Using high-speed cameras and a photography trick called Schlieren Flow Visualization (SFV), New Mexico mechanical engineering professor Michael Hargather recently created one video which depicts what invisible sound waves look like. The video shows for the first time what common and uncommon features and actions of sounds look like.
The SFV it works by using a tilted parabolic mirror to deflect it light. A projection of the image used to compare the deflected light against the original image, along with the non-deflected light, and the shadows obtained in this way are collected, processed and then interpreted.
This technique has been used in the past for images of heat coming from objects such as hair dryer, body, etc, and has now been remodeled by Hargather for the presentation of sound waves, according to his report NPR.
It is important to remember that sound is a change in air density or a compression wave moving forward at a speed of up to 1.225 kilometers (761,2 miles) per hour.
SFV can detect how far these waves travel through air at different densities, just as it can detect the same with light. However, a photo machine high resolution is necessary due to the extreme velocities of the compressional waves.
In the following video, you can see how the sound waves appear from the dropping of a book, and from other daily sounds, such as those produced by clapping or when we grab a towel, but also from more sophisticated ones such as a gun shot, firecracker explosion etc .
Note: This video has English subtitles, but you can translate these subtitles by clicking the "Subtitles" button at the bottom right of the video. Then press the arrow to open the box with multiple options and select "Subtitle Translation", and finally in the new window that will appear press the arrow and move the bar to the right until the option "Greek". Select it and watch the video with Greek subtitles.
http://www.youtube.com/watch?v=px3oVGXr4mo
