Phase differences affect loudness only at low modulation frequencies the ear can track

Evidence

The difference between amplitude modulation (AM) and quasi-frequency modulation (QFM) holds only for conditions in which the ear is able to distinguish between the two different time functions of the envelopes. In this case, AM produces larger peak values and therefore larger loudness sensations than QFM. For modulation frequencies larger than about 10 Hz, the difference in phase of one component of the three-tone complex does not change loudness sensation. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1215