to the non-homogeneous material medium through which the sound will propagate.
Sound refraction
This type of phenomenon allows us to highlight the change of direction of certain sound waves when they pass from one place to another, and this aspect is due to the fact that the speed of these sound waves changes due to the non-homogeneity of the obstacles or material media crossed by the sound.
The refraction of sound as we have expressed can occur in the same material or elastic medium, for example, air, and this happens when the properties of the medium are not equal, for example, we could easily express that the air temperature when it is sunny is not the same as at night, therefore, the layers of air that is close to the earth's crust are at higher temperature than those layers above these, then, the speed of sound waves increase with increasing temperature.
In relation to the above we can say that this increase in the speed of sound is because its molecules oscillate faster, therefore, as the sound is caused by a vibration this makes the sound is transmitted with greater speed, taking into account that this analysis is in relation to the air, therefore, when there is sun the lower layers or closer to the earth's crust allow sound waves to travel faster because of its high temperature.
In relation to the nights we can say that the opposite happens, that is, that the sound travels at lower speed and this is because the layers of air closer to the earth manage to cool faster than those layers that are above these, then, the sound rays emitted from the surface will curve downward and in the hot layers upward, and of course, this in relation to the temperature magnitude, as you can see in Figure 1 below.
Figure 1. Refraction of sound in air at different temperature conditions
In the previous figure 1, you could notice the phenomenon of refraction of sound waves in the same medium such as air in non-homogeneous conditions.
When relating to sound waves and refraction in the same medium we could point out another example, therefore, when two people are located at each end of a river or aquifer and try to communicate, surely in the early hours of the morning or at night such communication will be more effective because the air above the water will be colder and thus denser, surely in the early hours of the morning or at night such communication will be more effective because of the low temperature the layer of air above the water will be colder and thus denser, these conditions cause the sound to refract downward, however, the opposite happens when the sun heats up and the temperature rises as you can see in the following figure 2.
Figure 2. Refraction of sound rays in the same material medium
My dear readers, it is important to point out that the phenomenon of refraction has a greater effect when sound waves pass from a certain material medium to a different material medium.
Conclusion
In every moment of our lives there are a great number of phenomena that we cannot see or capture with our human senses, however, sometimes it is possible to do so, as in the case of sound, as long as these waves are within the audible range for our ears.
In this opportunity we relate to another intrinsic phenomenon in the propagation of sound such as refraction, and it represents in general terms the change in the speed of certain sound waves when passing from one material medium to another, however, it is also possible to observe it within the same material medium in non-homogeneous conditions as shown in Figures 1 and 2 above.
Until another installment, my dear Hive.blog readers.
Note: All images are my own and were created using Power Point and the animated gif was created with the PhotoScape application.
Recommended Bibliographic References
[2]Specular and diffuse sound reflection. Author: @rbalzan79.
[3]Sound absorption. Author: @rbalzan79.