Hello, world. This is Shelby Beckstead, and this is my second labor!
Have you ever walked down a long hallway and heard your footsteps echo? You can hear echoes from a variety of everyday objects such as walls, corners, caves, or even forest groves. So what exactly is an echo? According to The Flying Circus of Physics, “A standard echo is merely the reflection of sound waves back toward the origin of sound.” But what happens when a host of echoes are produced? If the echoes are close enough, you can actually hear them as a musical note.
Imagine walking through a grove of trees hearing a high frequency sound, and low frequency sound. The high frequency sound could be a women’s scream, and low frequency sound could be a roar. While the women’s scream gives a fine echo, the low roar might not even give an echo. The Flying Circus of Physics says that in a forest, “If you sing a musical note, the echo is an octave higher, (that is, has frequency twice what you send out.)” You may be asking, why does a grove of trees give such specific echoes?
According to ConneXions, sound reflects off certain objects, but the sound that it makes depends on the wavelength of the sound. “When the wavelengths are all larger than the object, a smaller wavelength reflects better than a longer wavelength.” (Walker, Jearl) If you clap your hands and send out a range of wavelengths, the smaller wavelengths corresponds to a higher frequency, and reflects better from a grove of trees for example. Thus, low frequencies sometimes give no echoes.
A musical note has two components; a lower frequency and a frequency that is twice as much as the original. When you project a noise, the echo is dominated by the frequency that is twice as much. Therefore, the echo is primarily at twice the original frequency.
Forest groves are a good example of many different echoes reflecting back to you while you walk through the forest. Some low sounds don’t make an echo, while high pitched noises reflect smaller wavelengths. Now you know why echoes can be so specific!
Schmidt-Jones, Catherine. “Frequency, Wavelength, and Sound.” ConneXions. Ed. Catherine Schmidt-Jones. N.p., 11 Oct. 2011. Web. 25 Oct. 2011.
Walker, Jearl. “Echoes from walls, corners, and forest groves.” The Flying Circus of Physics. 2nd ed. 1975. New Jersey: John Wiley and Sons, 2007. Section 3.64. Print. This is where the definition of an echo was provided. Also, it introduced the question of why echoes are so specific.
Willis, Bill. “Echo Echo Echo Echo Echo.” What Make’s an Echo? Wonderland Website Design, 2011. Web. 25 Oct. 2011.