Stereo Audio Signal Correction for Sharper Attack Sound

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Solution Overview

Problem

Audio signals, particularly attack sounds from percussion instruments, are deteriorated during digitalization and compression, resulting in a mild tone with slower sound level rise due to factors like speaker coil windings, deformation, and high-frequency component cut-off.

Innovation Solution

An audio signal correction apparatus and method that utilize differential-value acquisition circuits to calculate correction coefficients for left and right audio channels, which are then used to correct digital audio signals by multiplying them with specific ratios, effectively enhancing the attack sound's steep rise and clarity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If digitalization and compression are applied to audio signals, then storage and transmission efficiency are improved, but attack sound quality deteriorates with slower sound level rise and mild tone

Engineering Contradiction:

Improvestorage and transmission efficiencyVSAvoidattack sound quality

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

A correction coefficient generation circuit is introduced as an intermediary component between the compressed audio signal and the output. This circuit calculates correction coefficients based on differential values from the compressed signal and applies them to restore attack sound characteristics, thereby mediating between the efficiency gains of compression and the quality requirements of attack sounds

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes the parameter of the audio signal by applying correction coefficients that modify the sound level rise characteristic. The correction coefficients are calculated to increase the slope of sound level rise in attack sounds, transforming the degraded parameter back toward its original state while preserving compression efficiency

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If speaker coil windings are reduced, then speaker manufacturing cost and complexity are reduced, but sound level rise speed decreases resulting in mild tone

Engineering Contradiction:

Improvespeaker coil complexityVSAvoidsound level rise speed

Core Design Contradiction:

Device complexityVSSpeed

Solution Approach 1:

The invention replaces the mechanical solution (increasing speaker coil windings to improve sound level rise speed) with a digital signal processing approach. By calculating and applying correction coefficients to the audio signal, the system achieves fast sound level rise without modifying the physical speaker construction, thereby substituting mechanical complexity with digital processing

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Manufacturing precision

If cone deformation is minimized, then speaker manufacturing precision is improved, but the ability to reproduce instantaneous attack sounds is reduced

Engineering Contradiction:

Improvecone deformation controlVSAvoidattack sound reproduction accuracy

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The correction coefficient generation circuit performs preliminary action by pre-calculating correction values based on the compressed audio signal characteristics before the signal is converted to analog form. This preliminary digital processing compensates for the speaker's limited ability to reproduce instantaneous attacks, ensuring accurate attack sound reproduction without requiring precise mechanical cone control

Inventive Principle:

Principle #10Preliminary action

4Productivity

If high-frequency components are cut off in digital compression, then compression efficiency is improved, but attack sound sharpness and dynamic characteristics are lost

Engineering Contradiction:

Improvecompression efficiencyVSAvoidhigh-frequency attack sound information

Core Design Contradiction:

ProductivityVSLoss of information

Solution Approach 1:

The correction coefficient generation circuit uses feedback by analyzing the compressed audio signal itself to generate correction coefficients. It calculates differential values from the compressed signal and uses this feedback information to determine the appropriate correction amount, thereby restoring attack sound characteristics without requiring the original uncompressed signal or additional high-frequency information

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS8989405B2Audio signal correction apparatus, audio signal correction method, and audio signal correction program

Publication Date: 2015.03.24 JVC KENWOOD CORP

AI summary

A first differential value is acquired between first current data and first previous data in an i number (i being a natural number) of sampling periods before the current data. A second differential value is acquired between second current data and second previous data in a j number (j being a natural number) of sampling periods before the current data. Both first data and both second data are of a first and a second digital audio signal, respectively, having a sound level of a digital stereo audio signal in the left and right channels, respectively. A first and a second correction coefficient are acquired by adding the first and second differential values at a first and a second ratio, respectively. The first signal is corrected by multiplying the first signal by the first correction coefficient. The second signal is corrected by multiplying the second signal by the second correction coefficient.