Dual-Microphone Stethoscope Noise Cancellation by Signal Correlation
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Solution Overview
Problem
Traditional stethoscopes capture both desired and ambient sounds, leading to interference and distortion when ambient sounds are loud, necessitating a solution to enhance sound clarity.
Innovation Solution
An active noise cancellation stethoscope with a main and sub microphone system, a sound processing device, and a control unit that automatically activates noise cancellation based on correlation coefficients to minimize ambient noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If active noise cancellation is continuously performed, then ambient noise is reduced, but power consumption increases
Solution Approach 1:
The patent implements dynamic control of the active noise cancellation function by continuously calculating correlation coefficients between microphone signals and automatically activating or deactivating the noise canceller based on whether the correlation exceeds a threshold, allowing the system to adapt its operation to current acoustic conditions rather than running continuously
Solution Approach 2:
The system performs periodic correlation calculations at specific intervals to determine whether noise cancellation should be active, using time-windowed analysis of the audio signals to make periodic decisions about activating or deactivating the noise canceller, thereby reducing overall power consumption while maintaining effectiveness when needed
2Measurement precision
If active noise cancellation is always activated, then sound clarity is improved, but unnecessary power is consumed when ambient noise is low
Solution Approach 1:
The system uses feedback control by continuously monitoring the correlation between signals from different microphones and using this information to automatically adjust the state of the active noise canceller, ensuring the function is only active when acoustic conditions indicate it would be beneficial for sound clarity
Solution Approach 2:
The stethoscope automatically determines when noise cancellation is needed through self-monitoring of its own microphone inputs, calculating correlation coefficients and making autonomous decisions about activating or deactivating the noise canceller without requiring external control or user input
3Measurement precision
If correlation calculation is performed continuously, then noise cancellation accuracy is improved, but processing time and power increase
Solution Approach 1:
The system performs correlation calculations periodically at defined intervals rather than continuously, using time-windowed signal analysis to determine noise cancellation needs at specific moments, thereby reducing computational load and processing time while maintaining adequate accuracy for clinical use
Data Source
AI summary
An active noise cancellation stethoscope including a sound receiving device, a sound processing device, and a control unit is provided. The sound receiving device includes a main microphone and a sub microphone. The main microphone is configured to receive and output a first sound signal and the sub microphone is configured to receive and output a second sound signal. The sound processing device is coupled to the sound receiving device to receive the first and second sound signals, and is configured to convert the first and second sound signals into third and fourth sound signals in digital mode respectively. The control unit is coupled to the sound processing device, and is configured to calculate the correlation between the third and fourth sound signals in order to determine whether to perform an active noise cancellation operation.