Audio Precompensation Controller for Loudspeaker Symmetry
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Solution Overview
Problem
Multichannel audio systems face challenges in reproducing an intended sound image due to differences in room transfer functions (RTFs) between loudspeaker pairs, leading to flawed sound image reproduction in consumer environments, as opposed to controlled studio settings where RTFs are similar.
Innovation Solution
A digital audio precompensation controller is designed to optimize filter parameters for loudspeaker systems, ensuring symmetry and similarity between RTFs of loudspeaker pairs, using a criterion function that balances target impulse responses and stability, with adjustable weights and measurement positions to improve sound quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If single-channel equalization methods are used to improve average spectral flatness, then the average spectral flatness is improved, but the variability of transfer functions within the listening region cannot be affected
Solution Approach 1:
The patent divides the equalization task into multiple independent single-channel equalization problems, one for each loudspeaker channel. Each channel is equalized separately using its own transfer function measurements, allowing individual optimization of spectral flatness for each channel while the collection of channels collectively addresses transfer function variability across the listening region.
Solution Approach 2:
The patent extends the equalization approach from single-channel to multichannel systems, where multiple loudspeakers work together to provide both individual channel equalization and collective coverage of spatial variability. The system uses measurements from multiple positions to characterize each channel's transfer function, making the equalization process adaptable to different spatial configurations.
2Reliability
If controlled studio listening environments with symmetric loudspeaker setups are assumed, then RTF similarity is achieved, but the solution does not apply to consumer home environments with flawed sound image reproduction
Solution Approach 1:
The patent changes the approach from assuming fixed symmetric RTFs in controlled environments to measuring and equalizing actual RTFs in the specific listening environment. By measuring transfer functions at multiple positions in the actual consumer environment and using these measurements to design the equalization filters, the system adapts to real-world conditions rather than relying on studio assumptions.
Solution Approach 2:
The system performs self-characterization by measuring its own transfer functions in the actual listening environment using test signals and microphones. This eliminates the need to assume symmetric RTFs based on loudspeaker placement, allowing the system to automatically adapt to the specific acoustic conditions of any environment, whether studio or consumer home.
3Reliability
If multichannel approaches are used to improve equalization performance by using all available loudspeakers jointly, then equalization performance is improved, but system complexity increases
Solution Approach 1:
The patent segments the multichannel equalization problem into independent single-channel equalization tasks. Each loudspeaker channel is equalized separately based on its own measured transfer function, avoiding the need for complex cross-channel optimization while still utilizing all available channels to address spatial variability through the collection of individually equalized channels.
Data Source
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AI summary
A basic idea is to determine an audio precompensation controller for an associated sound generating system comprising a total of N ? 2 loudspeakers, with at least one loudspeaker channel pair, each having a loudspeaker input. The audio precompensation controller has a number L ? 2 inputs for L input signal(s) and N outputs for N controller output signals, one to each loudspeaker. It is relevant to estimate (S1), for each one of at least a subset of the N loudspeaker inputs, an impulse response at each measurement position. It is also important to specify (S2), for each one of the L input signal(s), a selected one of the N loudspeakers as a primary loudspeaker and optionally a selected subset S including at least one of the N loudspeakers as support loudspeaker(s). Further it is relevant to select (S2) at least one loudspeaker pair, that is required to be symmetrical with respect to the listing position. It is relevant to specify (S3), for each primary loudspeaker, a target impulse response at each measurement position. The idea is then to determine (S4), for each one of the L input signal(s), based on the selected primary loudspeakers, the selected loudspeaker pair(s), and optionally the selected support loudspeaker(s), filter parameters of the audio precompensation controller so that a criterion function, that takes pairwise channel similarity between the selected loudspeaker pair(s) into account, is optimized under the constraint of stability of the dynamics of the audio precompensation controller.