Virtual Microphone ANC for High-Frequency Airborne Vehicle Noise
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Solution Overview
Problem
Existing noise cancellation systems struggle to effectively cancel high-frequency broadband airborne noise in vehicles, as conventional sensors like accelerometers primarily capture structure-borne noise, and passive solutions like laminated glass provide benefits only above 1.5 kHz, leaving a significant gap in the 300 Hz to 1000 Hz frequency band.
Innovation Solution
Incorporating additional sensors such as MEMS microphones and hot-wire sensors on the vehicle exterior, along with accelerometers, to capture airborne noise, and utilizing a virtual microphone algorithm to estimate noise signals at virtual locations, allowing for improved noise cancellation in the 300 Hz to 1000 Hz frequency band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional sensors like accelerometers are used for noise cancellation, then structure-borne noise can be captured, but high-frequency airborne noise in the 300 Hz to 1000 Hz band cannot be effectively captured
Solution Approach 1:
The patent combines multiple sensor types (accelerometers for structure-borne noise, MEMS microphones for airborne noise) into a hybrid sensing system. This merging allows the system to capture both structure-borne and airborne noise across a broader frequency spectrum, particularly addressing the gap in the 300 Hz to 1000 Hz band where conventional single-sensor systems fail.
Solution Approach 2:
The sensing system is designed to perform multiple functions: accelerometers detect structure-borne vibrations while MEMS microphones capture airborne sound waves. This multi-functional approach enables a single system to handle diverse noise types and frequency ranges, improving overall measurement precision without requiring separate specialized systems.
2Object-affected harmful factors
If passive solutions like laminated glass are used, then noise above 1.5 kHz is reduced, but noise in the 300 Hz to 1000 Hz frequency band remains uncanceled
Solution Approach 1:
The patent changes the working frequency parameters of the ANC system to at least 2 kHz, enabling effective cancellation in the 300 Hz to 1000 Hz band. This parameter adjustment, combined with specialized sensors positioned to capture mid-frequency airborne noise, extends the system's adaptability beyond traditional high-frequency-only solutions.
3Measurement precision
If MEMS microphone is placed inside outside mirror to capture wind noise, then airborne noise capture is improved, but self-noise from the microphone increases
Solution Approach 1:
The outside mirror housing acts as an intermediary structure that directs airflow away from the MEMS microphone while still allowing it to capture relevant airborne noise. This intermediary placement reduces turbulence-induced self-noise from the microphone itself, improving the signal-to-noise ratio for captured wind and airborne noise.
4Reliability
If multiple sensors are added to capture high-frequency airborne noise, then noise cancellation performance is enhanced, but device complexity increases
Solution Approach 1:
The patent segments the noise sensing function into distinct components: accelerometers for structure-borne noise, MEMS microphones for airborne noise, and hot-wire sensors for velocity measurement. This segmentation allows each sensor type to be optimized for its specific function while working together in an integrated system, managing complexity through functional separation.
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
Enhances noise cancellation performance by capturing and processing high-frequency airborne noise, effectively reducing interior noise levels in vehicles, particularly at speeds where these frequencies dominate.
Implementation Method 1
a MEMS microphone located inside an outside mirror of a vehicle, to allow the MEMS microphone to capture wind noise of the vehicle, and coupled to outside air per a submillimeter hole in the outside mirror to minimize self-noise from the MEMS microphone
Implementation Method 2
a hot-wire sensor configured to provide a direct measurement of sound velocity
Implementation Method 3
a hot-wire sensor configured to provide a direct measurement of sound velocity and located at an outside mirror of the vehicle or a front bumper of the vehicle, to capture structure-borne noise as well as airborne noise
Implementation Method 4
an accelerometer located in a windshield, a sunroof, a rear windshield, or interior body panels of the vehicle
Implementation Method 5
The destructively-interfering sound waves may be produced through a loudspeaker to combine with the undesired sound waves in an attempt to cancel the undesired noise
Implementation Method 6
Active noise cancellation (ANC) may be used to generate sound waves or anti-noise that destructively interferes with undesired sound waves
Data Source
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AI summary
Noise signals are captured from one or more physical error microphones located at first locations within the vehicle. High-frequency noise signals are captured from a feedforward system sensor. A virtual microphone algorithm is utilized to estimate noise signals at a virtual location based on the noise signals, the estimation utilizing a transfer function that estimates a signal that would have been received by the one or more physical error microphones at the virtual location. The virtual microphone algorithm is utilized to estimate noise signals at the virtual location based on the high-frequency noise signal. A noise-cancelling signal is provided to cancel noise at the virtual location, the noise-cancelling signal accounting for the noise captured by both the feedforward system sensor and the one or more physical error microphones, the ANC system utilizing a working frequency for the ANC of at least 2 kHz.