Strutt|Criteria|Curves|Sound Level|Equal Loudness inserts the equal-loudness curve for a pure tone sound into the current row of the workbook. The user may enter the phon value of the curve (i.e. the 1 kHz value) into Column D.
The user can choose to output the curve derived from ISO226:2003 (tonal curve), ISO226:1987 (tonal or random noise curve) or the Fletcher-Munson curve (tonal curve)
For ISO226 (1987): Entering 'MAF' into Column D returns the Minimum Audible Field (approximately 4.2 phon)
It is strongly recommended to use ISO 226:2003; ISO 226:1987 has been withdrawn and Fletcher-Munson is outdated.
Reference: ISO226 (2003) Acoustics - Normal equal-loudness level contours