The bubble chambers of the PICO collaboration use the acoustic signal generated from nucleations to classify nuclear recoil events from alpha decays in the bulk fluid. The success of these detectors in probing the potential WIMP-proton cross section comes in part from the low energy threshold that can be achieved. This nucleation threshold, based on the Seitz model, is dependent on fluid type, pressure, and temperature. At higher thresholds bubble nucleation does occur but with a significant loss in the measurable acoustic signal. To investigate this, the acoustic response of bulk nuclear recoil events was measured as a function of pressure and temperature and found to depend exponentially on both parameters. Understanding the form of the acoustic response can be used to predict potential operating conditions for specific thresholds in future larger-scale superheated liquid detectors. Details of the measurement in a small-scale test setup and a comparison to existing data will be presented.