Praat

Once the ducks were recorded in the sound chamber, we analyzed their vocalizations via the use of Adobe Premiere Pro, Adobe Audition, and Praat. Adobe Premiere Pro is a video editing program that allowed us to stitch together videos and audio recordings from the anechoic chamber. We then used Adobe Audition, a digital audio workstation with a waveform editing view used to isolate each vocalization. We also used Praat (Boersma 2001 ), a phonetics software, in conjunction with Adobe Audition, as it gave us a different view of each vocalization so we could correctly characterize and name each call (see Lucas et al. 2015 ). Each vocalization that was clipped was named based on a pre-determined naming system. This naming system was created based on the following criteria: number of pulses (number of waves when looking at a wavelength), amplitude (how loud each sound is, measured in decibels, [dB]), frequency (rate of the vibration of the sound traveling through the air, measured in hertz [Hz]), and the shape of any frequency modulation (variation of the frequency within a portion of the vocalization).

Table 1 shows the types of stimuli used in this study. Participants were seated approximately 1.1 m in front of a computer screen in a dimly lit, soundproofed, and electrically shielded room. Following the procedure used by Gong et al. (2013) (link), four pure tone stimuli (1,000 Hz vs. 2,000 Hz; 55 dB vs. 59 dB) were created using Adobe Audition 3.0 and verified using Praat. Pure tones with a duration of 375 ms were binaurally presented via Sennheiser headphones. The sound pressure level was monitored through a digital sound level meter.