Active room compensation for sound reinforcement using sound field separation techniques.

Area of Science:

• Acoustics
• Signal Processing
• Sound Engineering

Background:

• Controlling low-frequency sound fields in enclosed spaces is challenging due to long wavelengths and reverberation.
• Existing methods often require complex setups or are limited to specific room geometries and source positions.
• Active sound absorption at boundaries offers a potential solution for mitigating unwanted reflections and resonances.

Purpose of the Study:

• To propose and validate an indoor control method for actively absorbing sound incident on a reflecting boundary at low frequencies.
• To investigate and compare three different sound field separation techniques for modeling reflections.
• To demonstrate the effectiveness of the proposed method in reducing room resonances and enhancing low-frequency responses.

Main Methods:

• A microphone array near secondary sources separates the sound field into incident and reflected components.
• Optimal signals are generated for the secondary sources to minimize the reflected sound components (active absorption).
• Three sound field separation techniques are explored: plane wave decomposition, equivalent sources, and Spatial Fourier transform.

Main Results:

• The proposed control method successfully reduces resonances throughout the room, even with localized source and microphone placement.
• Simulations and experiments show comparable performance across the three investigated sound field separation techniques.
• The method enhances low-frequency responses by actively minimizing reflections from a boundary.

Conclusions:

• The active absorption method provides an effective means of controlling low-frequency sound fields indoors.
• The technique is versatile, applicable to arbitrary room geometries and primary source positions, unlike plane wave methods.
• This approach offers a promising solution for improving acoustic conditions in various environments.