  We want to understand the human capabilities to perceive amplitude
similarities between a haptic and an audio signal. So, four psychophysical
experiments were performed. Three of them measured the asynchrony JND (Just
Noticeable Difference) at the signals' attack, release and decay, while the
forth experiment measured the amplitude decrease on the middle of the signal.
All the experiments used a combination of the constant stimulus and staircase
methods to present two stimuli, while the participants' (N=12) task was to
identify which of the two stimuli was synchronized. The audiotactile stimulus
was defined using an stereo audio signal with an ADSR (Attack Decay Sustain
Release) envelope. The partial results reveal JNDs for temporal asynchrony of:
54ms for attack, 265ms for decay and 57ms for release. Also the results reveal
an amplitude decrease JND of 25\%. Although for decay the results were to
disperse, therefore we suspect that the participants were not able to the
changes on the haptic signal.
