Fig. 6
From: Combined method of identification of free oscillations of perforated riffled plates

Riffled perforated vibration surfaces. (a) Basic; (b) with riffles; (c) dimensions of one unit.
From: Combined method of identification of free oscillations of perforated riffled plates

Riffled perforated vibration surfaces. (a) Basic; (b) with riffles; (c) dimensions of one unit.