Ultrasonic Speaker Gain Control for Stable Modulation Degree
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Solution Overview
Problem
Conventional ultrasonic speaker systems experience sound quality degradation when the sound volume level of the speech signal is changed, leading to deviations in modulation degree, resulting in decreased audible sound pressure and increased harmonic distortion.
Innovation Solution
Incorporating a controller that adjusts the gains of variable gain blocks to maintain a predetermined modulation degree, ensuring the sound volume level remains consistent by dynamically controlling the gains of the first and second variable gain blocks, even if the user adjusts the sound volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the sound volume level of the speech signal is changed, then the user can adjust the audio output level, but the modulation degree deviates from the predetermined value causing sound quality degradation
Solution Approach 1:
The controller monitors the gain of the first variable gain block and automatically adjusts the gain of the second variable gain block to maintain the modulation degree at the predetermined value. This feedback control mechanism ensures that when users adjust the sound volume, the system compensates by adjusting the carrier wave gain accordingly, preventing modulation degree deviation and maintaining optimal sound quality.
Solution Approach 2:
The system dynamically adjusts the gain of the second variable gain block based on the real-time gain setting of the first variable gain block. This dynamic control allows the modulation degree to remain constant despite changes in sound volume, resolving the contradiction between user-adjustable volume and precise modulation control.
2Manufacturing precision
If the gain of the first variable gain block is increased to maintain predetermined modulation degree, then the modulation quality is maintained, but the sound volume level deviates from user expectation
Solution Approach 1:
The controller uses feedback from the first variable gain block's gain setting to automatically adjust the second variable gain block, creating a balanced control system that simultaneously maintains both the predetermined modulation degree and the expected sound volume level.
Solution Approach 2:
The system changes the gain parameter of the second variable gain block in response to changes in the first variable gain block, allowing simultaneous optimization of both modulation degree consistency and sound volume control through coordinated parameter adjustment.
3Device complexity
If conventional ultrasonic speaker systems are used without gain control, then the structure is simple, but sound quality degrades when volume is adjusted
Solution Approach 1:
The controller implements feedback control by monitoring the first variable gain block's output and automatically adjusting the second variable gain block, ensuring that modulation degree remains at the predetermined value regardless of volume adjustments, thereby maintaining consistent sound quality without excessive structural complexity.
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 maintains excellent sound quality properties by keeping the modulation degree and sound volume level consistent, preventing deviations in audible sound pressure and harmonic distortion, thus providing a stable audio reproduction experience.
Implementation Method 1
ultrasonic actuator 104 converts the modulated signal to an acoustic wave of a finite amplitude level and radiates the acoustic wave of the finite amplitude level to a medium
Implementation Method 2
an ultrasonic speaker system that reproduces signal sound in an audiofrequency band, using non-linearity of a medium (e.g., air) to an ultrasonic wave
Data Source
AI summary
An ultrasonic speaker system has a first variable gain block, a modulation block, a second variable gain block, an ultrasonic actuator, and a controller, wherein the controller controls gain of the first variable gain block so that a modulation degree of a modulated signal becomes a predetermined value, and when the controller raises the gain of the first variable gain block, the controller lowers the gain of the second variable gain block, while when the controller lowers the gain of the first variable gain block, the controller raises the gain of the second variable gain block.