EarEqual Reference Target
A technically motivated starting point for measurements made at the blocked ear-canal entrance. Version 0.1 is a preliminary universal reference, not a validated preference curve or a claim that one target is right for every listener or headphone.
v0.1 · 20 Hz to 20 kHzEarEqual measures at a different acoustic reference.
Conventional headphone targets such as Harman are normally defined at the eardrum or on artificial-ear measurement systems. The Plug measures at the blocked ear-canal entrance. Those target curves therefore cannot simply be copied across unchanged.
The EarEqual Reference Target is expressed for the same kind of blocked-entrance measurement made by the Plug.
Human blocked-ear data
The acoustic backbone is the published population-average diffuse-field response measured at the blocked ear-canal entrance in real human ears. It includes average head, pinna and concha effects at that reference point.
No downstream canal target
The target does not add the entrance-to-eardrum canal transfer. When the Plug is removed for listening, your own ear canal is physically back in the playback path.
Broad listening balance
A broad low-frequency shelf and gentle spectral tilt are added as practical listening-balance terms rather than as anatomical resonances.
For v0.1, the broad shaping is approximately a 5 dB low shelf around 105 Hz plus a −0.55 dB/octave tilt above 200 Hz. These values are a starting choice, not fitted perceptual constants.
Measure your own target.
If you can measure a loudspeaker or another acoustic reference with the Plug, that is the conceptually cleaner calibration. Measure the target and the headphones on the same listener, at the same reference point.
This avoids replacing your measured blocked-ear response with a population target. The measured target can be smoothed, windowed to control room reflections, or deliberately shaped afterwards.
A reference, not the final answer.
A universal blocked target still replaces individual head/pinna/concha differences with a population-average version. Also, the headphone can behave differently with the ear blocked during measurement and open during normal listening; this is most relevant for headphones that are sensitive to acoustic loading, including some closed-back designs.
Very high-frequency equalization is also sensitive to fit and placement. The 16 to 20 kHz end of v0.1 is smoothly extrapolated because the underlying blocked-ear population data end at 16 kHz.
One target cannot sound identical at every level.
Human frequency sensitivity changes with listening level. EarEqual v0.1 is intended as a neutral starting point for normal listening levels, not as a level-independent perceptual law. At quieter playback, additional low-frequency,and sometimes high-frequency,compensation may be preferred.
For now EarEqual provides one reference curve rather than several loudness-dependent targets. Level-dependent versions can later be expressed as adjustments around the same blocked-ear reference.
Where the rationale comes from.
- Hammershøi, D. & Møller, H. (1996), Sound transmission to and within the human ear canal, JASA 100(1), 408 to 427. The work separates free-field-to-blocked-entrance transmission, pressure division, and transmission along the ear canal.
- ISO 11904-1, Determination of sound immission from sound sources placed close to the ear, Part 1: Technique using a microphone in a real ear (MIRE technique). The published blocked-ear diffuse-field values are used as the population reference.
- Harman headphone-target research provides an important comparison for broad listening preference and spectral balance, but is defined in a different measurement domain.
- ISO 226 equal-loudness contours motivate the explicit note that a single target is not perceptually invariant with playback level.