Supervision: Hervé Lissek
Semester project (master)
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.
This transducer is also well suited for active noise reduction application, and unprecedented sound absorption performance has been achieved in a laboratory condition, with the plasma sound absorber at the end of an impedance tube, in a closed configuration (transdcuer backed with a small air-filled cavity). The aim is to evaluate the performance as a "liner" along a duct, leaving the duct open while reducing the noise.
The proposed semester project intends to develop a wall mounted prototype of active plasma sound absorber with application to ducted noise reduction, with a preferred embodiment being a ring of plasma absorber place at some position along the duct. A direct application would be the attenuation of exhaust noise along a pipe (eg. fan noise reduction). An alternative use case could also be the reduction of radiated sound from wind instruments, such as a mute, without the penalty of occluding the bell of the instruments which is known to degrade the playability of the instrument.
The project will consist in the development of a COMSOL (and/or analytical) model of the plasma sound absorber ring along a duct, that will serve for geometry and control optimization. After dthis simulation step, a prototype will be constructed and tested in laboratory conditions to evaluate its applicability to various noise reduction use-cases.
- COMSOL and/or Matlab simulations
- Electroacoustic measurements
- or MA1-Audio Engineering