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IEC 60268-7: Headphone Electroacoustic Measurement — The Science Behind Frequency Response Curves
How the Frequency Response Curve on Every Headphone Box Is Precisely Measured
IEC 60268-7:2010 specifies headphone and earphone electroacoustic measurement methods. The core tool is the Ear Simulator — a precision acoustic coupler replicating human ear canal acoustic impedance (IEC 60318-4), converting sound pressure into quantifiable electrical signals.
| Measurement | Method | Typical Spec | Significance |
|---|---|---|---|
| Frequency Response | 20Hz–20kHz sweep, SPL | ±3dB(20Hz–20kHz) | Defines tonal “character” |
| THD | Distortion at specified f and SPL | <0.1%(1kHz,94dB) | Affects sound “purity” |
| Sensitivity | SPL at 1mW input | 95–115 dB SPL/mW | Determines how “easy to drive” |
Why different reviewers publish different frequency response curves? Because of different ear simulator coupling methods — circumaural coupler, intra-concha coupler, or HATS (Head and Torso Simulator including acoustic scattering effects). Different couplers can differ by ±5 dB in the 2–8 kHz range. Always check which ear simulator type was used before comparing frequency response curves.
TN Lab — A frequency response curve is not “absolute.” It depends on the ear simulator type used.
