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Some early considerations
The main aim with this musical toothbrush project is to combine the action of brushing one's teeth and playing music such that the user gets the impression of being able to control/interact with the music depending on how he/she brushes his/her teeth. Thus it seemed important to us to start very early with a rather simple prototype in order to have the time to develop a fitting mapping from the tooth brushing movements to the music.

This early prototype was a simple toothbrush, augmented with an accelerometer and connected to a computer with a serial cable. The accelerometer is the sensor that we use to trace the movements of the toothbrush. More precisely, it is a 2-axis-accelerometer that permits us to sense how fast one moves (“accelerates”) the toothbrush. This prototype was our main development prototype throughout the whole Software Design Phase, and it looks as follows:

Our first prototype

Besides the accelerometer, we considered a lot of different sensors such as a pressure sensor, a microphone, a tilt switch, or a light sensor. But after different tests and discussions we decided to go for the accelerometer and to put the other sensors to “future work”.

Interaction between the tooth brushing movements and the music
We finally came up with having two different ways of influencing the music being played while one is brushing ones teeth. First the music adjusts itself to the tempo of the tooth brushing movements, i.e. if one brushes faster, the music also speeds up, and if one brushes slower, the music also slows down. The second way of influencing the music is the orientation in which one holds his/her toothbrush; compared to if one is brushing the front of his/her teeth, thus holding the toothbrush horizontally, one will get an octave higher if brushing the upper teeth (i.e. holding the brush upwards), and one octave lower if brushing the lower teeth (i.e. holding the brush downwards).

Choosing the desired music
After having analyzed the conventional process of brushing one's teeth, we found that the most implicit way of choosing the music is if it each toothpaste tube is associated with a different kind of music. To illustrate this concept, we designed eight different toothpaste tubes, each of them representing a different genre of music. Thus when shopping in a supermarket, you would be presented a range of toothpastes as follows:

Eight toothpastes that we have created.

Associating one music genre to one toothpaste did we achieve by augmenting each of the above toothpastes with an RFID tag that will be detected by the toothbrush whenever the toothpaste comes close to the toothbrush head. Once toothpaste has been applied (i.e. brought close to the toothpaste's head), the system starts playing back the corresponding music: Christmas, Animal, Pop, or Disney songs are examples of categories that could be offered.

Forcing the tooth brushing duration or not?
A question that arose when developing the prototype was what should happen when one song has finished. Should we fix the duration of time during which music is played, in order to force the users to brush their teeth for a certain duration, or should we leave it up to the user how long/short he/she likes to brush his/her teeth? Our current implementation plays all available melodies of the chosen category in a queue, one after the other, until the reset button is pressed. The reset button is located on the toothbrush and is used to stop the playback of the currently played music. After the actuation of this button, the user can apply another toothpaste to obtain a new category of melodies.