Auditory-Space-Optimized Transfer Functions for Headphone Spatial Audio

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Solution Overview

Problem

Current audio playback systems using headphones fail to accurately simulate spatial audio due to 'in-head localization', where phantom sound sources lack direction and distance perception, diverging from the intended acoustic scene, and do not account for user expectations and room acoustics effectively.

Innovation Solution

A device determines 'listening room-optimized transfer functions' based on room acoustics analysis, combining outer ear transfer functions (HRTFs) with room-related transfer functions (RRTFs) to create binaural room impulse responses (BRIRs), which adapt audio signals to match the listening room's characteristics, enhancing spatiality and plausibility during playback.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If binaural synthesis with HRTFs is used for headphone playback, then spatial perception is improved, but in-head localization occurs and externality is reduced

Engineering Contradiction:
Improvespatial perceptionVSAvoidexternality
Core Design Contradiction:
Illumination intensityVSReliability

Solution Approach 1:

The patent combines HRTFs (head-related transfer functions) with RRTFs (room-related transfer functions) to create integrated binaural room impulse responses. This merging allows the system to simultaneously provide spatial perception through HRTFs and externality through RRTFs, resolving the contradiction between improved spatial perception and maintained externality in headphone playback.

Inventive Principle:
Principle #5Merging (Combining)

2Device complexity

If classic stereo reproduction is used with headphones, then device simplicity is maintained, but in-head localization occurs and direction information is lost

Engineering Contradiction:
Improvereproduction systemVSAvoiddirection information
Core Design Contradiction:
Device complexityVSLoss of information

Solution Approach 1:

The patent introduces RRTFs as an intermediary element that bridges the gap between simple headphone playback and complex spatial reproduction. By incorporating room-related transfer functions as a mediator, the system adds direction information and external perception without requiring complex loudspeaker setups, thus maintaining device simplicity while recovering lost directional cues.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Illumination intensity

If loudspeaker systems are used for audio playback, then spatial realism is improved, but portability and ease of use are reduced

Engineering Contradiction:
Improvespatial realismVSAvoidportability
Core Design Contradiction:
Illumination intensityVSEase of operation

Solution Approach 1:

The patent creates a virtual copy of the loudspeaker listening experience by using RRTFs to simulate room acoustics and spatial characteristics through headphones. Instead of requiring physical loudspeakers, the system copies the essential spatial and room-related acoustic properties into digital transfer functions that can be applied during headphone playback, thereby maintaining spatial realism while preserving portability.

Inventive Principle:
Principle #26Copying

Data Source

PatentEP3149969B1Determination and use of auditory-space-optimized transfer functions
Publication Date: 2019.09.18 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV
  • EP3149969B1 patent drawingFigure 1A
  • EP3149969B1 patent drawingFigure 1B
  • EP3149969B1 patent drawingFigure 2A

AI summary

The invention relates to a device for determining transfer functions that are auditory-space-optimized for a listening space, which device is used for the auditory space-optimized post-processing of audio signals during spatial reproduction. Said device is designed to analyze space acoustics of the listening space (12) and, on the basis of the analysis of the space acoustics, to determine the auditory-space-optimized transfer functions for the listening space in which the spatial reproduction should occur by means of a binaural near-field sound transducer. The spatial reproduction of the audio signals by means of the binaural near-field sound transducer can then be emulated with the aid of known head-related transfer functions and with the aid of the auditory-space-optimized transfer functions, wherein a room to be synthesized can be emulated on the basis of the head-related transfer functions (HRTF) and wherein the listening space (12) can be emulated on the basis of the auditory-space-optimized transfer functions (TF).