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

Another Possible Experiment

Today, we looked into more experiments that we could possibly do for our project. This is the most recent development.

Possible Experiment:

Question: Will a higher frequency of sound have a greater force?

Hypothesis: Yes, because the greater repetition in a higher frequency will have a greater effect on the velocity, which will in turn increase the acceleration, therefore increasing the amount of force.

Materials Needed:

• a wooden dowel
• two 1.5 liter bottles ✓
• two rubber bands ✓
• a needle ✓
• a table clamp
• recording device (and/or a tone generator) ✓
• speaker ✓
• timer ✓

Procedure:

1. Blow into the bottle and record the sound that comes out.
2. Using the rubber band, attach one bottle to each end of the dowel.
3. Put the needle in the clamp and clamp it to the edge of a table.
4. Balance the dowel on the needle.
5. Place a speaker beneath one of the bottles.
6. Play the recorded sound.
7. Record results (time, rpm, acceleration, etc.).

Possible Variations:

Will the physical properties (surface area and mass) of the object being moved affect its velocity?
Will volume affect velocity? Higher = faster, lower = slower? (or the larger the sound, harder the vibrations can enter and move the bottles)

Will temperature affect rpm? Hot = slower, colder = faster b/c sound waves moves faster in colder temperatures.

We hope this draft is usable for our final project. Wish us luck!

-The PhysicsTreeStinger Crew

(Annelise, Melanie, Colin, and Dominic)

Experiment Ideas

First Draft of Our Experiment

Question: What can sound move? Can we see it move? How much force does it exert on the object?
   Independent Variables: temperature, substances.

Hypothesis: Objects will move farther in warmer temperatures because air particles are able to move more freely in higher temperatures. Objects that are lighter have less mass and therefore require less force to move, so light objects will also move farther.

Experiment:
   Materials Needed:

• water
• a pot
• a burner 
• speaker system
• string
• wooden block
• thermometer 
• meter stick
• feather
• dry ice

   Procedure:

• Place the object (steam, dry ice, or feather) to be moved in front of the speaker
• Turn on the speaker
• Measure how far it moves
• Record data

Data: none so far

Conclusion: none so far

Today in class, we did more research and found that the speed of sound depends on temperature. We created a rough draft of our experiment. The independent variables will be the temperature and type of object we are trying to move. The dependent variable is the distance that sound can move the object in a certain amount of time. We wrote out a procedure and we will be revising our plan next week if necessary.

-The PhysicsTreeStinger Crew

(Annelise, Melanie, Colin, and Dominic)

Links for Research

Links for Research:

As the first stage of our physics project, our group will be researching the many properties of sound and light and their complex relationship. We have compiled a list of articles that might be useful and their URLs.

https://www.youtube.com/watch?v=px3oVGXr4mo

What Does Sound Look Like (fire/heat)

https://www.youtube.com/watch?v=4shodbQMcmM
What Sound Looks Like (under corn starch and water)

http://www.physics.org/article-questions.asp?id=45
What is a mirage

The Special Relationship Between Sound and Light Article

http://www.studyphysics.ca/newnotes/20/unit03_mechanicalwaves/chp141516_waves/lesson49.htm
Properties of Sound

http://www.life.umd.edu/faculty/wilkinson/bsci338/ACL2_sound.pdf
Properties of Sound

New link!
Possible Project Idea

http://people.seas.harvard.edu/~jones/cscie129/nu_lectures/lecture3%20/ho_helmholtz/ho_helmholtz.html
Helmholtz Resonators

http://newt.phys.unsw.edu.au/jw/Helmholtz.html
Helmholtz Resonance

We will be reviewing these articles throughout the week and will post our research findings on the next A-day.

-The PhysicsTreeStinger Crew
 (Annelise, Melanie, Colin, and Dominic)