Dual-Sensitivity Microphone for High SPL Audio Capture
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Solution Overview
Problem
Mobile devices with multimedia capabilities struggle to capture high-quality audio in high sound pressure level environments due to microphone saturation and wind noise, leading to distortion and compression, which are not effectively addressed by existing microphone arrangements and digital signal processing techniques.
Innovation Solution
The use of two audio transducers with different sensitivities, where one is desensitized to prevent saturation and both output signals are combined on a single pulse density modulation stream, allowing for selective signal processing and noise reduction through high-pass filtering, enabling effective audio capture in high SPL and windy conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single microphone with high sensitivity is used, then audio quality at normal levels is improved, but saturation and distortion occur in high SPL environments
Solution Approach 1:
The system divides the audio capture function into two separate microphones with different sensitivities. The first microphone has high sensitivity for normal audio levels, while the second microphone has reduced sensitivity for high SPL environments. This segmentation allows each microphone to specialize in different acoustic conditions, resolving the contradiction between audio quality and saturation resistance.
Solution Approach 2:
The patent changes the sensitivity parameter of the second microphone by adjusting its acoustic coupling to the diaphragm. Specifically, the second microphone uses a restricted acoustic path or acoustic impedance matching network that reduces its sensitivity compared to the first microphone. This parameter change enables the second microphone to handle high SPL signals without saturation.
2Reliability
If multiple microphones are used to capture high SPL signals, then saturation is reduced, but device complexity increases
Solution Approach 1:
The patent merges the outputs of two microphones with different sensitivities into a single audio output stream. A selector circuit or digital signal processing module combines the signals from both microphones, automatically choosing the appropriate signal based on the acoustic environment. This merging approach maintains saturation resistance while managing device complexity through integrated signal processing.
Solution Approach 2:
The multi-microphone system is designed to serve multiple functions: the first microphone handles normal audio levels with high fidelity, while the second microphone handles high SPL conditions. The system universally captures a wide range of acoustic conditions by having each microphone optimized for different operational ranges, reducing the need for external audio processing equipment.
3Adaptability or versatility
If wind noise is captured by the microphone, then audio recording in outdoor environments is possible, but intelligibility is reduced due to unwanted noise
Solution Approach 1:
The system extracts and removes wind noise from the audio signal through digital signal processing. The two-microphone array enables noise cancellation techniques where wind noise captured by one microphone is identified and subtracted from the combined signal. This extraction process maintains outdoor recording capability while improving audio intelligibility by removing the harmful wind noise component.
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 allows for clear audio recording in high SPL environments without saturation and reduces wind noise, improving the overall audio quality by selecting the least distorted signal and using high-pass filtering to suppress unwanted noise.
Implementation Method 1
Each of the plurality of membranes 120 forms a variable capacitance with the base 130. Thus, each membrane 120 effectively forms a generally independent, separate microphone with the base 130.
Data Source
AI summary
Disclosed herein are apparatus, method, and computer program product whereby a device receives an acoustic signal. In response to the received acoustic signal, the device outputs electrical signals from a first input audio transducer and a second input audio transducer. The second input audio transducer is less sensitive than the first input audio transducer.