Bekah+Johnson+and+Bailey+Meiner+-+Acoustics

The Effect of Sound Frequency on the Size of Acoustic Shadows

Problem

How does the frequency of a sound effect the size of its acoustic shadow?

Background Research

Acoustics is the physical science “devoted to the study of the production, transmission, and reception of sound” (Schlager 311). An “acoustic shadow” is the area in which a sound wave is partially or wholly blocked by an object. One phenomenon in acoustics, called diffraction, is the ability of sound waves to bend around an object, changing the size of this acoustic shadow. The range of sound audible to human ears includes frequencies as low as 20 Hz and as high as 20 kHz (Schlager 255). “The ability of a sound wave to diffract decreases as frequency rises and wavelength shrinks” (Gregersen 16). Thus, within the audible range, there would be a significant change in the size of these acoustic shadow. Several practical applications of this study exist. Near roadways, barriers are used to separate the sound of the vehicles on the highway from the surrounding areas. An understanding of the frequencies produced on a highway combined with an understanding of acoustic shadows would make it possible to determine the height that these barriers would need to be to effectively block the sound. Other practical applications exist in music and several other areas.

This is absolutely jammed packed with information, but I don't think you need the part, "The range of sound audible to human ears includes frequencies as low as 20 Hz and a high as 20 kHz". It doesn't really have to do with your project. - Abby Shute How does the frequency relate to the acoustic shadow as far as increasing and decreasing? -Monica Dentino

Hypothesis

If the frequency of a sound is increased, then the size of its acoustic shadow, cast by a set object at a set distance, will increase. You might want to put more numbers into your hypothesis, like increase by blank amount. -your favorite: Noah Hahn

Materials

Total: $56.27
 * 1 tuner with a sound out function $20
 * 1 50 cm x 50 cm square piece of plywood $6.27
 * 1 decibel meter $23
 * 1 measuring tape $7

Methods

1. From a height of 1 meter, set the tuner to emit a frequency. 2. At a height of 1 meter, measure the volume with the decibel meter at half meter increments until ten meters is reached. 3. At a distance of one meter from the tuner, suspend the square piece of plywood so that its center is level with the tuner. 4. At a height of 1 meter, measure the volume with the decibel meter at half meter increments until ten meters from the tuner is reached. 5. Repeat steps 1-4 with different frequencies, both of higher and lower pitch.

Be more specific about what frequencies you are going to use. Remember this should be reproducible by anyone. Ms. Miller Do you need to include instructions for using any of this equipment? Ms. Miller What units are you using to measure the data? Ms. Miller

Are you planning to do this at school? It sounds like you may need to find a way to control outside noises for accuracy -Monica Dentino

__Bibliography:__

"Acoustics." Science of Everyday Things. Ed. Neil Schlager. Vol. 2: Real-Life Physics. Detroit: Gale, 2002. 311-318.Gale Virtual Reference Library. Web. 18 Oct. 2013.

"The Decibel Scale." The Britannica Guide to Sound and Light. Ed. Erik Gregersen. New York: Britannica Educational Publishing with Rosen Educational Services, 2011. 6-7. Physics Explained. Gale Virtual Reference Library. Web. 18 Oct. 2013.

"Diffraction." The Britannica Guide to Sound and Light. Ed. Erik Gregersen. New York: Britannica Educational Publishing with Rosen Educational Services, 2011. 15-17. Physics Explained. Gale Virtual Reference Library. Web. 25 Oct. 2013.

"Sound Waves." The Gale Encyclopedia of Science. Ed. K. Lee Lerner and Brenda Wilmoth Lerner. 4th ed. Vol. 5. Detroit: Gale, 2008. 4019. Gale Virtual Reference Library. Web. 18 Oct. 2013.

"Wave Motion." Science of Everyday Things. Ed. Neil Schlager. Vol. 2: Real-Life Physics. Detroit: Gale, 2002. 255-262. Gale Virtual Reference Library. Web. 18 Oct. 2013.I

I would almost have possibly one to two more cited sources, maybe. - Abby Shute