The Experienced, the Novice, & the Musically Illiterate

We set out to analyze the sound produced by a didgeridoo when played by an experienced didgeridoo player (Bryant), a woodwind player without didgeridoo experience (Matthew), and a piano player without any wind instrument experience (Anna). We found that Bryant produced two distinct frequencies one one fluctuated slightly around 293Hz (the musical note D) and the other around 349Hz (the musical note f). Bryant was able to produce a nearly constant frequency on the didgeridoo because he was able to maintain constant airflow and steady embouchure due to his expertise. Matthew's frequency fluctuated in between the range of 261Hz up to 329Hz (between the musical notes C and E). His frequency fluctuated greatly and he was not able to make the instrument resonate distinctly at its fundamental frequency. Lastly, we were not able to obtain a measurement for Anna's frequency because the sound frequency fluctuated too greatly; this is probably due to her lack of wind instrument training with the didgeridoo. Here are results:

A Real Didge Player

We interviewed an experienced didge player, Northwestern junior Bryant Smith.

Crocodile Copley

After finding this video on YouTube, our group was curious as to how difficult running and playing two didgeridoos would be. Bryant Smith helped us to understand the level of difficulty.



As seen on the video, Bruce Copely really enjoys running with the didgeridoo. Thus, Bruce Copely sets out on his daily run with the didgeridoo that emits a whine of 256 Hz. He is running at a speed of 10 miles per hour (4.47m/s) and he overtakes a lady who is strolling at a speed of 2 miles per hour (0.89 m/s). What is the frequency observed by the lady walking when Bruce Copley is approaching her from behind, and what is the frequency observed by the lady walking after Bruce Copley passed her?

Before Copley passes her we would use the equation:
f(obs)=f(source)[(1-vobs/vsound)/(1-vsource/vsound]

f(obs)=256[(1-0.89/343)/(1-4.47/343)]

f(obs)= 258Hz

After Copley passes her we would use the equation:
f(obs)=f(source)[(1+vobs/vsound)/(1+vsource/vsound]

f(obs)=256[(1+0.89/343)/(1+4.47/343)]

f(obs)=253Hz

Principles to Note: the before observed frequency is going to increase whereas the after observed frequency is going to decrease in comparison to the actual source frequency.


Just in case Copley ever comes across any dangerous crocs while he is running, he knows exactly what to do with them....

Didgeridoo Sound Perception in the Ear

As sound approaches the ear, the pinna, the visible part of the outer ear, amplifies and directs it through the auditory canal. As sound moves through the auditory canal, it eventually hits the tympanic membrane, which is a thin membrane at the end of the auditory canal. The sound causes the tympanic membrane to vibrate at a frequency that is directly proportional to the frequency of the sound waves. The kinetic energy of the vibrating tympanic membrane is then transferred by the ossicles, three connected bones known as the malleus, incus, and stapes, through an area called the middle ear. At the base of the stapes, the last in the series of ossicles, there is a footplate that presses against the oval window, which is a small membrane on the surface of the cochlea. The large difference in surface area of the tympanic membrane and the smaller oval window results in an amplification of the sound signal at a ratio of 14:1. As the ossicles vibrate, the footplate vibrates the oval window, which causes wavelike motion in the cochlear fluid. The wave motion of the cochlear fluid bends the stereocilia of the hair cells. The bending of these stereocilia is what accounts for the conversion of the mechanical signal of the pressure waves in the cochlear fluid to the electrical signal in the form of action potentials in the auditory nerve.



The stereocilia are positioned in a series of lines within the Organ of Corti. The stereocilia are connected to their neighbors by tip links, which are protein structures resembling the links of a metal chain. The ends of the tip links are connected to potassium ion channels embedded in the membranes of the stereocilia of the hair cells. When the stereocilia are bent, the tip links cause the potassium ion channels to open resulting in an influx of ions into the stereocilia. Subsequently, the influx of ions results in a change in the electrical potential across the cell membrane and eventually the depolarization of the cell, which leads to an action potential in the auditory nerve.

The transfer of information from sound waves in the air to perception in the brain is an extraordinary process. Information conversion takes place throughout this process from the airwaves that make up sound to the mechanical waves of the tympanic membrane and ossicles to fluid waves of the cochlear fluid to electrical signals in the hair cells and the auditory nerve. The auditory nerve then takes this signal to the auditory cortex in the brain, which processes these sounds into cognitive signals of what we hear and perceive.

