Multichannel Audio Loudness Scaling for Channel Audibility
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for adjusting the loudness of multichannel audio signals fail to preserve the relative perceived loudness between channels, leading to undesirable changes in spatial balance when scaling overall loudness, particularly affecting quieter channels which may fall below the hearing threshold.
Innovation Solution
The method involves scaling the perceived loudness of each individual channel by a common amount to achieve a desired overall loudness adjustment, while optionally applying correction factors to minimize errors in loudness scaling, thereby preserving the spatial balance and timbre.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single gain is applied to all channels to scale overall loudness, then the overall perceived loudness is adjusted efficiently, but the relative perceived loudness between channels changes, causing spatial balance to deteriorate
Solution Approach 1:
The patent divides the audio signal into separate channel components and processes each channel individually. By calculating and applying separate gains to each channel based on its specific loudness characteristics, the method preserves the relative perceived loudness between channels while still achieving overall loudness scaling, thus resolving the contradiction between processing efficiency and spatial balance preservation.
2Power
If the overall sound pressure level is reduced, then the loudness scaling achieves the desired lower level, but quieter channels drop below the hearing threshold and become inaudible
Solution Approach 1:
The patent applies different gain adjustments to each channel based on its individual loudness characteristics and perceived importance. Quieter channels receive proportionally larger gain adjustments to maintain them above the hearing threshold, while louder channels receive smaller adjustments. This localized, channel-specific processing ensures that all channels remain audible after loudness scaling, resolving the contradiction between achieving desired overall level and maintaining channel audibility.
3Ease of operation
If traditional volume control is used to adjust loudness, then the operation is simple and intuitive, but the non-linear growth of perceived loudness causes timbre and spatial balance to change
Solution Approach 1:
The patent employs a feedback mechanism where the perceived loudness of each channel is continuously measured and used to determine appropriate gain adjustments. By monitoring the actual loudness characteristics and adjusting gains accordingly, the system maintains stable timbre and spatial balance while achieving desired loudness scaling, resolving the contradiction between operational simplicity and acoustic quality preservation.
Data Source
Figure 1~2
Figure 3~4a
Figure 4b~4c
AI summary
Scaling, by a desired amount s m,