Audio Processor Linear Nonlinear Modeling Loudspeaker Compensation
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Solution Overview
Problem
The non-linear response of loudspeakers introduces frequency content not present in the input signal, making it challenging to achieve desired sound quality in compact applications like mobile devices, where traditional methods rely on expensive materials and large size.
Innovation Solution
An audio processor is designed with a combination of linear and non-linear models to modify audio signals, using a first filter stage for a linear model and multiple second filters for inverse non-linear models applied across frequency bands, effectively compensating for the loudspeaker's non-linearities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If digital signal processing with accurate modeling is used to compensate for poor loudspeaker quality, then sound quality is improved, but device complexity increases
Solution Approach 1:
The audio processor segments the loudspeaker's frequency response into multiple frequency bands (e.g., low, mid, high ranges). Each frequency band is processed independently through separate filter stages, allowing the system to handle different non-linearities in different bands without overwhelming the processor with a single monolithic model.
Solution Approach 2:
The system dynamically adjusts filter coefficients and model parameters based on the input signal characteristics and operating conditions. By changing parameters adaptively rather than using fixed models, the processor achieves accurate compensation across varying loudspeaker conditions without requiring overly complex static models.
2Manufacturing precision
If non-linearities are modeled and compensated for, then sound quality is improved, but processing complexity increases
Solution Approach 1:
The non-linear compensation is segmented into multiple filter stages, each handling specific frequency bands with appropriate non-linear models. This divides the complex task of modeling entire-spectrum non-linearities into manageable band-specific operations.
Solution Approach 2:
The system applies non-linear modeling selectively to frequency bands where non-linearities are most problematic, rather than attempting to model all frequency ranges with equal complexity. This partial action approach focuses computational resources where they provide the most benefit.
3Manufacturing precision
If multiple filter stages are used for non-linear compensation, then sound quality is improved, but computational load increases
Solution Approach 1:
The multiple filter stages are organized to process different frequency bands in parallel or sequential manner, distributing the computational load across stages rather than concentrating it in a single processing block.
Solution Approach 2:
Each filter stage is optimized with locally-appropriate models and parameters tailored to its specific frequency band's characteristics. This local optimization reduces the need for overly complex universal models that would increase overall computational requirements.
Data Source
AI summary
Embodiments of the invention provide methods and apparatus for processing audio input signals, for example, so as to linearize the output of a given loudspeaker. An audio processor is provided, for modifying an audio signal to be provided to a loudspeaker, the audio processor comprising: a first filter stage, for applying to an audio signal a linear model describing an excursion of the loudspeaker in response to a given input signal, the linear model containing only linear terms, and for generating one or more excursion signals; a plurality of second filters for receiving the one or more excursion signals, each of the second filters configured to apply to a respective one of a plurality of frequency bands in the one or more excursion signals the inverse of a model describing an excursion of the loudspeaker in response to a given input signal; and a combiner for combining the outputs of each of the plurality of second filters. At least a first one of the plurality of second filters applies the inverse of a non-linear model describing an excursion of the loudspeaker in response to a given input signal, the non-linear model comprising one or more non-linear parameters.