DIN ISO 226:2006-04

Foreword
Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Formula for derivation of normal equal-loudness-level contours
  4.1 Deriving sound pressure level from loudness level
  4.2 Deriving loudness levels from sound pressure levels
Annex A (normative) Normal equal-loudness-level contours for pure
                      tones under free-field listening condition
Annex B (normative) Tables for normal equal-loudness-level
                      contours for pure tones under freefield
                      listening conditions
Annex C (informative) Notes on the derivation of the normal
                      equal-loudness-level contours
Bibliography

Gives combinations of sound pressure levels and frequencies of pure continuous tones which are perceived as equally loud by human listeners.