A broadband active sound absorber with adjustable absorption coefficient and bandwidth

Area of Science:

• Acoustics
• Materials Science
• Signal Processing

Background:

• Controlling acoustic conditions in enclosed spaces requires effective sound absorbers.
• Existing passive and active absorbers aim for broad frequency band absorption.
• A need exists for absorbers with user-defined, tunable characteristics.

Purpose of the Study:

• To introduce a novel tunable acoustic absorber with user-defined frequency bands and absorption.
• To demonstrate adjustable broadband sound absorption capabilities.
• To enable personalized regulation of indoor acoustic environments.

Main Methods:

• Utilized an error signal synthesized via standing wave separation technique.
• Encoded target reflection coefficients to achieve arbitrary absorption coefficients (0-1).
• Experimental validation in a one-dimensional standing wave tube.

Main Results:

• Achieved near-perfect absorption (average coefficient of 0.98) from 150-1600 Hz.
• Demonstrated adjustable absorption across three octave bands, matching theoretical predictions.
• Showcased spectrally tunable broadband absorption using a shaping filter, allowing selective reflection and absorption.

Conclusions:

• The proposed active acoustic absorber offers versatile tunability for specific applications.
• The technology enables precise control over sound absorption and reflection characteristics.
• This innovation is expected to advance personalized indoor acoustic environment management.