| dc.description.abstract | Objectives: Vocalizations of interest of newly weaned piglets were induced in order to assess
the performance of a new acoustic camera, that uses an array of 64 microphones to map sound
intensity over video recordings in the form of a heat map. The aim was to determine whether
the acoustic camera would be capable of detecting changes in vocalizations of newly weaned
piglets, which are related to their affective state. The assessment was performed by (1)
determining the types of background noise picked up by the acoustic camera; (2) assessing the
sensitivity of vocalization localization for grunts, barks and screams/squeals and (3)
determining the minimum distance between two piglets in order for the acoustic camera to
localize grunts, screams/squeals and simultaneous vocalizations correctly.
Materials and methods: For the first two objectives, six piglets were given free access to a
corridor, above which the acoustic camera was mounted in order to record sound. Vocalizations
for the third objective were recorded during the isolation of two piglets in the corridor. The
occurrence of grunts, barks, screams/squeals and simultaneous vocalizations were measured.
Results: The results of the first research aim showed that the acoustic camera picked up a lot
of background noise. Of all collected sound events occurring at a piglet’s snout, the proportions
of sound attributed to the smacking (0.50) and movement (0.41) of the piglets were especially
high. The results of the second research aim showed that the order from highest to lowest
proportions of correctly localized vocalizations were as following: barks (0.72),
screams/squeals (0.67) and grunts (0.19). The proportion of correctly localized barks was
significantly higher than the proportion of correctly localized grunts. And lastly, the results of
the third research aim showed that grunts produced by an individual piglet could be localized
most accurately at a distance of 40 cm and beyond. Screams/squeals produced by one piglet
could be localized most accurately at a distance of 20 cm and beyond. The correct localization
of simultaneous vocalizations turned out to improve as the distance between the piglets
increased. Due to the small sample size and various other limitations of this study, the results
should not be generalized to vocalizations of the entire population of newly weaned piglets.
Applicability: Some results indicate that the acoustic camera would be ready to detect changes
in a piglet’s affective state by measuring vocalizations. Such as the fact that the camera was
fairly good at correctly localizing barks and screams/squeals when there were six piglets in the
corridor. The acoustic camera was also able to correctly localize grunts and screams/squeals
from a distance of ≥40 and ≥20 cm respectively when there were two piglets in the corridor.
Despite these advantages, several improvements are needed before the acoustic camera would
be ready for use in commercial farms. First of all, the acoustic camera should be able to filter
out more background noise, especially the smacking and movement of the piglets. For a welfare
assessment based upon vocalizations, it is also necessary for the acoustic camera to become
better at localizing grunts. Future research is necessary, and should focus, among other things,
on the vocalization localization of larger groups of newly weaned piglets housed under different
conditions, and being able to differentiate between positive and negative vocalizations using
the acoustic camera. | |
