Sound Field Control Apparatus Using Multi-Directional Microphone Arrays
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional sound field control techniques for in-vehicle audio systems fail to effectively control sound pressure levels and air particle velocities, leading to uneven sound distribution and incorrect acoustic intensity and impedance control, resulting in undesirable sound field experiences.
Innovation Solution
A sound field control apparatus with K main microphones and K sets of sub microphones, a filtering unit, and a filter coefficient calculating unit that calculates filter coefficients to independently control sound pressure levels and air particle velocities based on detected sound pressure levels and differences between main and sub microphones, ensuring desired sound field creation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If acoustic intensity control is used to control acoustic intensities in directions excluding one direction, then sound pressure levels in that direction can be equalized, but sound pressure levels in other directions cannot be equalized and the direction of acoustic intensity flow may be opposite to desired direction
Solution Approach 1:
The patent divides the acoustic control into independent directional components by introducing multiple acoustic intensity vectors (Ix, Iy, Iz) corresponding to different spatial directions. Each direction can be controlled independently through separate filter coefficients, allowing precise control of sound pressure levels and particle velocities in each direction without interfering with other directions.
Solution Approach 2:
The patent transitions from scalar acoustic intensity control to vector-based three-dimensional acoustic intensity control. By defining acoustic intensity as a vector quantity with components in x, y, and z directions, the system can control sound field characteristics in multiple dimensions simultaneously, resolving the directional limitations of conventional single-direction control methods.
2Manufacturing precision
If acoustic impedance control is used to control acoustic impedance in one direction, then reflected sound in that direction can be canceled, but acoustic impedances in other directions cannot be controlled to desired values
Solution Approach 1:
The patent segments the acoustic impedance control into independent directional components by defining separate acoustic impedance values (Zx, Zy, Zn) for different directions. Each direction's impedance can be controlled independently through dedicated filter coefficients, enabling precise reflection cancellation in each direction without affecting control in other directions.
Solution Approach 2:
The patent extends acoustic impedance control from scalar to vector representation by introducing directional impedance components. This allows the system to control acoustic impedance characteristics in three-dimensional space, enabling independent optimization of sound field properties in each spatial direction.
3Manufacturing precision
If conventional sound field control methods are used, then sound pressure level can be controlled at a fixed point, but particle velocity cannot be controlled and the feeling of strangeness in sound direction occurs
Solution Approach 1:
The patent merges sound pressure level control and particle velocity control into a unified vector-based acoustic intensity control system. By combining these two previously separate control objectives into a single framework using acoustic intensity vectors, the system can simultaneously control both magnitude and direction of sound propagation, eliminating the unnatural sound direction perception.
Solution Approach 2:
The patent changes the fundamental control parameter from scalar sound pressure level to vector acoustic intensity, which incorporates both sound pressure and particle velocity information. This parameter transformation enables direct control of sound propagation characteristics, including directionality, thereby improving sound field realism and eliminating unnatural directional perception.
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A sound field control apparatus includes K (K ‰¥ 2) main microphones (1), K sets of sub microphones (2 -1 , 2 -2 , 2 -3 ) arranged such that X (X ‰¥ 2) sub microphones (2 -1 , 2 -2 , 2 -3 ) are placed in different axis directions about each of the main microphones (1), a filtering unit (3), and a filter coefficient calculating unit (5) configured to calculate a filter coefficient for the filtering unit (3). A filter coefficient used to control sound pressure levels and air particle velocities (v x1 , v x2 , v x3 ) of an output audio signal is calculated on the basis of a sound pressure level detected by each main microphone (1) and the difference between the sound pressure level detected by the main microphone (1) and that detected by each of the corresponding sub microphones (2 -1 , 2 -2 , 2 -3 ).