Biomedical Engineering Reference
In-Depth Information
Directional Microphones
ple variations of directional microphones,
this chapter focuses on the general con-
cepts, advantages, and limitations related
to directional microphones. Figure 4-8
illustrates the sensitivity of a directional
microphone. To some degree, the use of
contemporary directional microphones
improves the SNR for the wearer, improv-
ing comfort and speech understanding
(Lurquin & Rafhay, 1996; Valente, Fabry,
& Potts, 1995; Wouters, Litière, & van
Wieringen, 1999). Even though there has
been debate regarding the appropriate-
ness of employing directional processing
for children, directional microphones
contribute to better understanding in
noise for children (Gravel, Fausel, Liskow,
& Chobot, 1999; Kuk, Jackson, Keenan,
Another hearing aid and implantable
device feature intended to improve the
signal-to-noise ratio (SNR) for the hear-
ing aid wearer is the directional micro-
phone. Presently, hearing aids employ
two types of microphone arrangements
to provide either directional or omni-
directional sensitivity. Omnidirectional
microphone arrays are designed to have
uniform sensitivity to sounds in all direc-
tions, while directional microphone
arrays provide variable sensitivity based
on direction. Typically, directional micro-
phones are more sensitive in front of the
wearer, assuming that the wearer is look-
ing at the speaker. While there are multi-
Figure 4-8.
the sensitivity of directional microphones.
the microphones are more sensitive to the person in
the shaded area in front of the listener than the person
behind the listener.
