Adaptive Noise Canceling Circuit Transducer Damage Prevention
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Solution Overview
Problem
Existing personal audio devices, such as wireless telephones, face challenges in providing effective noise cancellation in variable acoustic environments while preventing damage to the output transducer, as adaptive noise canceling circuits can be complex and power-consuming, and may generate undesirable results.
Innovation Solution
A personal audio device with an adaptive noise canceling (ANC) circuit that monitors the anti-noise signal levels to prevent damage to the transducer, incorporating a housing with a transducer for audio playback and anti-noise signal generation, an inference microphone for ambient sound measurement, and a processing circuit to adjust the anti-noise signal dynamically, ensuring effective noise cancellation without harming the transducer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adaptive noise canceling circuits are used to improve noise cancellation in variable acoustic environments, then noise cancellation performance is improved, but device complexity and power consumption increase
Solution Approach 1:
The adaptive noise canceling function is segmented into discrete operational modes (adaptive mode and non-adaptive mode) that can be independently controlled. The processing circuit selectively activates adaptive noise canceling only when beneficial, rather than continuously operating complex adaptive algorithms in all conditions, thereby reducing overall device complexity while maintaining noise cancellation performance where needed.
Solution Approach 2:
The system dynamically switches between adaptive and non-adaptive noise canceling modes based on real-time acoustic environment assessment. The processing circuit monitors ambient conditions and adaptively adjusts the noise canceling strategy, enabling the system to optimize performance while minimizing complexity by using simpler non-adaptive processing when environmental conditions permit.
2Reliability
If adaptive noise canceling circuits are used to improve noise cancellation, then noise cancellation performance is improved, but power consumption increases
Solution Approach 1:
The adaptive noise canceling operates periodically rather than continuously. The processing circuit evaluates acoustic conditions at intervals and activates adaptive processing only when the acoustic environment warrants it, thereby maintaining noise cancellation performance when needed while significantly reducing average power consumption during periods when adaptive processing is not required.
Solution Approach 2:
The system changes operational parameters by switching between adaptive and non-adaptive modes based on acoustic environment parameters. When ambient noise characteristics indicate that adaptive processing would be beneficial, the system transitions to adaptive mode; otherwise, it operates in lower-power non-adaptive mode, thus optimizing the balance between performance and power consumption.
3Reliability
If high levels of anti-noise signal are generated to effectively cancel ambient noise, then noise cancellation effectiveness is improved, but transducer damage risk increases
Solution Approach 1:
The processing circuit incorporates feedback monitoring of the anti-noise signal levels generated by the adaptive noise canceling circuit. By continuously monitoring the output signal characteristics and comparing them against safe operating thresholds, the system can detect when anti-noise signal levels approach dangerous magnitudes and take corrective action to prevent transducer damage while maintaining effective noise cancellation within safe limits.
Solution Approach 2:
The system implements protective measures in advance by monitoring anti-noise signal levels before damage can occur. The processing circuit is configured to detect potentially harmful signal levels and preemptively adjust or limit the anti-noise output, cushioning the transducer against damage before it can happen while still maintaining effective noise cancellation through alternative means or reduced gain.
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 solution effectively cancels ambient noise while preventing transducer damage by dynamically adjusting the anti-noise signal, ensuring reliable performance in changing acoustic environments with reduced power consumption and improved intelligibility.
Implementation Method 1
a transducer mounted on the housing for reproducing an audio signal that both source audio for playback to a listener and an anti-noise signal for countering the effects of ambient audio sounds
Implementation Method 2
A inference microphone is minted on the housing to provide a reference microphone signal indicative of the ambient audio sounds
Implementation Method 3
using signal processing to insert an anti-noise signal into the output of the device to cancel the ambient acoustic events
Data Source
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AI summary
A personal audio device, such as a wireless telephone, includes noise canceling circuit (30) that adaptively generates an anti-noise signal from a reference microphone signal (ref) and injects the anti-noise signal into the speaker or other transducer output to cause cancellation of ambient audio sounds. A processing circuit (60) monitors a level of the anti-noise signal, determines that the anti-noise signal may cause damage to the transducer and adjusts the generation of the anti-noise signal such that damage to the transducer is prevented.