Electroacoustic music | EPFL Graph Search

Electroacoustic music is a genre of popular and Western art music in which composers use technology to manipulate the timbres of acoustic sounds, sometimes by using audio signal processing, such as reverb or harmonizing, on acoustical instruments. It originated around the middle of the 20th century, following the incorporation of electric sound production into compositional practice. The initial developments in electroacoustic music composition to fixed media during the 20th century are associated with the activities of the Groupe de recherches musicales at the ORTF in Paris, the home of musique concrète, the Studio for Electronic Music in Cologne, where the focus was on the composition of elektronische Musik, and the Columbia-Princeton Electronic Music Center in New York City, where tape music, electronic music, and computer music were all explored. Practical electronic music instruments began to appear in the early 20th century. Musique concrète Tape music is an integral part of musique concrète, which uses the tape recorder as its central musical source. The music can utilise pre-recorded sound fragments and the creation of loops, which can be altered and manipulated through techniques such as editing and playback speed manipulation. The work of Halim El-Dabh is perhaps the earliest example of tape (or, in this case, Wire recording) music. El-Dabh's The Expression of Zaar, first presented in Cairo, Egypt, in 1944, was an early work using musique concrète–like techniques similar to those developed in Paris during the same period. El-Dabh would later become more famous for his work at the Columbia-Princeton Electronic Music Center, where in 1959 he composed the influential piece Leiyla and the Poet. Composer John Cage's assembly of the Williams Mix serves as an example of the rigors of tape music. First, Cage created a 192-page score. Over the course of a year, 600 sounds were assembled and recorded. Cut tape segments for each occurrence of each sound were accumulated on the score.

Compensation des non-linéarités des systèmes haut-parleurs à pavillon

Delphine Bard

The assumptions of linearity and autonomy assumed in circuit theory are known to be respected only partially by electroacoustic transducers. In particular, the dynamics range of the latter is limited by the audible nonlinear effects that they are causing. In the domain of active noise control, the distortion products limit noise reduction performance. The present thesis work stems from characterization of these observations. We want to design a real-time system compensating the nonlinearities of electroacoustic devices. The first part of this report concerns the nonlinearity effects. It is shown that the use of classical characterization methods of an electroacoustic device (harmonic distortion, intermodulation, frequency difference ...) is limited. Hence, they can not be used to determine the nonlinearity laws themselves, but rather only their effects for arbitrary excitations. First, a method based on multitone harmonic excitations has been proposed and validated. It has been applied for the characterization of loudspeaker prototypes using several different technologies, which are used for active noise reduction in an aircraft turboreactor. The second part of this work addresses the elaboration and validation of a nonlinearity effect compensation method. This method is based on the description of the nonlinearities by the Volterra series. For this, we need to place an upstream system, characterized by the inverse nonlinearity law of the loudspeaker system. After having determined precisely the Volterra kernels of the system to be characterized, the kernels of the upstream compensation system are determined by assuming that their cascade obeys to a linear law. For this purpose, a kernel measurement method in the frequency domain has been developed, validated and tested. Since we are concerned with loudspeakers, we took their flying time into account. The compensation method has been validated by computing the simulated response of the compensation circuit. Resulting analog signals have then been applied to the loudspeaker. Measured performances fulfill the expectations. In the last part, the compensation method has been applied in a real-time Digital Signal Processing) DSP controller, which allowed to realize a demonstrator to the implemented for future industrial applications.

EPFL2005

Compensation des non-linéarités des systèmes haut-parleurs à pavillon

Delphine Bard

EPFL2005