Loudspeaker Equalization Using Room Gain and Multi-Point Sound Fields
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Solution Overview
Problem
Existing methods for controlling loudspeakers in small or closed enclosures, such as vehicle cabins, fail to effectively adjust the sound field to optimize acoustic power output, room gain, and listener position interface, leading to suboptimal sound distribution and reception.
Innovation Solution
A method and system that determine acoustic power output, room gain, and listener position interface by measuring sound pressures at multiple positions, calculating radiation resistance, and applying filter characteristics to adjust the sound field, incorporating real-time adaptation to changing conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If single point room equalization is used by measuring sound pressure in one point, then the control system is simple, but the sound field optimization is insufficient
Solution Approach 1:
The patent divides the enclosure space into multiple measurement positions and divides the frequency range into multiple bands. Instead of using a single measurement point, the system measures sound pressure at multiple positions (at least two) distributed throughout the enclosure, and applies separate filter characteristics for different frequency bands. This segmentation approach comprehensively characterizes the sound field distribution while maintaining manageable system complexity.
Solution Approach 2:
The patent transitions from single-point measurement to multi-point spatial measurement, adding the spatial dimension to the measurement process. By measuring at multiple positions throughout the enclosure and combining these measurements with frequency band analysis, the system creates a comprehensive multi-dimensional characterization of the sound field, enabling much more accurate optimization.
2Power
If acoustic power output is optimized without considering room gain, then speaker output is maximized, but the overall sound field quality deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the system measures the actual sound pressure at multiple positions in the enclosure, calculates the room gain based on these measurements, and uses this feedback information to determine appropriate filter characteristics. The filter is designed to compensate for the measured room gain, ensuring that the optimized acoustic power output actually produces high-quality sound field distribution throughout the enclosure.
Solution Approach 2:
The patent changes the approach from directly maximizing speaker power output to optimizing the filter characteristics based on measured acoustic parameters. By measuring room gain and using this information to adjust the filter parameters, the system transforms the power optimization problem into a parameter optimization problem, where the filter characteristics are specifically tailored to the measured acoustic environment.
3Ease of operation
If filter characteristics are determined without real-time adaptation, then the system is simpler to operate, but the sound quality deteriorates under changing conditions
Solution Approach 1:
The patent implements dynamic adaptation by allowing the system to update filter characteristics in real-time based on changing conditions. The system can re-measure the sound field and recalculate optimal filter parameters when environmental conditions change (such as doors opening/closing, passengers entering/exiting). This dynamic capability maintains sound quality under varying conditions while the initial setup remains straightforward.
Solution Approach 2:
The patent performs preliminary measurements and filter design during system setup or calibration phases, storing these characteristics for later use. This preliminary action simplifies everyday operation since the system has pre-determined optimal settings. When needed, the system can perform additional measurements and updates without requiring complex real-time adjustments during normal operation.
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 solution enables precise control of sound distribution, optimizing acoustic power output and listener reception across the full audible frequency range, with real-time adjustments to ensure optimal sound quality despite changes in the environment or loudspeaker properties.
Implementation Method 1
measuring sound pressures at a plurality of positions while emitting an acoustic signal by means of the sound source
Implementation Method 2
based on the measured sound pressures at the two positions calculating the radiation resistance in the near field of the sound source
Data Source
AI summary
The present invention relates to methods and systems for determining an equalization filter for one or more loudspeakers provided in an enclosure, such as a listening room or an automobile cabin. A method for determining an equalization filter for one or more loudspeakers provided in an enclosure comprises the steps of providing the one or more loudspeakers with an audio input signal whereby a sound field is generated in the enclosure; determining an acoustic contribution or room gain of the enclosure to the generated sound field; forming a speaker equalization filter as the square root of the ratio between a target acoustic power output and the actual acoustic power output from the loudspeaker driver(s), which actual acoustic power output is calculated as the square of the power averaged sound pressure divided by the room gain; and determining the equalization filter as the speaker equalization filter.