© 2019 by Pernille Dahl & Cole Robbins. 

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Chirping Bird w/ Cuica

Parts needed:
  • 1 Model

  • 1 Large file folders

  • 1 Straw

  • 2 Bamboo skewer  

  • 1 Bottle cap, metal

  • 2 Pins

  • Palitos de paleta

  • String

Extra Tools: 
  • 2 staplers with staples

  • 2 Hole punchers

  • Hammer and large bolt to flatten bottle cap

  • Drill

  • Drill platform

  • Nail bit for drill (several)

Project Description:

A bit more info:

The chirping bird and cuica make sound in a very peculiar way.  The slip/stick motion of the pin tip scratching along the bottle cap is very similar to that of the wet paper on the string, chalk screeching on a chalkboard, a violin bow on violin strings and tectonic plates sliding beside each other.  There is a period of no motion as tension builds up, then a period of great motion as the two items move to a low-energy state, then a return to the slow build up of motion.  With earthquakes, this takes years, decades or millennia.  With a violin, the process happens many times per second. 

 

In both the bird and cuica, the sounding board principle is important.  On the cuica, try holding the string alone, and pulling down on the wet paper.  The sound is there, but much less intense.  The cup then helps to connect the vibration from the string to the air – it actually pushes on more air than the string, and sends out sound waves with much more energy than just a vibrating string.  This is one reason behind the big box of a guitar, and the reason real cuicas (very loud!) are as large as big drums.  A bird made with a large body may be louder, because the body of the bird is the sounding board for the tiny vibrating pin. 

 

The bird may also be louder if made with two pins.  If you make the tail very small, not much air hits it as it flies, so it may not have enough force to spin the bottle cap around.  A nice big tail works better.

Concepts:

  1. Sound is created when vibration occurs.

  2. The pin does not move smoothly on the fender washer – they rub together in a slip/stick motion common to bowed instruments and tectonic plate movement. 

  3. In the Cuica, the paper moves on the string the same way.

  4. The volume of a given sound depends on various things including its size and how it connects to the air around it.

Questions:

  1. How does the bird make noise?

  2. How could you make the bird louder?

  3. What would happen if you made a very small tail?

  4. What do you think would happen if you made the cuica out of a big drum?