There is an increasing amount of research on ultrasonic vocalizations in bats, nocturnal primates and of course small rodents. Especially the vocalizations of the latter group play an important role in (etho)pharmacological research. In pharmalogical screens, the ultrasonic vocalizations of rats and mice are used as therapeutic models for finding new anxiolytic drugs. For instance, it is assumed that rat pup vocalizations model separation anxiety which often proceeds panic disorder.

In principle, vocalizations can be analyzed in three different domains: time, frequency and amplitude. In pharmacological research the time domain is found to be most important. Neuroscientists wish to determine parameters like total time spent vocalizing and total number of calls, but also the interval between successive bouts and the interval between the calls of a single bout is of interest. However, analyzing ultrasonic vocalizations can be troublesome. To humans, these vocalizations are inaudible and a professional system with ultrasonic microphone, amplifier and recorder is too expensive for most research laboratories.

An alternative solution is UltraVox (Figure 1). The UltraVox system is an easy-to-use tool for the automatic monitoring of the temporal structure of ultrasonic vocalizations. The system combines a bat detector, audio filter and data acquisition software. First, the bat detector shifts the high-frequency sound to the audible range. This sound is then fed into the audio filter. If the amplitude of the sound exceeds a threshold value, a signal is forwarded from the audio filter box to the PC. The UltraVox software converts the signal to onset and offset times of the vocalizations. The software is currently available under DOS. A Windows version is under development, a prototype of which will demonstrated during the presentation.

Figure 1. The UltraVox system: Mini-3 bat detector and carrying case (right), audio filter (front left) and computer monitor (back left) displaying the UltraVox software.

Although UltraVox has primarily been designed to monitor vocalizations in the ultrasonic range, calls of any nature can be automatically detected. For instance, the monitoring of audible sounds merely requires the use of a standard microphone instead of a bat detector.