Audio Frequency Spectrum Correction for Consistent Loudness Tone
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Solution Overview
Problem
The transition from analog to digital audio technology has led to inconsistent loudness levels across different content, causing users to constantly adjust volume, and existing standards are not well-implemented, resulting in a lack of consistent tone during playback.
Innovation Solution
An audio signal processing method and apparatus that corrects the frequency spectrum of audio signals by determining the difference between playback loudness and desired loudness, using a relationship between loudness and sound pressure for each frequency band, and applying a correction gain to maintain consistent tone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If content creators increase audio levels to improve perceived sound quality, then loudness increases, but tone consistency deteriorates and users must constantly adjust volume
Solution Approach 1:
The patent applies parameter changes by adjusting frequency spectrum parameters (gain values for different frequency bands) based on the measured loudness difference. The processor calculates a correction value based on the loudness difference and applies it to specific frequency bands, transforming the audio signal parameters to achieve consistent tone perception across different loudness levels
Solution Approach 2:
The patent implements feedback by measuring the actual playback loudness, comparing it with the desired loudness, and using this information to automatically adjust the frequency spectrum. The system continuously monitors loudness and applies real-time corrections to maintain consistent tone, eliminating the need for manual volume adjustments by users
2Measurement precision
If different loudness measurement standards are used for different countries, then local measurement accuracy improves, but international compatibility deteriorates
Solution Approach 1:
The patent achieves universality by designing a loudness correction system that can work with different measurement standards. The processor calculates loudness based on the audio signal properties and applies corrections that are independent of the specific measurement standard used, allowing the same correction algorithm to function across different countries and standards
Data Source
AI summary
An audio signal processing apparatus is provided. The audio signal processing apparatus includes an input terminal receiving an input audio signal, a processor obtaining a difference between a playback loudness of the input audio signal and a desired loudness thereof and correcting a frequency band spectrum of an output audio signal for each of a plurality of frequency bands based on the difference between the playback loudness and the desired loudness of the input audio signal and a relationship between a loudness and a sound pressure for each of the plurality of frequency bands, and an output terminal outputting the output audio signal. The playback loudness is a loudness of the output audio signal when the input audio signal is output without the correction.