Variable Acoustics Loudspeaker Beamforming for Directivity Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional loudspeakers exhibit frequency-dependent directivity patterns that are difficult to control, often leading to unwanted sound energy dispersion and requiring acoustic treatment to ensure precise stereo imaging.
Innovation Solution
A variable acoustics loudspeaker system with cylindrical arrays of drivers, utilizing digital signal processing and beamforming filters to steer sound beams in desired directions, achieving precise control over directivity and reducing unwanted reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional loudspeakers with single drivers per frequency band are used, then the structure is simple, but the directivity pattern is difficult to control and sound energy disperses in all directions
Solution Approach 1:
The loudspeaker is divided into multiple frequency bands (e.g., 5 bands: 20-80Hz, 80-250Hz, 250-1kHz, 1-4kHz, 4-20kHz), with each band having dedicated drivers. This segmentation allows independent control of directivity for each frequency range, solving the problem of uncontrollable sound dispersion while maintaining manageable structural complexity.
Solution Approach 2:
The system employs dynamic directivity control through adjustable parameters including vertical tilt angle (±15°), horizontal pan angle (±45°), and selectable beam widths (narrow, medium, wide). This dynamic adjustment capability enables precise control over sound projection direction and coverage area, transforming the static directivity pattern into an adaptable system that responds to different listening environments.
2Measurement precision
If acoustic treatment is added to dampen unwanted reflections, then sound imaging precision is improved, but device complexity and room requirements increase
Solution Approach 1:
The system extracts and directs sound energy into controlled beams with specific directional patterns, concentrating acoustic output toward the intended listening area. By taking sound energy away from unwanted reflection paths and channeling it through directed beams, the system achieves precise stereo imaging without requiring external acoustic treatment to dampen reflections.
Solution Approach 2:
Instead of treating reflections as harmful elements to be dampened, the system converts the challenge of room acoustics into a benefit by using electronic directivity control to override room characteristics. The adjustable beam patterns allow the loudspeaker to compensate for room acoustics actively, transforming the need for passive acoustic treatment into an active electronic solution.
3Shape
If vertical lobing occurs due to non-coincident drivers, then the directivity pattern becomes frequency-dependent, but control over sound distribution is lost
Solution Approach 1:
Each frequency band is assigned specific drivers positioned at optimized locations, with local directivity control parameters (vertical tilt, horizontal pan) adjusted according to the characteristics of that frequency range. This local quality approach ensures that each band contributes appropriately to the overall directivity pattern, maintaining control over sound distribution despite the frequency-dependent nature of driver radiation.
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 adjustable listening areas with focused sweet spots, suppresses rear energy by 20 dB, and enables full-sphere sound field control without room treatment, offering improved sound imaging and reduced dispersion.
Implementation Method 1
A digital signal processor is programmed to generate a first plurality of output channels from an input channel for the first range of frequencies, apply the first plurality of output channels to the first array of speaker elements using a first rotation matrix to rotate a first beam of audio content to a target angle about the axis
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A first array of M speaker elements is disposed in a cylindrical configuration about an axis and configured to play back audio at a first range of frequencies. A second array of N speaker elements is disposed in a cylindrical configuration about the axis and configured to play back audio at a second range of frequencies. A digital signal processor generates a first plurality of output channels from an input channel for the first range of frequencies, apply the first plurality of output channels to the first array of speaker elements using a first rotation matrix to generate a first beam of audio content at a target angle about the axis, generate a second plurality of output channels from the input channel for the second range of frequencies, and apply the second plurality of output channels to the second array of speaker elements using a second rotation matrix to generate a second beam of audio content at the target angle.