User-Specific HRTF Determination via Pinna Geometric Modeling

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Solution Overview

Problem

Existing methods for generating head-related transfer functions (HRTFs) are time-consuming and impractical for user-specific applications, often resulting in incomplete HRTF information due to the need for direct physical measurements or complex imagery-based calibration processes.

Innovation Solution

A device and method that use a structured-light scanner to capture three-dimensional images of a user's pinna, combining visible and hidden feature data through geometric models and reference databases to determine a user-specific HRTF, which can be applied to audio signals for accurate spatial audio rendering.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If direct physical measurements of the pinna are used to generate HRTF, then measurement precision is improved, but device complexity and cost increase due to requiring special laboratory instruments

Engineering Contradiction:

ImproveHRTF measurement accuracyVSAvoidmeasurement equipment complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent uses imagery tools (cameras, structured light scanners) to create visual copies of the pinna instead of direct physical contact measurements. This allows indirect measurement of pinna geometry through optical fields, eliminating the need for specialized laboratory instruments while maintaining measurement capability

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent replaces mechanical measurement systems (physical contact probes, laboratory equipment) with optical field-based systems (cameras, structured light). This substitution transforms the measurement approach from mechanical to optical, reducing device complexity and enabling user-specific HRTF measurement without specialized equipment

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If imagery tools are used to measure the pinna, then ease of operation is improved, but measurement precision deteriorates due to inability to capture hidden features

Engineering Contradiction:

Improvemeasurement process simplicityVSAvoidpinna feature completeness

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent performs preliminary actions by having the user assume multiple predetermined poses (front-facing, profile views, etc.) before measurement. This allows imagery tools to capture different angles and aspects of the pinna, including features that would be hidden in a single pose, thereby improving measurement completeness while maintaining ease of operation

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent adds the temporal dimension by capturing images across multiple time points (different poses). This transforms a static 3D measurement problem into a dynamic multi-view problem, allowing reconstruction of complete pinna geometry including hidden features through synthesis of multiple 2D images taken from different angles

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Adaptability or versatility

If user-specific HRTF measurement is performed on a user-by-user basis, then adaptability is improved, but productivity deteriorates due to time-consuming measurement processes

Engineering Contradiction:

Improveuser-specific customizationVSAvoidHRTF generation speed

Core Design Contradiction:

Adaptability or versatilityVSProductivity

Solution Approach 1:

The patent uses partial action by measuring only the critical pinna features that most significantly impact HRTF, rather than attempting complete comprehensive measurement. This selective approach reduces measurement time and complexity while still achieving user-specific customization. The system captures essential geometric data needed for HRTF generation without requiring exhaustive measurement of all possible features

Inventive Principle:

Principle #16Partial or excessive action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enables efficient and accurate generation of user-specific HRTFs for personalized spatial audio experiences, overcoming the limitations of traditional measurement methods by incorporating both visible and hidden pinna features, thus providing a more realistic sound simulation.

Implementation Method 1

a structured-light scanner to capture three-dimensional images of a user's pinna

Methodology Applied

Scientific EffectLight reflection: Reflection

Data Source

PatentUS11315277B1Device to determine user-specific HRTF based on combined geometric data

Publication Date: 2022.04.26 APPLE INC

AI summary

A device and a method of using the device to determine a user-specific head-related transfer function (HRTF), are described. The device can determine first geometric data corresponding to visible features of a pinna of a user in an image, and second geometric data corresponding to hidden features of the pinna obfuscated by the visible features in the image. The first geometric data and the second geometric data are combined in a geometric model that describes a shape of the pinna, and the user-specific HRTF is determined based on the geometric model. The user-specific HRTF is used to render spatial audio to the user. Other aspects are also described and claimed.