Adaptive Audio Equalization for Listening-Level Spectral Balance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Audio signals experience perceived spectral imbalances due to human ear sensitivity to sound pressure level changes and age-related hearing loss, with existing equalization methods failing to accurately compensate at varying listening levels and in low bit-rate encoded audio.
Innovation Solution
A method using SPL-dependent adaptive equalization and listener-dependent equalization, combined with optional spectral bandwidth extension, dynamically adjusts audio signals to maintain perceived spectral balance by analyzing playback levels and hearing characteristics, ensuring accurate compensation across frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed equalization function (smiley-face EQ) is applied to compensate for perceived spectral imbalance, then perceived spectral balance at lower listening levels is improved, but over-compensation occurs at higher listening levels
Solution Approach 1:
The patent applies dynamics by making the equalization function adaptive rather than fixed. The EQ curve dynamically adjusts its parameters (boost amounts, frequency points) based on the actual listening level detected during playback. This allows the system to provide appropriate spectral balance compensation at each listening level, preventing both under-compensation at low levels and over-compensation at high levels.
Solution Approach 2:
The patent changes the parameters of the equalization function based on listening level. Specifically, it modifies the boost amounts and frequency points of the EQ curve according to the detected playback level. This parameter adaptation enables the system to optimize perceived spectral balance for each listening condition, resolving the contradiction between fixed EQ performance and adaptability.
2Use of energy by moving object
If sound pressure level is reduced to provide a comfortable listening experience, then overall loudness is improved, but perceived spectral balance deteriorates due to differential frequency attenuation
Solution Approach 1:
The patent applies preliminary anti-action by preemptively boosting frequencies that are prone to attenuation at lower listening levels. Before the listener experiences spectral imbalance, the system detects the reduced playback level and applies compensatory EQ adjustments to counteract the expected differential attenuation. This prevents the spectral balance deterioration from occurring in the first place, while maintaining comfortable listening levels.
Solution Approach 2:
The system changes the equalization parameters (boost amounts, frequency points) based on the detected playback level. When listening level is reduced, the EQ curve is adjusted to provide greater compensation in frequencies that attenuate more rapidly. This dynamic parameter adjustment maintains perceived spectral balance across varying listening levels while preserving listening comfort.
3Loss of substance
If high frequency content is filtered out during low bit-rate compression to save bandwidth, then file size is reduced, but perceived brightness and spectral balance deteriorate
Solution Approach 1:
The patent applies parameter changes by adjusting the equalization curve to compensate for high frequency losses in low bit-rate encoded audio. The system detects the reduced high frequency content and modifies the EQ parameters to boost these frequencies appropriately. This allows the system to maintain perceived spectral balance and brightness even when the audio has been compressed to save bandwidth.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An input audio signal is equalized to form an output audio signal on the basis of an intended listening sound pressure level, the output capabilities of a particular playback device, and unique hearing characteristics of a listener. An intended listening level is first determined based on the properties of the audio signal and a mastering sound level. The intended listening level is used to determine an optimal sound pressure level for the particular playback device based on its capabilities and any master volume gain. These two levels are used to determine how much louder to make individual frequencies based on data pertaining to human auditory perception, either standardized or directly measured. The audio is further compensated on the basis of hearing loss data, again either standardized or directly measured, after optionally extending the signal bandwidth. The final, compensated audio signal is sent to the playback device for playback.