Loudspeaker Array Tube Baffle Spacing for Uniform Sound

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Solution Overview

Problem

Existing loudspeaker arrays face challenges in achieving uniform sound propagation in all directions due to interference between speakers, leading to cancellation effects and reduced intelligibility, especially in public address systems where directional sound distribution is critical.

Innovation Solution

A loudspeaker system comprising multiple linear arrays arranged in elongated rectangular baffles forming a multi-sided tube, with speaker transducers spaced no further than one quarter wavelength of a selected minimum frequency, allowing for dynamic phase adjustment and steering of the sound field to achieve uniform sound distribution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If rectangular speakers are arranged in a circumferentially spaced relationship in a common horizontal plane, then the warning system can cover all directions, but interference between adjacent speakers causes cancellation effects and non-uniform sound distribution in certain directions

Engineering Contradiction:

Improveomni-directional sound coverageVSAvoiduniformity of sound propagation

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The system divides the loudspeaker array into multiple linear arrays (at least three) arranged in elongated rectangular baffles forming a multi-sided tube structure. Each linear array contains speaker transducers spaced at specific intervals (no further than one quarter wavelength of a selected minimum frequency). This segmentation into structured linear arrays reduces interference and cancellation effects while maintaining omnidirectional coverage.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies different spacing criteria to different groups of speakers based on their positions and functions. Speaker transducers within each linear array are spaced no further than one quarter wavelength of a selected minimum frequency, while the linear arrays themselves are arranged in a multi-sided tube configuration. This local optimization of spacing ensures uniform sound propagation while maintaining directional coverage.

Inventive Principle:

Principle #3Local quality

2Reliability

If adjacent loudspeakers are driven at different frequencies to eliminate cancellation effects, then uniform sound distribution improves, but speech intelligibility deteriorates due to pitch changes depending on direction

Engineering Contradiction:

Improveuniformity of sound distributionVSAvoidspeech intelligibility

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The system maintains all speaker transducers operating at the same frequency to preserve speech intelligibility and consistent pitch perception from all directions. Instead of using frequency differentiation, the patent achieves uniform sound distribution by carefully controlling the spatial arrangement and spacing of speakers (no further than one quarter wavelength of a selected minimum frequency) and utilizing phase adjustment capabilities.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If speaker transducers are spaced closer than one quarter wavelength of a selected minimum frequency, then cancellation effects are reduced, but the system complexity and manufacturing difficulty increase

Engineering Contradiction:

Improvereduction of cancellation effectsVSAvoidspeaker spacing requirements

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent establishes a specific spacing parameter for speaker transducers (no further than one quarter wavelength of a selected minimum frequency) that optimizes the balance between reducing cancellation effects and maintaining practical system complexity. This parameter-based approach provides clear design guidelines that simplify manufacturing while achieving the desired acoustic performance.

Inventive Principle:

Principle #35Parameter changes

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

The system provides nearly uniform signal intensity in all directions, maintaining high speech intelligibility and effective sound coverage across a broad frequency range, with the ability to tilt and adjust lobes for optimal audience coverage.

Implementation Method 1

The speaker transducers of each rank are spaced no further from one another than one quarter wavelength of a selected minimum frequency

Methodology Applied

Scientific EffectSound wave propagation: Sound

Implementation Method 2

Iacono et al., in U.S. Pat. No. 4,633,229, attributed the problem on uneven distribution of sound from such a system to interference between adjacent speakers resulting in cancellation effects in certain directions

Methodology Applied

Scientific EffectAcoustic interference: Interference

Data Source

PatentUS8311261B2Acoustic transducer array

Publication Date: 2012.11.13 GRABER CURTIS E

AI summary

A loudspeaker system comprises a plurality of speaker transducer units divided among and arrayed in at least three linear arrays. The linear arrays are disposed in a like plurality of elongated rectangular baffles. The elongated rectangular baffles are disposed in side by side relationship along the respective elongated sides of the baffles in the form of a tube. The speaker transducer units are aligned in a plurality of ranks. The ends of the tube are closed with the result that one side of speaker transducers radiates into the interior of the enclosure and the other side radiates into the environment. The speaker transducers of each rank are spaced no further from one another than one quarter wavelength at a selected frequency.