Audio Loudness Estimation for Consistent Playback Volume

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Solution Overview

Problem

Audio playback devices, particularly in mobile devices, face challenges in maintaining consistent perceived loudness across different audio sources, such as speech and music, leading to user discomfort due to frequent volume adjustments.

Innovation Solution

A method and apparatus that determine a loudness estimate of an audio signal using loudness models, including digital and parametric filters, and adjust digital signal processing parameters to control the audio signal, ensuring consistent perceived loudness by differentiating between speech and music, and considering environmental audio filtering models.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If different audio sources (speech, music) are played at the same volume level, then the device operates with consistent volume settings, but the perceived loudness varies significantly causing user discomfort

Engineering Contradiction:

Improvevolume control consistencyVSAvoidperceived loudness consistency

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The patent replaces manual volume control (mechanical/user-driven) with an automatic loudness normalization system that uses digital signal processing and psychoacoustic models to adjust gain levels based on perceived loudness rather than raw signal amplitude

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system dynamically changes the gain parameter based on loudness estimates derived from psychoacoustic models, adjusting the amplification factor according to the perceived loudness of different audio sources rather than maintaining a fixed volume level

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If the device automatically adjusts volume to maintain consistent perceived loudness, then user comfort improves, but the system complexity increases due to loudness modeling requirements

Engineering Contradiction:

Improveuser comfortVSAvoidaudio processing complexity

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent introduces loudness estimation models (such as Zwicker's model or ITU-R BS.1770) as intermediary processing layers between the audio source and the volume control mechanism, which compute perceived loudness metrics to guide automatic gain adjustment

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system performs preliminary loudness analysis on audio sources before playback, pre-computing loudness metrics and determining appropriate gain adjustments in advance to ensure consistent perceived loudness from the start of playback

Inventive Principle:

Principle #10Preliminary action

3Manufacturing precision

If loudness estimation models are applied to all audio signals, then perceived loudness consistency is achieved, but processing time and computational resources increase

Engineering Contradiction:

Improveloudness estimation accuracyVSAvoidprocessing delay

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The patent applies loudness estimation selectively rather than uniformly to all audio signals, using simplified models for certain signal types or applying full psychoacoustic analysis only when necessary, thereby reducing overall computational burden while maintaining adequate loudness normalization

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS10523168B2Method and apparatus for processing an audio signal based on an estimated loudness

Publication Date: 2019.12.31 NOKIA TECHNOLOGIES OY

AI summary

An apparatus comprising at least one processor and at least one memory including computer program code. The at least one memory and the computer program code is configured to, with the at least one processor, cause the apparatus at least to determine a loudness estimate of a first audio signal, generate a parameter dependent on the loudness estimate; and control the first audio signal dependent on the parameter.