Digitally Adjustable Amplifier Gain for Active Noise Control Headphone Calibration
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Solution Overview
Problem
Active noise control headphones require manual calibration of microphone gains, which increases manufacturing time and costs, and can be less accurate due to mechanical adjustments and alterations in acoustic behavior.
Innovation Solution
An active noise control arrangement with a digitally adjustable amplifier and filter, allowing for electronic gain adjustment via a digital interface, eliminating the need for manual trimmer potentiometers and improving calibration accuracy and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If manual calibration with trimmer potentiometers is used, then gain adjustment is possible, but manufacturing time increases and costs increase
Solution Approach 1:
The patent replaces manual mechanical adjustment of trimmer potentiometers with automated electronic gain control. The system uses a digital signal processor to automatically adjust amplifier gains through electronic means, eliminating the need for manual mechanical calibration while improving both speed and precision.
Solution Approach 2:
The calibration system performs self-calibration automatically without requiring manual intervention. The digital signal processor automatically measures microphone responses and adjusts amplifier gains based on measured data, enabling the system to calibrate itself during manufacturing without operator involvement.
2Manufacturing precision
If manual calibration is performed, then gain adjustment can be made, but calibration time per unit increases
Solution Approach 1:
The system performs preliminary measurements of microphone characteristics during assembly, storing this data for use in the calibration process. By having measurement data ready before calibration begins, the system can quickly compute and apply gain adjustments without time-consuming manual measurements.
Solution Approach 2:
The calibration system uses feedback from actual microphone measurements to automatically adjust amplifier gains. The digital signal processor continuously monitors the response and makes real-time adjustments, ensuring precise calibration while minimizing the time required through iterative optimization.
3Ease of operation
If ear cup openings are made for trimmer access, then manual adjustment is possible, but acoustic behavior is altered reducing accuracy
Solution Approach 1:
The patent eliminates the need for mechanical trimmer potentiometers that require physical access through ear cup openings. Instead, it uses fully electronic gain control implemented through digital signal processing, allowing calibration to be performed through existing acoustic paths without modifying the ear cup structure.
Solution Approach 2:
The digital signal processor serves multiple functions: it processes audio signals during normal operation and simultaneously performs calibration functions by measuring microphone responses and adjusting gains. This multi-functionality eliminates the need for separate mechanical adjustment mechanisms and openings.
Data Source
AI summary
An active noise control arrangement has a signal input (SI), a microphone input (MI), a signal output (SO) and a digital interface (DI). A signal processing block (SP) coupled to the microphone input (MI) by means of an amplifier (MA) has a digitally adjustable gain and comprises combining means (CM) and a filter (TP). The signal processing block (SP) is configured to generate an output signal at the signal output (SO) as a function of an input signal at the signal input (SI) and an amplified microphone signal. A control block (CB) is coupled to the digital interface (DI) and configured to adjust the gain of the amplifier (MA).