Agriculture Reference
In-Depth Information
where
α
and
β
represent the amount of acoustic energy in the biophony (2-11
kHz) and anthrophony (1-2 kHz) frequency domains, respectively. The value of
NDSI can range between -1 (pure anthrophony) to 1 (pure biophony). The index
has exceptions: some vocalizing organisms such as large birds and amphibians
can produce sound within the anthropogenic frequency range, and geophony as
well as anthrophony (loud engines) can obscure sounds across the entire spec-
trum. However, the overall patterns in the soundscape represented by this index
can be used to characterize the soundscape both spatially and over time (Gage
and Axel 2013).
An Automated Acoustic Recording System
Prior to the development of automated acoustic recording technology, acous-
tic observations of birds and amphibians were made by visiting a habitat, listen-
ing for signals, interpreting them, and then recording their occurrence. By 2000
emergent technologies such as web cameras connected to the Internet were being
used to transmit visual observations and the capacity to make automated acoustic
observations quickly followed. However, file size associated with acoustic observa-
tion can be large and the use of wireless technology to transmit large files remains
challenging.
Soundscape recording at KBS LTER was initiated in 2001 using a desktop com-
puter in a field shed at the Main Cropping System Experiment (MCSE; Table 14.1)
(Robertson and Hamilton 2015, Chapter 1 in this volume). The computer was pro-
grammed to record, capture, and transmit recordings via the Internet to a remote
server on the Michigan State University (MSU) campus. A microphone on the out-
side of the shed captured recordings at regular intervals.
Use of Tape Recorders to Assess Biodiversity and Acoustic Variability
in KBS Habitats
Digitizing and quantifying sound recordings provide both a measure of the chang-
ing patterns of the soundscape in an ecosystem as well as the identification of vocal
species and a characterization of changes in biodiversity of vocal species com-
munities at various temporal and spatial scales (Qi et al. 2008, Joo et al. 2011). At
KBS, we recorded sounds in five MCSE communities—Alfalfa, Poplar, Coniferous
Forest, Mid-successional, and Deciduous Forest—from May 18 to July 15, 2005
(Fig. 14.2). These early observations of the soundscape were made using an analog
cassette tape recording unit that contained a clock to start and stop the recording
(Sangean VersaCorder
®
, C. Crane Co.) and an omni-directional boundary micro-
phone (Model 330-3020, Radio Shack Corp.). These units were placed at each
recording site and were set to turn on and off six times in a 24-hour period. The
6095 recordings collected using this technology were converted from analog to
digital to enable quantitative analysis. These observations are available at
http://lter.
