Broadband factory noise loudness in phons far exceeds its measured dB level

Evidence

In the case outlined in Fig. 8.24, a calculated loudness NGD of 24 sone (GD) and a corresponding loudness level LNGD of 86 phon (GD) is found. The factory noise has a relatively broad spectrum, therefore quite a difference appears between the measured sound level of 73 dB or the A-weighted sound pressure level of 68 dB(A) on one hand and the calculated loudness level of 86 phon The approximation of critical bands by third-octave bands is only acceptable for frequencies above about 300 Hz. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1323

Categorization

• QUESTION: Why does a 73 dB noise calculate to 86 phon? The sone/phon relationship for broadband noise deserves closer study.
• SHARE: A colleague working on workplace noise regulation would care that a 73 dB factory noise computes to 86 phon — decibel measures badly underestimate perceived loudness for broadband sources.