Active Noise Cancellation Audio Path With Near-Zero Phase Delay
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Solution Overview
Problem
Conventional active noise canceling (ANC) technologies face challenges in achieving perfect phase alignment due to phase delays in microphone and sound producing device outputs, leading to incomplete noise cancellation, especially for low-frequency noises and limited effective frequency range.
Innovation Solution
An audio apparatus and method that utilize a sound sensing device and a sound producing device with near-zero phase delay, where the sound sensing device detects ambient sound pressure and converts it into a signal with inverted polarity, and the sound producing device generates a counter sound pressure with minimal phase delay, typically less than 25 degrees, to achieve superior broadband noise isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional microphones and force-based sound producing devices are used to achieve 180-degree phase shift, then phase inversion is accomplished, but phase delay increases and low-frequency noise cancellation effectiveness deteriorates
Solution Approach 1:
The patent replaces the mechanical force-based sound producing device with an electrostatic sound producing device. This substitution eliminates the 90-degree phase delay inherent in force-based devices, reducing total phase delay from 180 degrees to approximately 90 degrees while maintaining phase inversion capability through electrical signal processing
Solution Approach 2:
The patent changes the operating parameters of the sound producing device by using electrostatic actuation instead of force-based actuation. This parameter change fundamentally alters the phase characteristics, reducing the phase delay and improving low-frequency noise cancellation effectiveness
2Reliability
If phase delay is reduced to improve low-frequency noise cancellation, then noise cancellation effectiveness improves, but the complexity of the system increases
Solution Approach 1:
The patent introduces an intermediary electrical signal processing stage between the microphone and sound producing device. This intermediary uses electrical field modulation to achieve phase inversion and delay reduction, avoiding the need for complex mechanical phase-shifting mechanisms while maintaining system reliability
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 suppresses non-stationary ambient noises and extends the upper limit of the effective frequency range for noise cancellation, providing a broader ambient noise suppression capability.
Implementation Method 1
a sound sensing device, a first amplifier... configured to convert a first signal corresponding to the ambient sound pressure into a second signal with inverted polarity
Implementation Method 2
a sound producing device... configured to produce a counter sound pressure corresponding to the second signal. Overall phase delay from the ambient sound pressure to the counter sound pressure is less than 25 degrees
Data Source
AI summary
An audio apparatus includes a sound sensing device, a first amplifier and a sound producing device. The sound sensing device configured to detect an ambient sound pressure. The first amplifier coupled to the sound sensing device is configured to convert a first signal corresponding to the ambient sound pressure into a second signal with inverted polarity of the first signal. The sound producing device is coupled to the first amplifier and configured to produce a counter sound pressure corresponding to the second signal. Overall phase delay from the ambient sound pressure to the counter sound pressure is less than 25 degrees.