In this science experiment, we will build a didgeridoo, a type of wind instrument that produces a specific base frequency, and understand how various modifications affect the sounds it makes. We will apply principles of acoustic physics to predict the correct length of the instrument needed to achieve the desired frequency and then test these predictions by building and playing several didgeridoos.
In simpler terms, we will try to figure out how to build a didgeridoo that makes a specific musical note (base frequency), and how different changes to the instrument and the way it’s played can change the sound it makes.
Aim
The aim of this experiment is to build a didgeridoo capable of producing a specific base frequency, and to observe how various modifications and playing techniques impact the sounds it produces.
Theory
1. In acoustics, the sound produced by a closed tube (like a didgeridoo) depends on its length and the speed of sound. The base frequency, or fundamental frequency, can be determined by the formula:
Length = Speed of Sound / 4(Base Frequency)
This forms the theoretical underpinning of our experiment. In addition, changes to the shape or structure of the tube and the technique used to play it are also expected to impact the sound produced.
2. The wind instrument that produces a continuous drone by playing with continuously vibrating lips, using a special breathing technique which is known as circular breathing, is called the didgeridoo. This is commonly available in two shapes, conical or cylindrical, and can be 1 to 3 meters long.
3. Longer the instrument, the lower will be its pitch.
Requirements
1. 2 Inch PVC pipe
2. Frequency Generator
3. Heat gun
4. Computer Program (Amadeus II)
5. Notebook
Procedure
Step 1: Construct a set of six digits ranging in frequency from 110 hertz to 51 hertz with the help of 2 inch PVC pipe and fittings by adding different lengths of tubing to a 110-hertz base unit.
Step 2: To verify prediction, create a seventh didge for the set and two more identical single-piece didges, having a specific 65.4-hertz frequency.
Step 3: Modify the two identical didges with grooves, bends, dimples, and an end bell using the heat gun.
Step 4: Analyze the sound spectral of each didge by using a computer program (Amadeus II).
Step 5: Record your data in a tabular form for observation.
Observation
1. On verification, we find that the observed harmonic frequency of my didges was consistent with the closed-end tube acoustic model.
2. Our equation, Length = Speed / 4(base frequency), has depicted the length of didge to within 2% for a range of measured base frequency.
3. Didges of 65.4-hertz base frequency were created successfully by cutting tuning to the predicted length.
4. Frequency is increased by modifying a first bend, an end bell, and a very hard blowing technique; on the other hand, the second bend decreases frequency.
5. The sound pattern of harmonics in didges was influenced by the subtle difference in playing techniques more than by specific modification.
Results
They found that the physics predictions were pretty good at guessing the right length for the instrument, but that the sound it makes also depends a lot on the skill and technique of the person playing it.
1. We build a didge with desired frequency.
2. A number of harmonics combined together to compose a total didge sound.
3. In spite of being a simple ancient musical instrument, the didgeridoo produces a complex sound.
Precautions
1. Construct the didges carefully.
2. Make sure that didges do not have any kind of error.
Conclusions
In this experiment, using the acoustic principle of physics, we have created a didgeridoo musical instrument with a specific base frequency. And analyzes the harmonics that create the total musical sound.
VIVA Questions with Answers
Q.1 What was the aim of your experiment?
ANS. To create a Didgeridoo with desired base frequency and determine how the total sound produced is being affected by the modification and playing techniques.
Q.2 What do you understand about the musical instrument didgeridoo?
ANS. This wind instrument produces a continuous drone by playing with continuously vibrating lips, using a special breathing technique which is known as circular breathing.
Q.3 Which equation did you use in this experiment?
ANS. We used Length = Speed / 4(base frequency). It has depicted the length of didge to within 2% for a range of measured base frequency.
Q.4 How did you increase the first frequency of Didgeridoo?
ANS. Frequency is increased by the modification of a first bend, an end bell, and a very hard blowing technique.
Saquib Siddiqui is a Mechanical Engineer with expertise in science projects and experiments. Saquib’s work focuses on integrating scientific concepts with practical applications, making complex ideas accessible and exciting for learners of all ages. In addition to his practical work, Saquib has authored several articles, research papers, and educational materials.
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