Distance-Based Audio Processing for Parametric Speaker Systems
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Solution Overview
Problem
Parametric audio systems face challenges in providing balanced audio output as the volume of conventional audio sound waves diminishes faster with distance, while ultrasonic audio signals maintain consistent amplitude, leading to an unnatural listening experience.
Innovation Solution
Implementing a distance-based audio processing system that adjusts the amplitude and frequency of ultrasonic audio signals using a parametric audio processor, which determines the listener's distance and applies a transfer function to equalize the audio output from both ultrasonic and conventional speakers, mimicking the free space propagation loss of conventional sound waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If ultrasonic audio signals are used to maintain consistent amplitude over distance, then the amplitude stability is improved, but the naturalness of audio propagation is worsened because conventional sound waves naturally attenuate with distance
Solution Approach 1:
The system dynamically changes the amplitude parameter of ultrasonic audio signals based on detected listener distance. When the listener is far away, the system increases ultrasonic amplitude to compensate for lack of natural attenuation; when close, it reduces amplitude to prevent excessive volume. This parameter adjustment resolves the contradiction between maintaining amplitude stability and preserving natural propagation characteristics.
Solution Approach 2:
The system employs distance detection feedback to continuously monitor listener position and adjust ultrasonic signal amplitude accordingly. The feedback loop measures actual distance and uses this information to modulate the ultrasonic carrier amplitude, ensuring that the combined audio output from conventional and ultrasonic speakers maintains natural attenuation characteristics regardless of listener position.
2Reliability
If distance-based amplitude adjustment is applied to ultrasonic signals, then the balanced audio output is improved, but the system complexity increases due to additional processing requirements
Solution Approach 1:
The system uses a single distance detection mechanism that serves multiple functions: it determines listener position for amplitude adjustment, calculates appropriate transfer function parameters, and coordinates between conventional and ultrasonic audio channels. This multi-functionality reduces overall system complexity despite the added processing requirements for distance-based amplitude control.
Solution Approach 2:
The system introduces a transfer function as an intermediary mathematical model that simplifies the relationship between distance and required amplitude adjustment. Instead of implementing complex real-time audio processing algorithms, the system uses pre-calculated transfer functions that encode the desired amplitude characteristics, reducing processing complexity while maintaining balanced audio output.
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 solution ensures a balanced and natural audio experience by equalizing the volume and adjusting the amplitude of ultrasonic audio signals relative to conventional audio signals, compensating for the differing attenuation characteristics of each technology.
Implementation Method 1
a modulator configured to modulate the first audio channel signal onto an ultrasonic carrier to generate an audio-modulated ultrasonic 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
Self-demodulation, or down-conversion, occurs along the air column resulting in the production of an audible acoustic signal
Implementation Method 4
determining a distance of a listener relative to either or both of the ultrasonic speaker and the conventional audio speaker
Data Source
AI summary
A hybrid ultrasonic audio system includes one or more ultrasonic speakers and one or more conventional speakers. An optical imaging system may be used to automatically determine the distance of a listener relative to the audio system. Channel processors apply distance-related transfer function filters to one or more of the audio channels based on the determined distances to equalize the amplitude of the audio played by the ultrasonic speakers relative to the conventional speakers. Channel processors may further apply a phase or time delay to the audio channels to match the phase and time delay of the ultrasonic speaker audio to the conventional speaker audio.