What exactly is sound?

By | April 5, 2021

Interesting as a thousand Christians! I can almost see the organ pipe and the water-insulated compressor in front of me :)

When we are still in Sabine, we can continue a little in general about sound and what it really is.

So, what is sound really? Well, you can easily explain sounds as mechanical waves that propagate in solid materials, liquid or gas. What we normally perceive as sound is when these wave motions propagate in the air (gas) and form pressure variations which then set our eardrums in motion. Here you see the oscillating movement that occurs and presses the air molecules in front of it http: //www.acs.psu.e…wavemotion.html

So what is it that makes sounds sound different? There are actually two things, frequency measured in hertz (Hz) and volume (amplitude) measured in decibels. Frequency measured in Hertz is equal to the number of oscillations per second and is also equal to the pitch of the sound. The more oscillations per second, the higher the frequency / tone, it simply becomes. That we experience that the tone A 440 Hz sounds different on different instruments depends on the harmonics that the specific instrument generates. We will return to that a little later.

With Sabine’s sound experiments fresh in our minds, we can also look at what really happens when the sound from his organ pipe hits the room-separating surfaces (floors, walls and ceilings) in his experiments. When the sound from the organ pipe has traveled through the air and finally hits, for example, the ceiling, some of the sound will be absorbed by the material in the ceiling, some will be reflected back in the room and some of the sound will go completely sonic straight through the ceiling. The properties of the building materials here determine how much of the energy of the sound waves is absorbed, respectively reflected or passes straight through. In the future, we will take up some different materials and construction techniques as practical examples of this.

As Christian wrote, sound absorption is defined as the product of a surface and an absorption factor, which means that the sound absorption for a closed room = the sum of the absorption of the room’s delimiting surfaces where different building materials exhibit different absorption factors. The air also has a certain absorption, especially at high frequencies, but it is usually not taken into account when calculating in smaller rooms. Thought to go through a little more about sound absorption in the next post.

Hejja // Björn :)

Source:studio.se