Dual-Driver Loudspeaker Active Noise Cancellation
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Solution Overview
Problem
Active-noise cancellation (ANC) systems using balanced-armature drivers often fail to adequately cancel noise due to high latency and inadequate cancellation of high-frequency noise, making them ineffective in ambient noise environments.
Innovation Solution
A multi-driver system with an error microphone receiving audio from both low-frequency and high-frequency drivers, utilizing an adaptive controller to configure a filter that minimizes the error between noise and anti-noise, generating anti-noise data by applying playback audio to the estimated secondary path, and modifying it using a feedback controller to cancel noise effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If balanced-armature drivers are used for ANC, then device size can be reduced, but noise cancellation effectiveness deteriorates due to high latency and inadequate high-frequency cancellation
Solution Approach 1:
The patent divides the audio output into multiple frequency bands using separate drivers: a balanced-armature driver for high frequencies and a dynamic driver for low frequencies. This segmentation allows each driver to specialize in its frequency range, enabling the balanced-armature driver to effectively cancel high-frequency noise without being constrained by its bandwidth limitations when operating alone.
Solution Approach 2:
The patent combines multiple driver types (balanced-armature and dynamic drivers) into a unified ANC system that leverages the complementary strengths of each driver type. The system merges their outputs through a crossover network, creating a composite audio signal that achieves both low latency and effective high-frequency noise cancellation.
2Device complexity
If bandwidth-limited drivers are used, then device complexity can be reduced, but noise cancellation performance deteriorates due to inadequate high-frequency response
Solution Approach 1:
The system segments the frequency spectrum into distinct bands handled by specialized drivers. The balanced-armature driver handles high-frequency noise cancellation while the dynamic driver handles low-frequency components, allowing each component to remain relatively simple while achieving complex overall performance through division of labor.
Solution Approach 2:
The patent changes the operational parameters of the drivers by using a crossover network to direct different frequency ranges to appropriate drivers. This parameter-based allocation allows bandwidth-limited drivers to operate within their optimal ranges while still achieving broad-spectrum noise cancellation effectiveness.
3Ease of manufacture
If single-driver systems are used, then manufacturing cost can be reduced, but noise cancellation effectiveness deteriorates due to high latency in response
Solution Approach 1:
By segmenting the frequency response requirements across multiple drivers, the system reduces the processing burden on each individual driver. The balanced-armature driver focuses only on high-frequency components, enabling faster response times and reduced latency compared to a single driver attempting to handle the entire frequency spectrum.
Solution Approach 2:
The crossover network performs preliminary frequency separation before the audio signals reach the drivers. This pre-processing action divides the workload in advance, allowing each driver to respond more quickly to its designated frequency range without waiting for complex full-spectrum processing.
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 system effectively cancels noise by minimizing the error between noise and anti-noise, improving noise cancellation in ambient noise environments, particularly for high-frequency sounds, enhancing user experience in noisy conditions.
Implementation Method 1
an error microphone receiving audio from both low-frequency and high-frequency drivers
Implementation Method 2
outputting, using a first, low-frequency driver, first audio and outputting, using a second, high-frequency driver, second audio corresponding to the first output audio data
Data Source
AI summary
A system and method includes a loudspeaker having a first, low-frequency driver and a second, high-frequency driver. An error microphone is disposed near the loudspeaker and receives sound output by both drivers as well as noise. An estimation of the secondary path between the drivers and the microphones is determined, and playback audio is applied to the estimation. The output of the estimation is subtracted from the output of the microphone to determine anti-noise. This anti-noise is used to modify audio data sent to the first, low-frequency driver; the audio data is sent directly to the second, high-frequency driver.