Loudspeaker Protection via Distortion-Based Volume Limiting
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Solution Overview
Problem
Existing methods for protecting loudspeakers from damage due to peak sound power output levels fail to effectively monitor and control the maximum sound output level, leading to potential irreversible damage.
Innovation Solution
An audio testing system that includes an audio device under test, a microphone, an audio analyzer, and means to adjust and set the maximum volume, applying an audio test signal and incrementally increasing the output volume while measuring distortion to ensure the loudspeaker operates within a safe range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gain of low-frequency components is reduced to prevent excursion limit damage, then the risk of loudspeaker damage is reduced, but the maximum sound output level is not controlled and damage can still occur
Solution Approach 1:
The system uses a microphone to capture the actual sound output and feeds this signal back to an audio analyzer. The analyzer monitors the sound pressure level in real-time and compares it against predetermined safety thresholds, automatically adjusting the audio signal to prevent excursion limit damage while maintaining accurate sound output control.
Solution Approach 2:
The patent replaces manual equalizer adjustment and subjective volume control with an automated electronic monitoring and control system. The audio analyzer objectively measures sound pressure levels and automatically adjusts signal levels, replacing the need for manual mechanical adjustments and user judgment.
2Reliability
If the crossover frequency is increased to route low-frequency components to the woofer, then tweeter overload is prevented, but the sound output level is not monitored and damage can still occur
Solution Approach 1:
The system continuously monitors the actual sound output pressure level using a microphone and feedback loop. This real-time feedback enables the system to detect when the sound pressure approaches dangerous levels and automatically reduce the signal amplitude, providing objective control that complements the crossover frequency routing.
Solution Approach 2:
The patent introduces an audio analyzer as an intermediary between the audio source and the loudspeaker system. This intermediary device objectively measures the sound pressure level and automatically adjusts the signal to prevent both tweeter overload and excursion limit damage, serving as a mediator that protects the entire system.
3Ease of operation
If manual volume adjustment is used, then the device is simple to operate, but the maximum sound output level cannot be controlled to prevent damage
Solution Approach 1:
The system performs self-protection by automatically monitoring its own sound output and adjusting the signal level to prevent damage. The audio analyzer and feedback loop enable the device to self-regulate without requiring user intervention, making the system both easy to operate and reliably protective.
Solution Approach 2:
The automatic monitoring system uses feedback from the microphone to continuously assess the sound pressure level and adjust the signal accordingly. This creates a self-regulating system that maintains safe operating levels without requiring manual intervention, combining ease of operation with reliable protection.
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 ensures the loudspeaker operates at a volume below the damage threshold while setting the maximum volume to prevent damage, ensuring the device's sound output is controlled and safe.
Implementation Method 1
The at least one microphone is configured to receive the sound from the at least one loudspeaker and to output an electrical signal in response thereto
Data Source
Figure 1A~1C
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AI summary
The present invention provides a method (500) of testing and protecting a loudspeaker in an audio device under test, which comprises the loudspeaker. The method at least comprises adjusting (501) an output volume of the device under test to be initially substantially less than a maximum possible volume of the audio device, applying (502) an audio test signal to the audio device, emitting a sound from the loudspeaker in response to the audio test signal, receiving the sound from the loudspeaker with a test microphone, outputting an electrical signal from the microphone in response to the sound, and analysing (503) the electrical signal to measure a level of distortion in the sound emitted by the loudspeaker. If the measured level of distortion is found to be less than or equal to a maximum acceptable level of distortion, the method then comprises incrementally increasing (504) the output volume of the audio device and repeating the process of emitting a sound from the loudspeaker, receiving the sound with the microphone, outputting an electrical signal from the microphone and analysing (503) the electrical signal, until the measured level of distortion is greater than the maximum acceptable level of distortion. Then the method comprises stopping (505) the audio test signal, and determining (506) whether the output volume of the audio device is less than a least acceptable value of the maximum volume of the audio device. If so, the method comprises rejecting (507) the loudspeaker as out of specification. If not, the method comprises setting (508) the maximum volume of the audio device to be equal to the output volume of the audio device when the measured level of distortion was last less than or equal to the maximum acceptable level of distortion. The method ensures that the maximum volume of the audio device is set at a level below that at which damage to the loudspeaker can occur, whilst also ensuring that the maximum volume of the audio device is set to be more than a least acceptable value, by rejecting loudspeakers that are out of specification. The present invention also provides an audio testing system for carrying out such a method, and an audio device comprising at least one loudspeaker, which has been tested according to such a method.