Magnitude estimation with an anchor uses a fixed 70 dB car sound as reference.

Evidence

This demonstration illustrates the method of magnitude estimation with anchor sound. Four pairs of stimuli are presented. The first sound in each pair, called anchor sound, is always an excerpt of a car sound with 70 dB. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 3247