Position the microphone in such a way that it receives sound optimally to minimize the effect of the position of the animal in the test environment. Here we report basic examples from the literature.
Test setups
Microphones are positioned suspended 2 to 20 cm above the cage, pointing downward. Testing cages are generally placed in a sound-attenuating chamber.
Separation test for rodent pups
Pups are placed into an empty container located inside a sound-attenuating chamber. The microphone is placed through a hole in the middle of the cover of the chamber, about 20 cm above the pup.
Position the microphone outside the chamber behind a mesh screen, if possible between the response levers at approximately head-level of the animal.
Male-female interaction (rats)
The test cage is divided in two compartments, the lower one for the male, and the upper one for the female. The microphone is attached to the divider, pointing to the lower compartment. Holes are drilled into the dividing panel to allow odor to pass to the male chamber. The diameter of the holes is smaller than the 50-kHz vocalization wavelength to sufficiently attenuate female vocalizations (Ciucci et al., Behav Brain Res. 182: 284–289, 2007)
In this setup, a male rat is paired with another male and housed throughout the experiment period. Each pair is housed in a polycarbonate cage (26 cm width x 43 cm depth x 20 cm height) in an environmentally controlled rearing system where temperature and humidity are kept constant and external sound and light sources are shut out. The microphones were suspended close to the lid of the cage (Takahashi et al., PLoS ONE 5(11): e14115, 2010. doi:10.1371/journal.pone.00141152010)
Eliciting vocalizations for test purposes
For optimal gain adjustment, it is important that animals produce vocalizations. To trigger vocalizations:
nFor mother-pup interaction: separate the pups.
nFor male-male interactions (mice): add bedding contaminated with urine of another male in the cage.
nFor male-female interactions (mice): Wild-derived male mice increase the number and diversity of courtship vocalizations if they previously interacted with a female (Zala et al 2020). The exposure to a female partner or to the urine induces a clear USV response in adult male mice with previous reproductive experience (Holy and Guo 2005, Maggio et al. 1983; Nyby 2001, Whitney and Nyby 1979).
nFor prairie voles: put two individuals in the cage (e.g. same-sex siblings). The frequency of vocalizations is reduced when the animals are placed in separate, side-by-side cages. For single-individual recordings, optimal distance is about 15 cm (6 in) (Stewart A.M. PhD thesis, University of Illinois at Chicago, 2012).
Relevant literature
Browse to
https://www.noldus.com/ultravox-xt/resources
then under Products click UltraVox.
Animal care guidelines
http://www.animalethics.org.au/policies-and-guidelines/animal-care