Parametric Audio Carrier Amplitude Control for Squeal Masking
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Solution Overview
Problem
Conventional parametric audio reproduction systems produce unwanted high-pitched squeals due to subharmonics within the human audible range, limiting the carrier frequency and effective transmission distance, and the signal-to-noise ratio is not adequately managed to mask these squeals.
Innovation Solution
Adjust the amplitude of the ultrasonic carrier signal based on the amplitude of the audio signal to maintain an optimal signal-to-noise ratio, reducing or eliminating the perception of squeals by masking them with the audio signal, allowing for a lower carrier frequency and increased transmission distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the carrier frequency is reduced to mask subharmonic squeals, then the signal-to-noise ratio improves and squeal perception decreases, but the transmission distance is limited
Solution Approach 1:
The patent applies dynamics by making the carrier signal amplitude adaptive rather than fixed. The system dynamically adjusts the carrier amplitude based on real-time audio signal characteristics, increasing it when audio content is strong to mask squeals and reducing it when audio is weak to minimize transmission loss. This dynamic adjustment resolves the contradiction between maintaining high transmission distance and masking squeals.
Solution Approach 2:
The patent changes the parameter of carrier signal amplitude based on audio signal properties. By monitoring audio amplitude and adjusting carrier amplitude accordingly, the system optimizes the balance between transmission distance and squeal masking. When audio amplitude is high, carrier amplitude is increased to mask subharmonic squeals; when audio amplitude is low, carrier amplitude is reduced to maintain transmission efficiency.
2Length of moving object
If the carrier signal amplitude is increased to extend transmission distance, then the transmission range improves, but the signal-to-noise ratio deteriorates and squeals become more audible
Solution Approach 1:
The system dynamically adjusts carrier amplitude based on audio signal strength, preventing both excessive amplitude (which would cause audible squeals) and insufficient amplitude (which would limit transmission distance). The dynamic control ensures optimal balance between transmission range and squeal masking.
Solution Approach 2:
The patent implements feedback by monitoring audio signal characteristics and using this information to adjust carrier signal amplitude. The system continuously measures audio amplitude and adjusts carrier amplitude accordingly, creating a closed-loop control system that maintains optimal signal-to-noise ratio while masking squeals.
3Object-affected harmful factors
If the carrier signal amplitude is dynamically adjusted based on audio amplitude, then the signal-to-noise ratio is optimized and squeals are masked, but the system complexity increases
Solution Approach 1:
The system performs self-adjustment by automatically monitoring its own output characteristics and modifying carrier amplitude based on audio signal properties. The self-service mechanism eliminates the need for external manual adjustment or complex control systems, reducing overall system complexity while achieving effective squeal masking.
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
Enhances sound quality by minimizing squeals and extends the effective transmission range of parametric audio systems by dynamically adjusting the carrier signal amplitude in response to audio amplitude variations.
Implementation Method 1
Non-linear transduction results from the introduction of sufficiently intense audio-modulated ultrasonic signals into an air column. Self-demodulation, or down-conversion, occurs along the air column resulting in the production of an audible acoustic signal.
Implementation Method 2
When two sound waves with different frequencies are radiated simultaneously in the same medium, a modulated waveform including the sum and difference of the two frequencies is produced by the non-linear (parametric) interaction of the two sound waves.
Implementation Method 3
Parametric audio reproduction systems produce sound through the heterodyning of two acoustic signals in a non-linear process that occurs in a medium such as air.
Data Source
AI summary
A method for generating a modulated carrier signal that can be emitted as a parametric wave includes measuring an average amplitude of an audio signal, and adjusting an average amplitude of a carrier signal based on the average amplitude of the audio signal. The carrier signal is then modulated with the audio signal to generate a modulated carrier signal. Various circuits, components and software are also provided for implementing the modulated carrier signal generation scheme.