Microphone Bias Control Circuit for Loud-Sound Distortion Prevention
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Solution Overview
Problem
Current sound recording devices are unable to effectively prevent sound cracks caused by microphone signals exceeding the nominal maximum output limit or due to mismatches between microphone sensitivity and bias circuit characteristics, leading to unavoidable distortion despite adjustments in amplifier gains.
Innovation Solution
A sound recording circuit that includes a microphone bias circuit, AC coupling capacitor, analog amplifier circuit, ADC, digital amplifier circuit, and signal detector, which controls the bias voltage of the microphone bias circuit to prevent clamping signals and dynamically adjusts microphone sensitivity, thereby addressing the issue of sound cracks and distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the gain of the analog amplifier and/or digital amplifier is adjusted to handle clamping phenomena, then the distortion from amplifier mismatch is reduced, but sound cracks remain when the microphone AC signal itself is a clamping signal
Solution Approach 1:
The patent applies preliminary action by detecting the signal level in advance and adjusting the bias voltage before the microphone signal is amplified. The signal detector monitors the microphone AC signal and controls the bias voltage of the microphone bias circuit proactively, preventing clamping distortion from occurring in the first place, rather than trying to correct it after amplification.
Solution Approach 2:
The patent changes the bias voltage parameter dynamically based on the detected signal level. When the signal detector detects a clamping signal or loud sound, it adjusts the bias voltage parameter of the microphone bias circuit to prevent the microphone AC signal from becoming a clamping signal, thereby resolving the contradiction between handling amplifier mismatch and preventing microphone-level clamping.
2Power
If the bias voltage is increased to handle loud sounds, then the microphone sensitivity increases, but the microphone signal may exceed the nominal maximum output limit and cause sound cracks
Solution Approach 1:
The patent implements feedback control where the signal detector continuously monitors the microphone AC signal level and provides feedback to control the bias voltage. When the signal level approaches the maximum output limit, the feedback mechanism reduces the bias voltage to prevent sound cracks, while still allowing high output power when the signal level is appropriate.
3Adaptability or versatility
If the microphone sensitivity is dynamically adjusted for different recording modes, then the adaptability to different scenarios improves, but the complexity of the control system increases
Solution Approach 1:
The patent achieves multi-functionality by using a single signal detector and bias control circuit that serves multiple purposes: it detects clamping signals, detects loud sounds, and dynamically adjusts microphone sensitivity for different recording modes. This universal control mechanism provides adaptability without requiring separate control circuits for each function, thereby limiting the increase in system complexity.
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
The circuit effectively reduces sound distortion by controlling the bias voltage and adjusting gains to prevent clamping signals, ensuring clear recordings even with loud sounds or mismatched microphone characteristics.
Implementation Method 1
The AC coupling capacitor is configured to output an analog input signal according to the microphone signal
Data Source
AI summary
Disclosed is a sound recording circuit capable of adjusting microphone sensitivity and preventing sound cracks caused by overly loud sound. The sound recording circuit includes: a microphone bias circuit configured to provide a bias voltage for a microphone circuit; an AC coupling capacitor configured to output an analog input signal according to a microphone signal of the microphone circuit; an analog amplifier circuit configured to output an analog output signal according to the analog input signal; an analog-to-digital converter configured to output a digital input signal according to the analog output signal; a digital amplifier circuit configured to output a digital output signal according to the digital input signal; and a signal detector configured to control an analog gain of the analog amplifier circuit, a digital gain of the digital amplifier circuit, and the bias voltage of the microphone bias circuit.