Virtual Microphone Noise Estimation for Engine Order Cancellation
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Solution Overview
Problem
Traditional Engine Order Cancellation (EOC) systems in vehicles face performance issues due to sub-optimal microphone placement and frequency-dependent correlation between error microphones and occupant ear positions, leading to ineffective noise cancellation at the occupant's ear location.
Innovation Solution
A method for estimating noise at a virtual microphone location using a virtual path filter and adaptive weighting based on current vehicle conditions, such as engine load and speed, to generate an estimated noise signal that accurately represents the noise at the occupant's ear position, allowing for improved noise cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional error microphones are used for noise cancellation, then the system structure is simple, but the noise cancellation accuracy at occupant ear position deteriorates due to sub-optimal microphone placement and frequency-dependent correlation
Solution Approach 1:
The patent creates a virtual microphone signal that copies the acoustic characteristics of the occupant ear position by processing signals from existing error microphones through virtual path filters. This virtual copy allows accurate noise estimation at the ear position without physically placing microphones there, thereby improving measurement precision while avoiding additional hardware complexity
Solution Approach 2:
The patent introduces virtual path filters as intermediary components that mediate between the error microphone signals and the virtual microphone output. These filters act as mathematical intermediaries that transform the error microphone signals into accurate representations of the ear position acoustic environment, resolving the contradiction between simple structure and accurate measurement
2Reliability
If the number of error microphones is increased to improve noise cancellation, then the noise cancellation performance improves, but the device complexity and cost increase
Solution Approach 1:
The patent creates accurate virtual representations of multiple ear positions using signals from a limited number of physical error microphones. By generating virtual microphone signals through mathematical processing and virtual path filters, the system achieves reliable noise cancellation performance without increasing the physical microphone count, thus improving reliability while reducing device complexity
Solution Approach 2:
The patent makes the existing error microphones serve multiple functions: they simultaneously provide feedback for adaptive filter adjustment and serve as sources for generating virtual microphone signals at occupant ear positions. This multi-functionality allows the system to achieve improved noise cancellation performance without adding dedicated microphones for each function, reducing overall device complexity
3Measurement precision
If static weighting is used for error microphone signals, then the system is simple to implement, but the noise estimation accuracy deteriorates in dynamic vehicle conditions
Solution Approach 1:
The patent implements dynamic weighting coefficients that automatically adjust based on current vehicle conditions such as engine speed, load, and operating state. This dynamic adaptation allows the system to maintain high noise estimation accuracy across varying conditions by optimizing the contribution of each error microphone signal in real-time, resolving the contradiction between measurement precision and processing complexity through adaptive algorithms
Solution Approach 2:
The patent changes the weighting parameters from static fixed values to dynamic variables that depend on vehicle operating conditions. By making the weighting coefficients dependent on parameters like engine RPM and load, the system achieves accurate noise estimation in dynamic conditions while the underlying processing structure remains manageable through parameter-based adaptation
Data Source
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AI summary
A system and method for accurately estimating engine noise at a virtual microphone location, such as an occupant's ear position, in an acoustic space in order to enhance performance of an Engine Order Cancellation (EOC) system is provided. A set of weights and transfer functions that are dependent on various vehicle parameters, such as frequency, load, and speed, may be employed to estimate noise at a position where there are no physical microphones present. The accurate estimation of engine noise at virtual location, such as an occupant's ear position, may be achieved using a frequency dependent weighted sum of filtered and unfiltered error signals measured at microphones mounted at various locations inside an acoustic space, such as a vehicle cabin, which may not be located near virtual location.