That means sound would tend to focus and thus increase its apparent loudness.Ĭool air bends sound and thus increases amplitude This gradient of speeds would result in a lens effect due to refraction of sound. The temperature varies according to the distance from the surface of the water. Since the temperature of the water in a lake or ocean is usually cooler than the normal air temperature, the air just above the water level is cooled by the water. The direction of the sound waves change slightly. The same thing happens when sound enters a material in which its speed is slower than in normal air. (See Refraction of Light for more information on this subject.) The image is displaced, because the light rays were refracted. You have seen refraction when light passes through a pane of glass at an angle. When a wave strikes a material in which it travels slower, its direction is changed slightly if it strikes the material at an angle. Refraction of the sound waves in cooler air and the reflection off the surface of the water effect the sound that is heard. Speed of sound decreases closer to cooler water Effect of refraction and reflection
![water and soundwaves water and soundwaves](https://nashvillefunforfamilies.com/wp-content/uploads/2018/11/Soundwaves-outdoor-slides-1024x683.jpg)
The follow chart is the air temperature and speed of sound at different heights above the water. The air temperature would then increase at further distances from the water until it reached the normal air temperature. If the water was at 15.5° C (60° F), the air just above the surface would be close to the same temperature. The relationship between the speed of sound and the air temperature is approximated from the equation:
![water and soundwaves water and soundwaves](https://i.ytimg.com/vi/y2Pzum5y7pw/maxresdefault.jpg)
When the air temperature is 24° C (75° F), the speed of sound is 346 meters per second (m/s) or 775 miles per hour (mph). With sound, the amplitude of the waves relates to the loudness of the sound that we perceive.Īmplitude of waves decreasing as they spread Speed and temperature
![water and soundwaves water and soundwaves](http://feaforall.com/wp-content/uploads/2019/01/water-drop.png)
You can see this with water waves in a pond. As any waveform expands or spreads out from its source, its amplitude decreases.