Open Audio Device Acoustic Cavity Resonance Matching
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Solution Overview
Problem
Open audio devices experience sound spillage due to unconfined acoustic transducers, which detract from their usefulness and desirability by allowing external sound leakage, particularly when resonance frequencies of the front and rear acoustic cavities are mismatched.
Innovation Solution
The design of an open audio device with acoustically coupled front and rear cavities, where the fundamental resonance frequencies are matched to minimize sound spillage, using resistive elements and acoustic transmission lines to direct sound effectively and damp resonances, and a removable accessory that adjusts audio signals based on its attachment status.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the acoustic transducer is spaced from the ear and does not confine the sound, then the user can be more aware of the environment and social cues are provided, but sound spillage increases and can be heard by others
Solution Approach 1:
The acoustic device is divided into separate front and rear acoustic cavities, each with independent sound-emitting openings. This segmentation allows the front cavity to deliver sound to the user while the rear cavity directs sound away from others, reducing spillage while maintaining environmental awareness.
Solution Approach 2:
The front and rear acoustic cavities are designed with asymmetric characteristics, including different resonance frequencies and sound emission directions. The front cavity is optimized for user listening while the rear cavity is optimized to direct sound away from bystanders, creating an asymmetric sound distribution pattern.
2Device complexity
If the front and rear acoustic cavities have mismatched resonance frequencies, then the device structure is simpler, but sound spillage increases and audio quality deteriorates
Solution Approach 1:
The resonance frequencies of the front and rear acoustic cavities are carefully matched through parameter optimization. By adjusting cavity volumes, opening areas, and transmission line lengths, the system achieves resonant frequency matching that minimizes sound spillage and improves audio quality.
Solution Approach 2:
The acoustic design incorporates feedback mechanisms where sound from the rear cavity is acoustically coupled back to the front cavity. This feedback loop helps cancel unwanted sound emissions and improves overall sound distribution, reducing spillage to bystanders.
3Object-generated harmful factors
If resistive elements are added to the sound-emitting openings, then sound spillage is reduced and resonance is damped, but device complexity increases
Solution Approach 1:
Resistive elements in the form of porous materials or screens are placed at the sound-emitting openings of both front and rear cavities. These porous structures provide acoustic resistance that dampens resonance and reduces sound spillage while maintaining a relatively simple overall device structure.
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
This approach reduces sound spillage by ensuring that sound pressure levels are evenly distributed, maintaining user comfort and audio quality while minimizing external noise leakage, with improved bass and loudness when the accessory is attached.
Implementation Method 1
an acoustic radiator that emits front-side acoustic radiation from its front side
Implementation Method 2
a second front sound-emitting opening that comprises a resistive element
Data Source
AI summary
An open audio device includes an acoustic radiator that emits front-side acoustic radiation from its front side and emits rear-side acoustic radiation from its rear side, a front acoustic cavity that receives front-side acoustic radiation, and a rear acoustic cavity that receives rear-side acoustic radiation. At least one sound-emitting opening is acoustically coupled to the front acoustic cavity or the second acoustic cavity. The open audio device also includes a removable accessory that includes an acoustic transmission line that is acoustically coupled to the at least one sound-emitting opening when the removable accessory is attached to the open audio device.