Parametric Loudspeaker Dynamic Modulation Depth Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional parametric loudspeaker systems face inefficiencies and increased audible distortion due to fixed modulation depths, which result in unnecessary ultrasonic signal levels and bandwidth expansion, especially when reproducing low-level audio signals.
Innovation Solution
The system dynamically adjusts modulation depths using a dynamic level control function that reduces modulation offset for low audio signals, allows full modulation for high audio signals, and under-modulates for intermediate signals, thereby reducing ultrasonic bandwidth and maintaining minimal distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the modulation depth of the ultrasonic carrier signal is increased to enhance efficiency for low-level audio signals, then the overall efficiency of the parametric loudspeaker system is improved, but the bandwidth of the ultrasonic signal increases, potentially increasing audible distortion upon reproduction
Solution Approach 1:
The patent applies dynamics by making the modulation depth adjustable rather than fixed. The system dynamically changes the modulation depth based on the audio signal level: using higher modulation depth for low-level audio signals to improve efficiency, and reducing modulation depth for high-level audio signals to minimize audible distortion. This dynamic adjustment resolves the contradiction between efficiency and distortion across different operating conditions
Solution Approach 2:
The patent changes the modulation depth parameter according to the audio signal level. By varying this key parameter dynamically, the system optimizes efficiency when audio signals are low while controlling audible distortion when audio signals are high, thus resolving the technical contradiction between these two opposing requirements
2Device complexity
If the modulation depth remains small for low-level audio signals to maintain a simple system, then the system complexity is reduced, but the efficiency of the parametric loudspeaker system deteriorates
Solution Approach 1:
The system transitions from a static modulation depth approach to a dynamic one, where modulation depth automatically adjusts based on audio signal level detection. This dynamic control improves efficiency without requiring complex manual intervention, as the adjustment is performed automatically based on signal level measurements
Solution Approach 2:
The patent implements feedback by detecting the audio signal level and using this information to automatically adjust the modulation depth. This feedback mechanism enables the system to optimize efficiency dynamically without adding significant complexity, as the adjustment is driven by automatic detection and control based on the actual signal conditions
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 enhances the accuracy of audio signal reproduction while minimizing audible distortion and optimizing energy usage by adjusting modulation depths based on audio signal levels.
Implementation Method 1
one or more ultrasonic transducers for directing the ultrasonic carrier signal through the air along a selected projection path
Implementation Method 2
Due to the non-linear propagation characteristics of the air, the modulated ultrasonic carrier signal is demodulated as it passes through the air, thereby reproducing the audio signal along the selected projection path
Data Source
AI summary
Modulation systems and methods for use in parametric loudspeaker systems that can dynamically adjust modulation depths of ultrasonic carrier signals based on the levels of audio signals that the parametric loudspeaker systems are called upon to reproduce. The modulation systems and methods employ a dynamic level control function for determining a modulation offset that allows, (1) for low audio signal levels, a reduction of the modulation offset to obtain a reduced ultrasonic signal level, (2) for high level audio signals, full or maximum modulation of the ultrasonic carrier signal at an increased ultrasonic signal level, and, (3) for intermediate audio signal levels, under-modulation of the ultrasonic carrier signal at an intermediate ultrasonic signal level.