Natural freq and Helmholtz Resonance notes

Natural Freq.

-a sound wave is created as a result of a vibrating object. The vibrating object is the source of the disturbance that moves through the medium.
-The frequency or frequencies at which an object tends to vibrate with when hit, struck, plucked, strummed or somehow disturbed is known as the natural frequency of the object
-If the amplitudes of the vibrations are large enough and if natural frequency is within the human frequency range, then the vibrating object will produce sound waves that are audible.
-The quality or timbre of the sound produced by a vibrating object is dependent upon the natural frequencies of the sound waves produced by the objects.
-the speed of sound waves within the air column is not alterable by the musician (they can only be altered bychanges in room temperature), the length of the air column is. 
-To conclude, all objects have a natural frequency or set of frequencies at which they vibrate when struck, plucked, strummed or somehow disturbed. The actual frequency is dependent upon the properties of the material the object is made of (this affects the speed of the wave) and the length of the material (this affects the wavelength of the wave). 

Helmholtz Resonance
-Helmholtz resonator is a container w/ gas and an open hole
-Ex. of Helmholtz resonators/oscillators or imitate: guitar bodies, whistles, empty bottle
-"The resonators that Helmholtz described performed an incredible feat. When sound would hit the (a) opening, the vibrations would excite the volume of air in the body of the resonator. However, because of its peculiar design, the resonator would only transfer and amplify a single tone to the (b) opening, but only if that tone was present in the sound being made. The volume of the body determined which tone was transferred.

-"Helmholtz had many resonators of different sizes and shapes. In fact, any rigid structure containing a volume of air connected to the outside via a small opening (hole, port, or neck) that amplifies a particular frequency can be considered a Helmholtz resonator. A very common object that classifies is a standard beer bottle. When a person blows across the top of an empty bottle, a low oo (as in tool) can be heard. Regardless of how hard or soft the person blows, the same note is created, just louder or softer." 

https://www.youtube.com/watch?v=PZVeJ2rh6ts