The present disclosure relates to devices and methods for determining the density of insulation (e.g., in a cavity). For example, one aspect of the disclosure is a device that includes a probe, an actuator, a sensor, and a control system. The control system is configured to cause the actuator to oscillate the probe. The sensor is configured to generate a signal that represents the density of insulation. Another aspect of the disclosure relates to a method for determining the density of insulation. The method includes placing a probe into contact with the insulation, causing, via an actuator, the probe to oscillate while in contact with the insulation, and generating, via a sensor, a signal that represents the density of insulation.