Didgeridoo Sound Travel Through Air

Sound is a longitudinal wave because it moves air molecules (or the medium that it is moving) in the same direction that it is traveling. Therefore, the density of air molecules increases and decreases. Areas of high pressure and high density are considered condensation and low density and low pressure areas are called rarefaction. Areas of rarefaction are considered the wave troughs and areas of condensation are wave peaks. Therefore, regions of condensation are separated by a full wavelength as are regions of rarefaction. The speed of sound depends on the medium through which it is traveling. Sound generally travels fastest in solids because solids are generally stiffer than gases and therefore provide a larger restoring force and acceleration. The speed of sound in a gas is dependent on temperature, and at room temperature the speed of sound is approximately 343 m/s.



The frequency of sound is infinite. However, the human ear can only hear sounds between the frequencies of 20-20,000Hz. Infrasonic sounds occur at smaller frequencies than the human ear can hear and ultrasonic sounds occur at larger frequencies than the human ear can hear. A sound wave is a pure tone if is is a single frequency. Most sounds are some combination of pure tones and many sounds – especially in music – are combinations of pure tones that are harmonically related. The term pitch is used to describe the combination tones.

Didge 2.0: Modern Uses

Modernized versions of the didgeridoo have been developed. The most well-known of these is the didjeribone, which is similar to a plastic cross between a trombone and a didgeridoo. A keyed didgeridoo was also developed in the late twentieth century by Grahm Wiggins at the physics workshop of Oxford University.

Use of the didgeridoo has spread to modern Celtic music as well as the experimental and avant-garde music scene. Industrial bands have also began using didgeridoos in their music to link ecology to industry. Instrumentalists have begun experiementing with the various uses of the didgeridoo, applying techniques from other genres of music such as beatboxing, which can be seen in the clip below.



A 2005 study by the British Medical Journal found that the didgeridoo may be beneficial in reducing snoring, sleep apnea, and daytime sleepiness in those who play these instruments. Playing the didgeridoo strengthens the muscles in the upper airway and thus reduces their tendency to collapse during sleep.

The Didgeridoo Dissected: Historically & Mechanically

Quick Facts:

The didgeridoo is claimed to be the world’s oldest wind instrument, dating back to over 2000 years ago in the form of cave paintings in the Northern Territories of Australia. The didge is a wind instrument of the Indigenous Australians of northern Australia. The didgeridoo is cylindrical or conical in shape and the average length is about 1.2m. The longer the instrument is the lower the pitch will be, and keys from D to F# are preferred.

Brief History

The name used by the actual aborigines for this instrument is Yirdaki. This varies slightly from region to region. The didgeridoo was most known in eastern Kimberley and the Northern Territories of Australia. It wasn’t until the trade infrastructure was strengthened that the didgeridoo became more available all across Australia and began to interest non-aboriginal people. In 1963 the first non-aboriginal didgeridoo recording was made.


Mechanics



Didgeridoos are made from the trunks or substantially large branches of hardwoods, particularly the various eucalyptus species of the native region. The optimal tree is one which has been hollowed out by termites to the right degree, the hollow can’t be too big or too small. A termite-bored didgeridoo has a hollow that increases in diameter towards the bottom. An aboriginal didgeridoo maker tests the tree by removing a small piece of bark and hitting the tree to hear if the sound indicates a hollowness. This allows its resonances to occur at frequencies that are not harmonically spaced in frequency. The bark is removed, the ends are trimmed, and, if preferred, beeswax may be applied to the mouthpiece.

The didgeridoo is played by a special breathing technique known as circular breathing, in which the instrumentalist breathes in through the nose while expelling the air simultaneously through the mouth. This allows the instrumentalist to play the didgeridoo without having to stop to replenish their air supply. Well practiced didgeridoo players can play continuously for more than 40 minutes.

Cultural Role



The didgeridoo most often accompanies dancing and singing in religious ceremonial rituals of the aboriginal groups of Northern Australia. Men are the usual players of the didgeridoo, although there are some female didgeridoo players they can only play in informal contexts and are not encouraged to do so. Before modern technology came to be the didgeridoo was also used as a means of communication. Some of the sound waves from the instrument could be perceived across far distances through the ground. Each player had his own base rhythm that allowed him to be recognized by the listener.