Page 102 - Zoo Animal Learning and Training

74 Box A2 ­o ouu ear hat u earr? earinng anduSound inuAnimals

VetBooks.ir 100 Threshold of hearing audiogram comparisons

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Threshold of hearing (dB) (re: 20 micro-Pa) 60

40

20

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–20
16 32 63 125 250 500 1000 2000 4000 8000 16000 32000 64000 128000
Octave band freuency (Hz)
Cat (Felis catus) Elephant Horse House Finch
Human Mice Yellow Baboon
Figure A2.1 An Illustration of several audiograms for different mammal species, illustrating their hearing threshold
(dB) and frequency (Hz). Source: created by Erik Miller‐Klein based on information available in Fay (1988).

described as speech intelligibility for human patrons, or nearby roadways. These potential
communication. This is the evaluation of the noisy distractions coupled with the mobile
sound level of the human’s voice (signal) pinna of most animals can make communi-
compared to the background noise level in cation more challenging for the trainer and
the training environment (noise); defined as difficult for the animal.
the signal‐to‐noise ratio. Research in class- Most healthy adult humans, which is
room environments has found that the mini- assumed to be the pool of zoo professionals,
mum signal‐to‐noise ratio must be 15 dB have trained their brains to be acutely aware
which means the sound from the zoo profes- of human speech patterns and effective at
sional’s voice must be at least 15 dB louder filtering out distracting noises. But most
than the other potentially distracting noises animals, much like juvenile humans, are still
in the animal’s environment (Klatte et al. learning the patterns of human speech and
2010). The average human speaks at a sound will have a much more difficult time under-
level of 65 dB at 1 m, and sound decays about standing instructions when there is compet-
3 dB per doubling of distance within an ing noise and stimuli. Consider evaluating
enclosed space and about 6 dB per doubling where you communicate with your animals,
of distance in an outdoor space. Based on and/or train them, with respect to noise
these average levels in an indoor environ- through the following simple experiment:
ment the zoo professional must be less than get two zoo professionals to stand the dis-
5 m from the animal for a space that is quiet tance expected for training exercises and
enough to hear your shoes land as you walk have one zoo professional wear a blindfold,
on a dry concrete floor, which would be a and have the other read a paragraph of a
background noise level of about 40 dB(A). newspaper or magazine. Could the blind-
Whereas with that same vocal level the folded zoo professional clearly understand
trainer would need to be no more than 3 m all of the words? Were there noises or
from the animal in an outdoor training sounds that were distracting? Consider
environment assuming there is no addi- evaluating your facilities through the ears of
tional background noise from air traffic, zoo your animals.