A novel device for the calibration of sonic and ultrasonic recording transducers

•No devices currently exist to calibrate the amplification of vocalization recordings.•Calibration Unit for Recording Transducers (CURT) are designed to fill this need.•It emits a tunable frequency and amplitude in human-sonic and -ultrasonic ranges.•It is highly portable and fits a variety of microphone connector types.•We demonstrate the reliability of the unit and show the improvement in data quality. Recently, there has been an increase in the analysis of animal vocalizations in behavioral neuroscience as a social cue or indicator of neurological integrity. Despite the multitude of researchers examining vocalizations in a variety of species, no inexpensive, tunable devices currently exist to calibrate the amplification applied to such vocalizations before data are collected. Many commercially available recording systems have analog adjustments for gain, but such methods are notoriously unreliable and highly variable. Without a consistent level of gain, the amplitudes of recorded acoustic signals cannot be reliably compared. Here, we describe an apparatus designed to fulfill this need, which we have labeled the Calibration Unit for Recording Transducers (CURT). To maximize application to various fields, its emitted frequency and amplitude are tunable to output frequencies in both human-sonic (20Hz–20kHz) and human-ultrasonic ranges (20Hz–100kHz). Additionally, it is a portable (weighing approximately 180g), customizable, stand-alone unit, and fits a variety of microphone connector types. The CURT is also relatively low cost to build (under 250.00 USD), thereby making such a device available to as many researchers as possible in animal behavior and neuroscience.