Active Noise Reduction System Virtual Microphone Positioning
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Solution Overview
Problem
Existing noise reduction headphones face discomfort and potential microphone damage due to the placement of microphones close to the user's ear, and existing systems struggle to maintain effective noise cancellation while keeping the microphone safe and comfortable.
Innovation Solution
An active noise reduction system with an earphone that includes a cup-like housing, a transmitting transducer, an error microphone within the earphone cavity, and a control unit that generates a noise-reducing signal by modeling the transfer characteristics to virtually shift the microphone position, allowing for effective noise cancellation without the need for the microphone to be close to the ear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the microphone is placed close to the user's ear for effective noise cancellation, then the noise reduction performance is improved, but the user comfort deteriorates and the microphone may be damaged
Solution Approach 1:
The patent creates a virtual microphone signal that copies the acoustic characteristics of a microphone positioned near the user's ear, while the physical microphone remains in a safe, protected position within the earphone cavity. This virtual copy allows the system to achieve noise cancellation performance equivalent to close positioning without the discomfort or damage risks to the user
Solution Approach 2:
The patent introduces signal processing as an intermediary between the physical microphone and the noise cancellation algorithm. By modeling the transfer characteristics and generating a virtual microphone signal, the system mediates between the physical constraints of microphone placement and the performance requirements of noise reduction
2Reliability
If the microphone is placed close to the user's ear for effective noise cancellation, then the noise reduction performance is improved, but the microphone protection deteriorates
Solution Approach 1:
The patent creates a virtual microphone signal that replicates the acoustic measurements that would be obtained if the microphone were positioned near the user's ear. The physical microphone remains in a protected position within the earphone cavity, eliminating exposure to sweat, moisture, and mechanical damage while maintaining noise cancellation effectiveness through the virtual signal
3Ease of operation
If signal processing is used to model transfer characteristics and create virtual microphone position, then the microphone protection and user comfort are improved, but the system complexity increases
Solution Approach 1:
The patent transforms the physical position parameter of the microphone into a virtual position through signal processing. By changing the domain from physical space to signal space, the system achieves the acoustic characteristics of close positioning without the mechanical complexity of physically relocating the microphone or its protective structures
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 solution provides effective noise reduction while maintaining the microphone's mechanical protection and user comfort by using signal processing to simulate a virtual microphone position, thus improving the overall performance and stability of the noise reduction system.
Implementation Method 1
a transmitting transducer that converts electrical signals into acoustical signals to be radiated to the user's ear
Implementation Method 2
an error microphone that converts acoustical signals into electrical signals
Implementation Method 3
a control unit that compensates for the ambient noise by generating a noise reducing electrical signal supplied to the transmitting transducer
Data Source
Figure 1~3
Figure 4
Figure 5~7
AI summary
An active noise reduction system is presented which includes an earphone (11) to be acoustically coupled to a user's ear (12) exposed to noise (3). The earphone has a cup-like housing with an aperture (15); a transmitting transducer (16) for converting electrical signals into acoustical signals to be radiated to the user's ear is arranged at the aperture of the cup-like housing (14) thereby defining an earphone cavity (17); and a receiving transducer (18) which converts acoustical signals into electrical signals and which is arranged within the earphone cavity; a first acoustical path (19) which extends from the transmitting transducer to the ear and which has a first transfer characteristic; a second acoustical path (20) which extends from the transmitting transducer to the receiving transducer and which has a second transfer characteristic; and a control unit which is electrically connected to the receiving transducer and the transmitting transducer and which compensates for the ambient noise by generating a noise reducing electrical signal supplied to the transmitting transducer. The noise reducing electrical signal is derived from the receiving-transducer signal filtered with a third transfer characteristic and the second and third transfer characteristics together model the first transfer characteristic.