Methods - Soundscape Ecology: Principles, Patterns, Methods and Applications - page 234

Fig. 9.11 Schematic
representation of recording
procedures by using a single
microphone, or a set or an
array of microphones

The single microphone collects sounds without associating information about
the origin of sound, whereas a set of oriented microphones allows discovering the
precise (geographic) origin of the acoustic source. Finally, the array allows us to
cover the sonic information of a wide area, which in turn depends on the distance at
which the microphones are placed.
For instance, to estimate bird species abundance, richness, and composition,
Cellis-Murillo et al. ( 2009 ) have designed a soundscape recording system (SRS)
based on four microphones placed at 90 , shielded with plastic dividers, and
oriented 30 from the horizontal plane, connected to two Sony DAT TCD-D8s.
This system offers the advantage of listening to the sound files in the laboratory in
playback and locating the direction of the sound with precision. With this device the
authors have compared data collected directly in the field with data collected in a
post-processing procedure.
In another study, a wireless sensor network composed of four nodes was located
in a neotropical rainforest of Chiapas, Mexico, by Collier et al. ( 2010 ) to perform an
acoustic localization. Each node had a subarray of four microphones spaced
16.97 cm apart with a tetrahedral configuration. The system was equipped with a
GPS, an acoustic emitter, a computer, a wireless 802.11 network interface, and a
smart lithium ion battery pack; all the devices were packed into a Pelican 1,150
case. The entire system was remotely handled with a laptop or a smart phone. The
system was able to localize antbirds using the sound in playbacks with an accuracy
of 0.199 and 0.445 m, respectively.
An array of eight microphones at a distance of 75 m was used by Mennill
et al. ( 2006 ) to locate acoustically the position of duetting rufous-and-white wrens
( Thryothorus rufalbus ) in a Costa Rica evergreen forest using playback songs. The
position of the loudspeakers was estimated with an accuracy of 2.82

0.26 m, and it
was possible to calculate the “male” and “female” loudspeakers with an error of
2.12 0.42 m, confirming the validity of the method. Minor errors have been a

consequence of imperfect functioning of the GPS under a thick vegetation cover.