Exploring HRTF and headphone equalization
It seems that in this context, we're dealing with how blocked ear canal (BEC) affects measurements of ear canal resonances. For reproduction, we need to equalize headphones so they reproduce sound with the correct pressure. But since the ear canal isn’t physically blocked by headphones, there must be a way to align this pressure at a predefined target.
Comparing blocked vs. open ear canal measurements
Blocked ear canal (BEC) measurements offer less variability and are easier for standardization, but the mismatch comes from real conditions where the ear canal is open. On the other hand, open ear canal (OEC) measurements are closer to reality as they account for canal resonance and earphone coupling, but they’re trickier to get right. So, the system error difference depends on how we define it—likely as the pressure difference at the eardrum.
Defining "system error" in spatial audio
For minimal error, it's best to define the HRTF at the same reference point as reproduction. Most binaural technology uses blocked ear canal measurements for this, as they separate HRTF and ear canal effects. To get accurate eardrum pressure, though, you need ear canal transfer functions, which reduces spatial error. Open ear canal measurements, by contrast, are less reliable due to standing wave effects and exact placement sensitivity.
Distinguishing error metrics for system design
A blocked ear canal entrance measurement reduces mic placement sensitivity due to the boundary, leading to lower system error across listeners. If the goal is to recreate the pressure at the blocked canal entrance, then this method ensures consistency and smaller variability. But for targeting the eardrum, open-ear measurements may be more accurate at capturing the correct pressure there.
Clarifying system error in virtual soundfield reproduction
For virtual sound reproduction on headphones, if you measure or target the blocked ear canal entrance, the system error is typically lower and more consistent across users. While open canal measurements may reduce errors at the eardrum, they require precise measurement and equalization. Therefore, blocked canal is usually preferred for general-purpose HRTF libraries, whereas open ear canal or eardrum measurements are better for individual calibration, like with earbuds.
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