PWM Circuit Overtone Selection for Small Speaker Voice Quality
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Solution Overview
Problem
Existing voice reproduction devices face challenges in reproducing high-quality voice when the frequency band of the voice outputter does not match the frequency band of the voice data, leading to potential low-quality voice output, especially with small-sized speakers or buzzers that have limited frequency reproduction capabilities.
Innovation Solution
A circuit device that uses a PWM signal output circuit to generate PWM signals based on pseudo sound data, which incorporates overtones from a fundamental tone within the outputtable band of the sound outputter, allowing for the reproduction of sound that would otherwise be beyond the outputter's capabilities, thereby enhancing voice quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If band extension is performed using an overtone signal without considering the frequency characteristics of the voice outputter, then computation load of CPU is reduced, but high quality voice reproduction cannot be guaranteed when the frequency band does not match the outputter's capabilities
Solution Approach 1:
The patent changes the parameter of frequency band selection by identifying overtones that fall within the outputter's reproducible frequency band. Instead of using all overtones or a fixed band extension approach, the system selectively uses only those overtones whose frequencies match the outputter's capabilities, thereby maintaining voice quality while reducing computation.
Solution Approach 2:
The patent incorporates feedback by using frequency characteristic data of the voice outputter to guide the selection of overtones. The system retrieves stored frequency characteristic information and uses it to determine which overtones are suitable for reproduction, creating a closed-loop approach that ensures quality while managing computation load.
2Volume of moving object
If a small-sized speaker or buzzer with narrow frequency reproduction capability is used, then device size is reduced, but voice reproduction quality deteriorates when the frequency band of voice data does not match the outputter's outputtable band
Solution Approach 1:
The patent changes the frequency domain parameters of the voice signal by transforming it into an overtone domain representation. This allows the system to select and emphasize only those frequency components (overtones) that the small-sized outputter can reproduce, effectively adapting the signal characteristics to match the physical constraints of the device while maintaining perceived voice quality.
Solution Approach 2:
The patent segments the voice spectrum into fundamental tone and overtone components, then selectively processes only the overtone portions that fall within the outputter's reproducible band. This segmentation allows independent optimization of different frequency components according to the specific capabilities of the voice outputter.
Data Source
AI summary
A circuit device (100) includes a PWM signal output circuit (110) that outputs a PWM signal (SPWM) to a sound outputter (10), and a processing circuit (120) that controls the PWM signal output circuit (110). The frequency band that the sound outputter (10) can output is denoted as an outputtable band, and the frequency band lower than a lower limit of the outputtable band is denoted as a non-output low frequency band. The PWM signal output circuit (110) outputs a PWM signal (SPWM) based on pseudo sound data in which overtones, of a plurality of overtones of a fundamental tone belonging to the non-output low frequency band, that belong to the outputtable band are used.