Open-Ear Microphone Placement Using Acoustic Nulls
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Solution Overview
Problem
Existing wearable audio devices, such as off-ear headphones, face challenges in delivering audio to the ear canal without obstructing it and effectively reducing noise interference, which affects the user experience and acceptance, particularly for those hesitant to use hearing aids.
Innovation Solution
The design of a head-worn acoustic device with acoustic transducers and microphones positioned to minimize coupling and include echo cancellation and active noise reduction circuits, allowing for directional audio capture and improved signal-to-noise ratio, enhancing speech intelligibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the acoustic transducer is positioned close to the ear canal for effective audio delivery, then audio delivery efficiency is improved, but coupling between the transducer and microphone increases causing noise interference
Solution Approach 1:
The patent introduces an acoustic null as an intermediary zone between the acoustic transducer and the microphone. By positioning the microphone in the acoustic null region, the harmful acoustic coupling is blocked while allowing the transducer to effectively deliver audio to the ear canal. This intermediary spatial zone resolves the contradiction by enabling close proximity without direct coupling.
Solution Approach 2:
The patent applies local quality by creating a specific acoustic environment (acoustic null) at the microphone's location while maintaining strong acoustic output toward the ear canal. The acoustic transducer produces different acoustic characteristics in different spatial directions - strong sound toward the ear and minimal sound at the microphone position, allowing optimized performance for both audio delivery and noise reduction.
2Measurement precision
If the microphone is positioned close to the acoustic transducer for effective audio capture, then audio capture quality is improved, but coupling between transducer and microphone increases
Solution Approach 1:
The acoustic null serves as an intermediary that allows the microphone to be positioned close to the transducer for effective audio capture while preventing direct acoustic coupling. The null zone acts as an acoustic barrier that enables proximity without interference.
Solution Approach 2:
The acoustic null is pre-configured in the spatial arrangement before operation begins. This beforehand cushioning of acoustic interference allows the system to operate with close spacing between transducer and microphone without suffering from coupling problems during actual use.
3Ease of operation
If open-ear configuration is used to avoid obstructing the ear canal, then user comfort and acceptance are improved, but noise interference and signal-to-noise ratio deteriorate
Solution Approach 1:
The acoustic null acts as an intermediary that enables the open-ear configuration to maintain user comfort while preventing noise interference. By strategically positioning the microphone in the null zone, the system achieves both unobstructed ear canal access and effective noise reduction.
Solution Approach 2:
The patent employs echo cancellation and active noise reduction circuits that use feedback from the microphone to compensate for noise interference. The system continuously monitors the acoustic environment and adjusts signals to maintain high signal-to-noise ratio while preserving the open-ear comfort advantage.
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 provides at least 5 dB improvement in signal-to-noise ratio and improved speech intelligibility, making open-ear devices more acceptable for users by reducing noise interference and enhancing audio delivery.
Implementation Method 1
a lobe of a radiation pattern of the at least one acoustic transducer is directed towards the ear canal of the user, and the at least one microphone is positioned in an acoustic null in a radiation pattern of the at least one acoustic transducer
Implementation Method 2
an echo cancellation circuit configured to process the signals representing the audio captured using the at least one microphone to generate a second signal for the at least one acoustic transducer, wherein a combination of the first signal and second signal reduces coupling between the at least one acoustic transducer and the at least one microphone by at least 3 dB
Implementation Method 3
produce sound using an electro-acoustic transducer that is spaced from the user's ear canal entrance
Implementation Method 4
at least one microphone configured to capture audio that is processed and played back through the at least one acoustic transducer
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
A head-worn acoustic device includes at least one acoustic transducer disposed such that, in a head-worn state, the transducer is in an open-ear configuration in which an ear canal of a user of the head-worn acoustic device is unobstructed. The acoustic device also includes at least one microphone configured to capture audio that is processed and played back through the transducer, and an amplifier circuit configured to process signals representing the audio captured using the microphone and generate driver signals for the transducer. The transducer and the microphone are disposed on the head-worn acoustic device such that, in the head-worn state, a lobe of a radiation pattern of the at least one acoustic transducer is directed towards the ear canal of the user, and the at least one microphone is positioned in an acoustic null in a radiation pattern of the at least one acoustic transducer.