Download Knowles Electronics, Inc

Theory and Operations
Microphones measure sound
pressure. Inside an Emkay
microphone is a thin flexible
diaphragm, an electrically
charged plate, and an
amplifier (Fig. 1.). The output
voltage is proportional to
changes
in
the
small
separation
between
the
diaphragm and the charged
plate (Fig. 2).
FIG. 1.: Cross section of an Emkay EM microphone.
As sound pressure inside the front cavity
increases, the diaphragm is pushed
closer to the plate. As the pressure
decreases, it moves further away. The
motion of the diaphragm produces a small
electrical signal that is amplified by a
miniature circuit inside the microphone.
FIG. 2.: EM diaphragm and electret.
The sensitivity of a typical Emkay microphone is shown in Fig. 3. in units of dB relative to 1 Volt
per 0.1 Pascal. The microphone components can be modified to make it more or less sensitive
at lower frequencies or to reduce, increase, or shift the peak at higher frequencies.
FIG. 3.: EM sensitivity in dB relative to 1 volt per 0.1 Pa.
Emkay Innovative Products
1151 Maplewood Drive
Itasca, IL 60143
U.S.A.
Phone:
630-250-5930
Fax:
630-250-5932
Emkay Innovative Products
York Road, Burgess Hill
West Sussex, RH15 9TT
England
Phone:
44-1444-235432
Fax:
44-1-444-248724
www.emkayproducts.com
Emkay Innovative Products
53 Pao Hsing Road
Hsin Tien City, Taipei,
Taiwan (ROC)
Phone:
886-2-2911-4931
Fax:
886-2-2918-6868