When inserting an in-ear headphone (or earphone) in users ears, it is loaded by a range of ear canal geometries and eardrum impedances which interact with the output impedanc of the sound source. As a result, the ear canal transfer function between the ear tip and eardrum exhibits ear canal resonances above 1 kHz that may vary by one octave for the first resonance and around 10 dB between ears. The target responses for music reproduction and hear-through, which were originally tuned in an ear simulator, are thus altered at the users ears. We propose a new approach without making assumptions about ear canal geometry or eardrum impedance. The relationship between voltage, pressure and volume velocity of the earphone, which includes an in-ear microphone, are first characterized to turn the device into a pressure-volume velocity sensor. Then, the response of the in-ear microphone which is affected by the acoustic loading of the individual ear is used to calculate the input impedance of the ear. This ear impedance is then used to reconstruct the ear canal transfer function from the ear tip up to the users eardrum. Finally, the response at the users eardrum can be estimated knowing the pressure at the ear tip and this ear canal transfer function. Results in Type 2 and Type 4.3 artificial ears showed a high accuracy up to 9 kHz. They are compared to other estimations in human ears.
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