Active Reflection Cancellation for Auditorium Reverberation Control
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Solution Overview
Problem
Large public venues like auditoriums suffer from excessive reverberation, which degrades sound quality due to echoes and reflections, and existing solutions are either impractical or ineffective in creating a consistent 'quiet zone' across the space.
Innovation Solution
A method and system that attenuate sound at or near reflective surfaces by generating a phase-opposite audio wavefront to cancel reflections, using an array of microphones and loudspeakers to reduce reverberations before they reach the audience, with adaptive algorithms to minimize error signals and ensure broad coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If loudspeakers are elevated and pointed away from the ceiling to reduce reflections, then reverberation is reduced, but the sound source becomes perceptively disjointed from the performer
Solution Approach 1:
The system segments the acoustic treatment into multiple zones: the primary sound source remains on stage for performer-audience connection, while separate cancelling loudspeakers are positioned near reflective surfaces to locally cancel reflections. This allows the main sound source to maintain its optimal positioning without causing perceptively disjointed sound, while reflections are cancelled in specific problem areas.
Solution Approach 2:
The patent introduces an intermediary system (cancelling loudspeakers and control module) between the sound source and the reflective surfaces. Instead of moving the primary sound source, the system uses intermediary devices to cancel reflections at their origin points, thereby resolving the contradiction between maintaining sound source positioning and reducing reverberation.
2Ease of operation
If loudspeakers are placed throughout the auditorium pointed at the audience to maintain sound source perception, then audience perception is improved, but reverberation and delayed reflections increase
Solution Approach 1:
The system converts the harmful effect of reflections into a beneficial outcome by using the same reflective surfaces that cause problems as mounting locations for cancelling loudspeakers. The reflections are cancelled at their origin points near the reflective surfaces, preventing them from propagating into the audience area while maintaining the perceived sound source location.
3Object-affected harmful factors
If active sound cancellation is used to create a quiet zone by attenuating reflected sounds, then reverberation is reduced, but the system requires complex tuning and expert installation
Solution Approach 1:
The system incorporates adaptive control algorithms that automatically adjust the cancellation parameters based on real-time acoustic measurements. The control module continuously monitors the acoustic environment and self-adjusts the cancelling signals, eliminating the need for manual expert tuning and making the system easier to install and maintain.
Solution Approach 2:
The patent implements feedback mechanisms where microphones monitor the actual acoustic field and the control module adjusts the cancelling loudspeaker outputs based on this feedback. This closed-loop control system automatically optimizes the cancellation performance, reducing the need for manual tuning and expert intervention during installation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces reverberations at their source, improving audio intelligibility and reducing noise transmission into surrounding environments, while being adaptable to various venue sizes and shapes.
Implementation Method 1
generating a phase-opposite cancelling audio wavefront to attenuate sound reflections
Data Source
AI summary
A method of increasing the intelligibility of an audio broadcast in an at least partially enclosed space from at least one amplified audio source. An input microphone receives an incident audio wavefront at a first position in the at least partially enclosed space. An active noise control system is employed to generate a cancelling audio wavefront having a magnitude substantially equal to the magnitude of incident audio wavefront and a phase substantially opposite to the phase of the incident audio wavefront. The cancelling audio wavefront is broadcast at a second position in the at least partially enclosed space adjacent to a reflective surface of the at least partially enclosed space so as to attenuate the incident audio wavefront substantially at or near the reflective surface in order to reduce reverberations of the incident audio wavefront. In this manner, reverberations which could reduce the intelligibility of the audio broadcast to an audience is reduced.