Stig Ingamansson’s Noise Control: Principles and Practice 

B3 – Sound from Vibrating Plates – Size and Thickness 

A LONG, NARROW PLATE PRODUCES LESS SOUND THAN A SQUARE ONE 

When a plate is set into vibration, excess air pres— sure forms on one side of the plate and then the other. Sound comes from both sides. The pressure difference balances out close to the edges so that the radiation there is slight. Thus, a long, narrow plate radiates less sound than a square plate. 

Principle 

B4 – Sound from Vibrating Plates – Size and Thickness 

PLATES WITH FREE EDGES PRODUCE LESS LOW FREQUENCY NOISE 

If a plate vibrates with free edges, pressure equalization takes place between the two sides of the plate, thus reducing sound emissions. Enclosing the comers prevents pressure equalization and the sound emission is greater, especially at low frequencies. For example, loudspeakers produce more bass if they are enclosed in a cabinet. 

Principle