Non-occluding Active Noise Shaping via Acoustic Delay
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Solution Overview
Problem
Traditional active noise suppression headphones suffer from occlusion, which causes discomfort and affects the auditory experience by blocking the ear canal and altering sound transmission, leading to muted self-voice and attenuated high frequencies, and fail to allow unattenuated desired sound to pass through.
Innovation Solution
A non-occluding active noise shaping apparatus with an acoustic path and an electronic path that includes an ambient microphone, audio processor, speaker, and acoustic delay line, which couples ambient air pressure directly into the ear canal while using destructive interference to cancel ambient noise, and optionally includes a passive low-pass filter and internal microphone to enhance sound clarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional active noise suppression headphones use occluding ear canal blocking, then noise cancellation effectiveness is improved, but auditory experience deteriorates due to muted self-voice and attenuated high frequencies
Solution Approach 1:
The invention divides the sound transmission path into two separate channels: an acoustic path that remains open for natural sound transmission (including self-voice and high frequencies), and an electronic path that processes ambient noise for cancellation. This segmentation allows noise cancellation to function effectively while preserving natural auditory experience through the open acoustic path.
Solution Approach 2:
The invention introduces an acoustic delay line as an intermediary component in the acoustic path to delay ambient sound by approximately 1-5 milliseconds. This delay allows the electronic noise cancellation path to process and cancel noise before the delayed ambient sound reaches the ear, enabling effective noise suppression without occlusion.
2Reliability
If occluding ear canal blocking is used, then noise isolation is improved, but comfort deteriorates due to pressure fluctuations and vertiginous feelings
Solution Approach 1:
The invention segments the sound path into acoustic and electronic channels, allowing the acoustic path to remain open for natural pressure equalization and comfortable sound transmission, while the electronic path handles noise cancellation. This eliminates the occlusion effect that causes discomfort and vertigo.
Solution Approach 2:
The invention replaces the mechanical occlusion-based noise isolation system with an electronic noise cancellation system. Instead of physically blocking the ear canal to isolate noise, the system uses electronic processing to generate anti-phase sound waves that cancel ambient noise, eliminating the mechanical occlusion that causes discomfort.
3Object-affected harmful factors
If open ear canal is used, then natural sound transmission is improved, but noise cancellation effectiveness deteriorates
Solution Approach 1:
The acoustic delay line acts as an intermediary that delays ambient sound in the acoustic path, allowing the electronic noise cancellation path to process and cancel noise before the delayed ambient sound arrives at the ear. This timing coordination enables effective noise cancellation with an open ear canal.
Solution Approach 2:
The electronic noise cancellation path performs preliminary noise cancellation before the ambient sound reaches the ear through the acoustic path. By processing and canceling noise in advance, the system ensures effective noise suppression while maintaining natural sound transmission through the open acoustic channel.
4Reliability
If passive attenuation structures are used, then high frequency noise reduction is improved, but desired sound transmission deteriorates due to broadband attenuation
Solution Approach 1:
The invention segments noise reduction into frequency-specific paths: passive attenuation structures handle high frequency noise reduction, while the open acoustic path preserves desired sound transmission including high frequencies. The electronic noise cancellation path supplements this by handling low frequency noise, creating a comprehensive frequency-specific noise reduction system.
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 effectively reduces occlusion by allowing ambient air pressure to couple directly into the ear canal, enhancing sound clarity and reducing discomfort, while maintaining effective noise cancellation across a wide frequency range.
Implementation Method 1
an acoustic delay line, which delays sound in the acoustic path by about 1-5 milliseconds
Implementation Method 2
which couples ambient air pressure directly into the ear canal while using destructive interference to cancel ambient noise
Data Source
AI summary
Non-occluding active noise suppression apparatus and methods are disclosed. A housing includes an inlet to admit ambient sound and an outlet to output personal sound to the ear of a user. An acoustic path and an electronic path are provided from the inlet to the outlet within the housing. For a predetermined frequency range, a phase difference between the acoustic path and the electronic path is substantially 180 degrees.