Room Echo Estimation Using Image Sources and Compact Microphone Arrays
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Solution Overview
Problem
Existing methods for determining the location of room walls using microphone arrays in loudspeaker systems are limited by strict requirements on excitation signals and empirical modeling, leading to information loss and restricted applicability to specific microphone types and wall properties.
Innovation Solution
A method that includes the excitation signal in the signal model, eliminates the need for pre-processing deconvolution, and uses a multichannel filter to model relative microphone delays analytically, allowing for robust estimation of room geometry with a compact microphone array, capable of detecting both vertical and non-vertical surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If deconvolution of excitation signal is performed to obtain channel estimate, then room impulse response can be estimated, but information loss occurs and strict requirements on excitation signals are imposed
Solution Approach 1:
The patent applies preliminary action by incorporating the excitation signal characteristics into the signal model before processing. The known excitation signal is integrated into the multichannel filterbank model, allowing the system to directly estimate room impulse responses without requiring separate deconvolution operations that cause information loss.
Solution Approach 2:
The patent uses a multichannel filterbank as an intermediary structure that models the relationship between the excitation signal and microphone recordings. This filterbank acts as a mediator that incorporates excitation signal characteristics while avoiding the information loss associated with traditional deconvolution approaches.
2Measurement precision
If empirical modeling with pre-stored dataset is used to identify echoes, then wall location can be determined, but the system is restricted to specific microphone types and wall properties
Solution Approach 1:
The patent achieves universality by creating a signal model that is independent of specific microphone types and wall properties. The multichannel filterbank approach with image sources provides a general framework that can adapt to different microphone arrays and various wall characteristics without requiring empirical datasets specific to each configuration.
Solution Approach 2:
The patent applies parameter changes by using a flexible signal model where parameters such as microphone positions, loudspeaker characteristics, and wall locations can be varied without requiring re-calibration with empirical datasets. The model adapts to different configurations by changing its parameters rather than requiring different empirical models.
3Device complexity
If compact microphone array is used, then device complexity is reduced, but measurement precision for determining wall locations becomes more challenging
Solution Approach 1:
The patent applies preliminary action by incorporating all available information about the compact microphone array geometry and characteristics into the signal model before processing. The multichannel filterbank is designed with prior knowledge of the compact array configuration, enabling accurate wall location estimation despite the reduced array size.
Solution Approach 2:
The patent substitutes the mechanical approach of using large microphone arrays with a signal processing approach using multichannel filterbanks. Instead of relying on physical array size for precision, the system uses sophisticated signal modeling that extracts maximum information from the compact array configuration.
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
This approach provides a more versatile and robust method for estimating room geometry, reducing reliance on specific excitation signals and microphone types, and enabling accurate detection of room surfaces without information loss.
Implementation Method 1
when a loudspeaker emits a sound signal into the room, it will be reflected (echoed) by the walls. The microphones will receive these echoes in the form of delayed versions of the transmitted signal
Data Source
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AI summary
A method for estimating an acoustic influence of walls of a room, comprising emitting a known excitation sound signal, receiving a set of measurement signals, each measurement signal being received by one microphone in a microphone array and each measurement signal including a set of echoes caused by reflections by the walls, solving a linear system of equations to identify locations of image source and estimating the acoustic influence based these image sources. The signal model includes a convolution of: - the excitation signal, - a multichannel filter (M) representing the relative delays of the microphones in the microphone array, the relative delays determined based on a known geometry of the microphone array, and - a directivity model v(n, p) of the driver(s) in the form of an anechoic farfield impulse response as a function of transmit angle.