Vehicle Emergency Microphone Failover with Figure-of-Eight Pattern
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Solution Overview
Problem
Emergency call systems in vehicles face challenges due to digital microphones losing directional characteristics when the infotainment system fails, leading to omnidirectional microphones that cannot distinguish between the driver and passenger, causing echo issues with the emergency call loudspeaker.
Innovation Solution
A digital microphone system with two symmetrically arranged microphone capsules connected in series with reverse polarity, generating a figure-of-eight characteristic to maintain directional orientation and reduce echo, even when the bus master fails, and an emergency call loudspeaker is positioned to minimize sound input from the microphone capsules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the infotainment system fails and the bus master becomes inactive, then the system fails over to emergency mode, but the digital microphone loses its directional characteristic and becomes omnidirectional
Solution Approach 1:
The system uses the infotainment system's own failure condition as the trigger for automatic failover to emergency mode. When the bus master detects infotainment system failure, it automatically switches the microphone configuration to emergency mode without external intervention, making the system self-sufficient during critical failures
Solution Approach 2:
The system pre-configures two microphone capsules in series with reverse polarity before the infotainment system fails. This preliminary arrangement ensures that when failover occurs, the directional characteristic is immediately restored without requiring reconfiguration or additional processing time
2Adaptability or versatility
If the microphone becomes omnidirectional, then the system can pick up sound from all directions, but the emergency call loudspeaker echoes back into the microphone
Solution Approach 1:
The system creates an asymmetric directional pattern by connecting two microphone capsules in series with reverse polarity. This configuration produces a figure-of-eight radiation pattern that is symmetric in shape but asymmetric in function, providing directional sensitivity while rejecting sounds from specific directions including the loudspeaker location
Solution Approach 2:
The system converts the harmful omnidirectional characteristic into a beneficial directional characteristic by using the reverse polarity connection. The figure-of-eight pattern created by the asymmetric connection provides both echo rejection and driver/passenger separation, turning a problem into a solution
3Device complexity
If only one digital microphone is used in emergency mode, then the system simplifies the microphone configuration, but the directional characteristic is lost
Solution Approach 1:
The system merges the functions of multiple microphone capsules into a single operational unit by connecting them in series with reverse polarity. This configuration allows two capsules to work together as one integrated microphone element, maintaining directional characteristics while simplifying the overall system architecture
Solution Approach 2:
The system changes the electrical connection parameters of the microphone capsules by switching from independent parallel connections to a series connection with reverse polarity. This parameter change transforms the combined acoustic response from omnidirectional to figure-of-eight pattern, providing directionality without increasing physical complexity
4Volume of moving object
If the emergency call loudspeaker is positioned close to the microphone, then the system achieves compact arrangement, but acoustic coupling between the loudspeaker and microphone increases
Solution Approach 1:
The system uses the asymmetric figure-of-eight radiation pattern created by the reverse polarity connection to achieve acoustic isolation. The symmetric placement of the loudspeaker relative to the microphone capsules works with the asymmetric pattern to reject sounds from the loudspeaker direction, allowing compact positioning without excessive acoustic coupling
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
Ensures effective communication with the emergency call center by maintaining directional orientation and reducing echo, allowing for better separation between the driver and passenger, even in the absence of the infotainment system's control.
Implementation Method 1
two microphone capsules (4, 6) arranged in a horizontal plane of the vehicle, in particular symmetrically with respect to the longitudinal axis of the vehicle, are connected in series with reverse polarity to one another
Data Source
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AI summary
An emergency call system of a motor vehicle comprises a digital microphone that is connected to a bus master via an automotive audio bus and is actuated by said bus master to provide a prescribed directional characteristic, wherein - the digital microphone has at least two microphone capsules, - the at least two microphone capsules are arranged symmetrically with respect to one another, - the digital microphone is arranged ahead of the location of the driver and the location of the passenger in the direction of travel, and - in the event of failure of the bus master, two microphone capsules are interconnected in series with one another with the incorrect polarity, so that a common figure-of-eight characteristic is produced, and the common signals from the digital microphone are routed out for further processing.