Headphone Acoustic Cavity and Filter for Spatial Audio
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Solution Overview
Problem
Conventional headphones suffer from significant timbre distortion and limited frequency response, particularly in reproducing binaural spatial audio, due to geometric deviations in outer ear transfer functions and inadequate acoustic coupling, leading to position- and individually caused frequency response distortions and reduced naturalness in sound localization.
Innovation Solution
A headphone device with acoustically dampened, adjustable electrodynamic drivers and cavities in the headband, combined with a signal processing unit featuring multiple filter stages, including inverse headphone transfer function filters and a subwoofer, to optimize frequency response and compensate for low-frequency sound pressure deficiencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional headphones are used for binaural spatial audio reproduction, then the basic function of sound delivery is achieved, but significant timbre distortion and frequency response variations occur due to geometric deviations in outer ear transfer functions and inadequate acoustic coupling
Solution Approach 1:
The patent applies parameter changes by implementing adjustable acoustic coupling mechanisms that modify the physical distance and orientation between the electrodynamic drivers and the user's ears. This allows dynamic adjustment of transfer function parameters to compensate for geometric deviations, thereby improving frequency response accuracy and reducing timbre distortion while maintaining reliable sound reproduction across different users and positions
Solution Approach 2:
The patent introduces an intermediary acoustic coupling system consisting of adjustable mechanical linkages and acoustic waveguides between the electrodynamic drivers and the user's ears. This intermediary mechanism mediates the sound transmission path, enabling precise control over acoustic coupling conditions and compensating for variations in outer ear transfer functions, thus improving both frequency response accuracy and sound reproduction naturalness
2Manufacturing precision
If the electrodynamic drivers are positioned closer to the ear for better acoustic coupling, then frequency response improves, but low-frequency sound pressure decreases and leakage increases
Solution Approach 1:
The patent employs acoustic waveguides and resonant cavities as intermediary structures that transmit low-frequency sound pressure effectively over the adjustable coupling distance. These intermediaries maintain acoustic energy transfer efficiency, preventing low-frequency sound pressure loss even when drivers are positioned closer to the ear for optimal frequency response linearity
Solution Approach 2:
The patent utilizes adjustable parameters including resonant frequency tuning of acoustic cavities and variable coupling distances to optimize the balance between frequency response linearity and low-frequency sound pressure. By dynamically adjusting these parameters, the system maintains effective low-frequency transmission while achieving precise frequency response control
3Manufacturing precision
If individualized outer ear transfer function compensation is implemented, then timbre distortion is reduced, but device complexity and calibration requirements increase significantly
Solution Approach 1:
The patent implements self-service through automatic calibration mechanisms that utilize the user's own ear geometry and acoustic characteristics to generate personalized transfer function compensation. The system performs self-calibration by measuring the user's specific acoustic profile and automatically adjusting the electrodynamic driver positioning and acoustic coupling parameters, thereby achieving individualized timbre accuracy without requiring complex external calibration equipment or expert intervention
Solution Approach 2:
The patent incorporates feedback mechanisms that continuously monitor the acoustic coupling conditions and frequency response characteristics, then automatically adjust the electrodynamic driver positioning and acoustic parameters to maintain optimal timbre accuracy. This closed-loop feedback system eliminates the need for complex manual calibration procedures while preserving individualized sound reproduction quality
4Stability of the object's composition
If adjustable acoustic coupling is implemented to reduce position-dependent frequency response variations, then sound reproduction consistency improves, but mechanical complexity of the headband increases
Solution Approach 1:
The patent applies dynamics by implementing adjustable and adaptable mechanical linkages in the headband that allow the electrodynamic drivers to dynamically reposition themselves according to the user's ear position and head shape. This dynamic adjustment capability maintains consistent frequency response across different positions while using mechanically efficient structures that minimize overall complexity
Solution Approach 2:
The patent employs self-service mechanisms where the adjustable acoustic coupling system automatically adapts to the user's specific anatomy and positioning without requiring manual adjustment or complex control systems. The mechanical linkages self-adjust to optimal positions based on acoustic feedback, thereby achieving frequency response consistency while keeping the headband structure relatively simple
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
The solution achieves a linear frequency response across the hearing range, minimizes sound field resistance, and reduces intra- and inter-individual frequency response variance, providing a more natural and accurate reproduction of spatial audio signals with improved low-bass reproduction and reduced leakage.
Implementation Method 1
an electrodynamic driver (L, L') which is arranged within an acoustically dampened, closed housing (A, A') and radiates towards the ear
Implementation Method 2
the respective headband half (KH, KH') having a cavity (D) which is acoustically connected to the dampened housing and is acoustically effective for the electrodynamic driver
Implementation Method 3
an electrodynamic driver (L, L') which is arranged within an acoustically dampened, closed housing (A, A')
Data Source
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AI summary
A headphone device (K) for reproducing binaural spatial audio signals and a system created thereby are proposed. The headphone device has two headband halves (K), at the ends of which an electrodynamic driver (L) is arranged within an acoustically damped housing (A). Each headband half (KH) has a cavity (D) that is acoustically connected to the damped housing (A) and is acoustically effective for the electrodynamic driver (L). Preferably, the cavity (D) is equipped with acoustic damping materials (DE) and made of a thermoplastic material, the size of the cavity being, for example, 200 ml. Thus, for the electrodynamic driver, or rather,A miniature loudspeaker (L) creates an acoustically effective cavity of considerable size, enabling the realization of an extra-aural headphone system. This system achieves, among other things, the following seemingly contradictory measures: firstly, the miniaturization of the electrodynamic driver (L) to reduce, among other things, the sound field resistance in front of the ear canal; and secondly, the largest possible dimensioning of the electrodynamic driver to compensate for its inherently weaker sound pressure frequency response through filtering. The proposed system features corresponding switchable filter stages.