Microphone Feedback Circuit for Audio Sensitivity Without Distortion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing microphones face challenges in increasing audio band sensitivity without boosting ultrasonic sensitivity, leading to unwanted audible distortion due to mechanical resonances.
Innovation Solution
A microphone circuit with a unity gain amplifier and a positive feedback network with fractional gain less than unity, coupled with a low pass filter, is used to boost audio band sensitivity while attenuating ultrasonic frequencies, avoiding the need for high-gain amplifiers and associated noise or current consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If typical approaches are used to boost microphone sensitivity in the audio band, then sensitivity increases, but ultrasonic sensitivity is also boosted causing increased unwanted audible distortion
Solution Approach 1:
The patent applies local quality by making different frequency bands have different gain characteristics. The feedback network provides positive feedback specifically tailored to audio frequencies while excluding ultrasonic frequencies through the low-pass filter, thereby locally optimizing sensitivity enhancement only where needed without amplifying harmful ultrasonic peaks
Solution Approach 2:
The patent implements feedback by introducing a positive feedback network that feeds a portion of the amplified audio signal back to the microphone element. This feedback mechanism, combined with the low-pass filter, creates a frequency-selective system that enhances audio band sensitivity through constructive feedback while preventing ultrasonic feedback that would cause distortion
2Measurement precision
If high-gain amplifiers are used to increase sensitivity, then sensitivity boosts, but noise and current consumption increase
Solution Approach 1:
The patent applies partial action by using a unity gain amplifier (gain = 1) rather than a high-gain amplifier, and instead achieving sensitivity enhancement through controlled positive feedback at audio frequencies only. This partial approach avoids the excessive noise and power consumption associated with high-gain amplifiers while still achieving the desired sensitivity improvement in the relevant audio band
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 approach effectively increases audio band sensitivity by 6 dB without boosting ultrasonic sensitivity, reducing audible distortion and maintaining a low noise and power consumption profile.
Implementation Method 1
producing a filtered microphone output signal by filtering, using a low pass filter, the amplified microphone signal
Implementation Method 2
feeding back the filtered microphone output signal to the electro acoustic sensor using a positive feedback network
Data Source
AI summary
A microphone circuit having an amplifier with an input operably coupled to a microphone motor also includes a low pass filter operably coupled to the output of the amplifier and a positive feedback network that operably couples to an output of the low-pass filter and to the amplifier input. For many useful application settings the aforementioned amplifier has unity gain while the positive feedback network has a fractional gain less than unity.