In many workspaces, low-frequency noises (LFN), as experienced with industrial machinery, electric transformer and air flow machinery, are the most problematic in terms of noise abatment. Unlike mid- and high-frequency noise, LFN is less attenuated by walls and other soundproofing materials due to the long wavelength involved. In such situations, it is more efficient to design an active control system that attempts to reduce noise only on a particular region of space, which is commonly referred to as a quiet zone.

In a conventional local noise control system, a secondary source (loudspeaker) is used to cancel the sound pressure at a closely spaced error microphone. Recently, the Acoustic group at EPFL-LTS2 has developed a multichannel decentralised control system for remote quiet zone design which does not require direct monitoring of the primary field nor additional sensor in the target region. An average noise reduction of about 6 dB was measured in an idealistic free field environment.

This semester project proposes to study and improve this multichannel control system and assess its performance in a more realistic environment generated by a customizable diffuse sound field.

The proposed work will mainly consist in:

• Implementing/testing an active noise control experiment in a real room,

• Setting up a 3D audio rendering system to generate a customizable diffuse sound field,

• Defining an optimal configuration/strategy with respect to a given sound field,

• Programming the real-time controller on a LabVIEW cRIO platform.

Keywords: active noise control, 3D audio, room acoustics, loudspeaker

Profile: Electrical engineering, Micro-engineering, Mechanical engineering

Context: Theory (20%), Design (20%), Experiments (60%)

Prerequisites: Audio Engineering (MA1)