# Music streaming services - data compression using the example of songs

In the workshop on data compression using the example of songs, students discover how to reduce the storage space of music. In the past, you could play about 30 minutes of music per page with one long-playing record. Then the CDs were developed, which can play about 80 minutes of music. The development of the mp3-compression method was groundbreaking. On a mp3-player with a capacity of one gigabyte you could store more than 540 minutes, that is 9 hours of music. Even more advanced were the music streaming services, which manage to provide the complete world of music with very little data volume. How is it possible that playing and storing music requires so little storage space or so little data?
In the course of the workshop, students learn how music is presented on the computer. Afterwards, they work out their own criteria for a compression method and apply it themselves. At the end of the day they can compress a selected song using their own method. The guiding question is always: How much compression can I do so that there is still good quality?
Among other things, students will have to test their own hearing to develop criteria for compression. Thus, at the end of the module, different procedures may be available and the results compared. In this context, subject-specific skills from the fields of analysis and trigonometry will be encouraged.
Since the difficulty of the module can be varied, classes from grade 9 on can participate in this CAMMP day. For upper level courses the level is adjusted accordingly (see below).

Duration: from 5 hours (incl. lunch break)
Contents: Functional equations, trigonometric functions
Previous knowledge: functional concept
Participants: Mathematics courses from grade 9 upwards
Created by: Jonas Kusch, Lars Schmidt
Registration: Appointments can be arranged individually by e-mail.

## Workshop for upper level courses

The structure of the workshop is the same as that for the younger students, as explained above, but the Fourier analysis is discussed in more detail with the upper level school students. The students perform the change between time and frequency space themselves through matrix multiplications and independently apply their listening model in the frequency space by cutting off the frequencies they cannot hear.
The workshop for the upper school can be used as a motivation or application of matrices, as they see the workshop as a use in their everyday life.

Duration: from 5 hours (incl. lunch break)
Contents: Functional equations, trigonometric functions, matrices, vectors and their multiplication
Previous knowledge: concept of functions, vectors, matrices (if possible)
Participants: Mathematics courses from grade 11 onwards
Created by: Jonas Kusch, Lars Schmidt, Kirsten Wohak
Registration: Appointments can be arranged individually by e-mail.