Loudspeaker Transducer Array Reducing Comb Filtering
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Solution Overview
Problem
Loudspeakers placed on reflective surfaces experience comb filtering effects due to phase differences between direct and reflected sounds, causing undesirable audio coloration and inconsistency in sound perception as listeners move.
Innovation Solution
The loudspeaker design includes a ring of transducers aligned in a plane, with some embodiments featuring a baseplate and angled or horn-directed sound output to minimize the distance between the transducers and the reflective surface, ensuring the direct and reflected sound paths are similar, thereby reducing comb filtering effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If transducers are placed close to the reflective surface, then the difference between direct and reflected sound paths is reduced, but the risk of resonance and unwanted reflections increases
Solution Approach 1:
The patent introduces an acoustic absorptive material as an intermediary element positioned between the transducers and the reflective surface. This mediator absorbs unwanted reflected sound energy, converting it into heat, thereby eliminating the harmful resonance and comb filtering effects without requiring the transducers to be extremely close to the reflective surface. The absorptive material allows the system to benefit from reduced path difference while avoiding the harmful reflections.
Solution Approach 2:
The patent converts the harmful reflected sound energy into a beneficial effect by using acoustic absorptive material to dissipate the reflection energy as heat. Instead of allowing the reflected sound to create comb filtering and resonance, the absorptive material transforms this harmful acoustic energy into thermal energy, effectively eliminating the problematic reflections while maintaining the proximity benefit.
2Object-generated harmful factors
If transducers are positioned far from the reflective surface, then resonance and unwanted reflections are minimized, but the difference between direct and reflected sound paths increases causing audio coloration
Solution Approach 1:
The acoustic absorptive material serves as a mediator that allows the transducers to be positioned at an optimal distance from the reflective surface. It absorbs the harmful reflected energy that would otherwise cause resonance and audio coloration, enabling the system to maintain sufficient distance to avoid unwanted reflections while preventing the path difference from causing audible comb filtering effects.
Solution Approach 2:
The acoustic absorptive material acts as a disposable energy sink that consumes the harmful reflected sound energy. This temporary absorption converts the persistent harmful reflections into a one-time energy dissipation event, effectively eliminating the comb filtering and audio coloration without requiring complex active cancellation systems.
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 design reduces comb filtering effects, providing a more consistent sound experience by minimizing the difference between direct and reflected sound paths, allowing the loudspeaker to be placed on reflective surfaces without severe audio coloration.
Implementation Method 1
A loudspeaker may be composed of multiple electro-acoustic transducers that are arranged in a speaker cabinet
Implementation Method 2
Sound emitted by the transducers may be reflected off the baseplate or other reflective surface on which the cabinet is resting
Implementation Method 3
The reflected sound may cause constructive or destructive interference with the direct sound (at the listener's ears), based on phase differences between the two sounds (caused by the delay.)
Data Source
AI summary
Loudspeakers are described that may reduce comb filtering effects perceived by a listener by either 1) moving transducers closer to a sound reflective surface (e.g., a baseplate, a tabletop or a floor) through vertical (height) or rotational adjustments of the transducers or 2) guiding sound produced by the transducers to be released into the listening area proximate to the reflective surface through the use of horns and openings that are at a prescribed distance from the reflective surface. The reduction of this distance between the reflective surface and the point at which sound emitted by the transducers is released into the listening area may lead to shorter reflected path that reduces comb filtering effects caused by reflected sounds that are delayed relative to the direct sound. Accordingly, the loudspeakers shown and described may be placed on reflective surfaces without severe audio coloration caused by reflected sounds.