Electronic Supply by Industrial Electronics in Milwaukee Wisconsin : Potter Brumfield, Radio Shack Stores in Milwaukee: Why Different Sounds Are Different

Why Different Sounds Are Different
================================================================================
Staff  on 23/12/2009 20:23:00

To discover the operational differences between electro-magnetic and
piezo-ceramic transducers, let's return to the design process of each and then
determine how each device will vary the sound. The first operational difference
between the two devices exists in how the base material is made to deflect.

The electro-magnetic device creates the deflection by applying an oscillating
voltage to a coil that,
during the positive half cycle, pushes away or deflects the thin base material
which is mounted on top of the magnet. The base material is then brought to its
original position during the magnetic half cycle by a magnetic field. Thus, the
base material vibrates at the frequency of the applied signal, causing
vibrations in air pressure, or sound.
Piezo-ceramic devices deflect with the application of an oscillating voltage.
The piezo crystal is
mounted to a metal base within a sound chamber. The drive circuitry supplies an
oscillating signal to the crystal which causes it to deflect. As previously
mentioned, the deflections of the piezo cause changes in the air pressure within
the sound chamber, creating the audible sound. The sound output will be at the
frequency of the oscillating signal supplied by the drive circuit. No
electro-magnetic or RF noise is created with piezo devices.
The popular Mallory Sonalert(R) is a good example of a piezo-ceramic audible
alarm. It is simple to
operate because it is self-contained, with the drive circuitry supplied within
the device. In addition, it is effectively sealed for use in harsh environments.
Models are available which operate at various voltages ranging from 1 VDC to 250
VAC.
Which is the right device for you? It depends entirely on your application and
the sound you anticipate it will take to accomplish your objective.