Make it obvious that the employee is going to need to hear the audio within the training material within the Phish Threat console.
Most of the training we provide customers is in video format and requires the employee to hear what's being said. However most employees will not necessarily have headphones at work to view and hear these training videos. Perhaps consider this when creating more training but also ensure sysadmins are aware the training will require the employee to hear the audio to complete the training. That way they can pick and choose which training is better suited. Some offices allow headphones some might not.