In-Ear Earphone Acoustic Correction via Eardrum Reflection Analysis
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Solution Overview
Problem
Conventional sound reproducing apparatuses using in-ear earphones face challenges in accurately measuring head-related transfer functions due to the earphone's speaker being directed inward, obstructing proper measurement, and relying on pseudo head characteristics for ear-canal correction, which affects the listening experience.
Innovation Solution
A sound reproducing apparatus that includes a measurement signal generating section, signal processing section, analysis section, and ear-canal correction filter processing section, which measures and analyzes signals with and without the earphone to obtain an ear-canal correction filter, allowing for convolution of sound source signals to simulate an unblocked ear canal experience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an in-ear earphone is worn in the ear, then the ear canal is blocked and the resonance frequency changes, but this causes the sound to become muffled and prevents obtaining a spacious sound
Solution Approach 1:
The patent creates a virtual copy of the unblocked ear canal acoustic environment through digital signal processing. By measuring the actual ear canal characteristics and generating a correction filter that replicates the acoustic response of an unblocked ear canal, the system reproduces the desired sound field without physically unblocking the ear canal.
Solution Approach 2:
The patent changes the acoustic parameters of the ear canal by using active noise control to generate anti-phase sound waves. This cancels the blockage effect and restores the resonance frequency characteristics to match those of an unblocked ear canal, thereby improving sound quality while the earphone remains in place.
2Ease of manufacture
If a conventional sound reproducing apparatus uses pseudo head characteristics for ear-canal correction, then the correction is based on average data, but this fails to provide accurate individualized correction
Solution Approach 1:
The patent enables the user's own ear canal characteristics to be measured and used for correction. The system automatically measures the individual's ear canal acoustic properties and generates a personalized correction filter, eliminating the need for manual input or reliance on average pseudo head data.
Solution Approach 2:
The patent implements a feedback mechanism where the measured ear canal characteristics are used to generate a correction filter that is then applied to the sound output. The system continuously adapts to the individual's specific ear canal geometry and acoustic properties, providing accurate personalized correction.
3Productivity
If the earphone's speaker is directed toward the inside of the ear for reproduction, then sound can be delivered effectively, but the speaker becomes an obstacle that prevents proper measurement of head-related transfer function
Solution Approach 1:
The patent introduces an intermediary measurement process that separates the reproduction function from the measurement function. A measurement signal is generated and processed through the earphone system, and the reflected signal from the eardrum is captured and analyzed to extract head-related transfer function characteristics without interfering with the normal sound reproduction path.
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 enables an optimal ear-canal correction filter to be obtained using an earphone, resulting in a listening state equivalent to not wearing an earphone, even when wearing one, by accurately simulating the ear canal's acoustic characteristics.
Implementation Method 1
measures, with the in-ear earphone, the signals reflected by an eardrum of the listening person by using a microphone function
Implementation Method 2
convolves a sound source signal with the filter, when sound is reproduced from a sound source signal
Data Source
AI summary
First, in a state where a pair of earphones 110 are worn in both ears of a listening person, a measurement signal generated by a measurement signal generating section 101 is outputted from the earphone 110. The signal (wearing-state signal) which is reflected by an eardrum and returns to the earphone 110 is measured, and stored in an analysis section 108. Next, in a state where the pair of earphones 110 are not worn in both ears of the listening person, a signal measured (unwearing-state signal) in the same manner as described above is stored in the analysis section 108. The analysis section 108 calculates an ear-canal correction filter based on a difference between the wearing-state signal and the unwearing-state signal. An ear-canal correction filter processing section 109 convolves a sound source signal with the calculated ear-canal correction filter.