Supervision: Hervé Lissek

Project type: Semester project (bachelor) Semester project (master)

Available

The Corona Discharge (CD) principle has been demonstrated to allow achieving linear acoustic flow velocity source without relying on an intermediate membrane, presenting an almost perfect electroacoustic transduction with an extremely sharp impulse response. The CD loudpeaker generally consists of two electrodes, a "corona" electrode of extremely thin size (array of wires, needles, etc.) put at a sufficiently high voltage to ionize the surrounding medium particles, and a "collector" electrode, conductor of larger size than the "corona" connected to the ground, attracting the ions while being sufficiently transparent to particle streams (eg. a metallic grid).

With this configuration, the CD loudspeaker presents a combination of two intrinsic sources: a monopolar "Heat" source, due to the local heat exchanges occurring in the ionization process, and a dipolar "Force" source, resulting from the electrostatic force accelerating the charged particles (and the surrounding medium) back and forth around the transducer. This transducer has been proven to be an ideal flow velocity source, and a recent PhD thesis proposed a detailed model of the transducer that can serve now for further optimization.

The absence of membrane allows for a fully transparent sound source, which could be an asset in certain circumstances: for example, most of the headphones/earphones owner suffer from the so-called "occlusion effect" that is likely to create a low-pass effect on the sound rendering. With a fully open configuration, the rendered sound is likely to be more natural. But the price to pay is a strong leakage of sound towards the environement, which needs to be taken in consideration and worked around.

The proposed semester project intends to work on simulating and eventually implementing a fully open CD headphone, and testing it on an artificial ear facility.

The project will consist in the development of a COMSOL (and/or analytical) model of the transducer(s), that will serve for geometry optimization. After defining a set of optimal geometries, one or several prototype(s) will be constructed and tested in anechoic conditions.

Content

• COMSOL and/or Matlab simulations
• Electroacoustic measurements

Prerequisite

• BA5-Electroacoustique
• or MA1-Audio Engineering