The purpose of this study is to measure the effectiveness of a wearable therapeutic ultrasound device for relief of pain associated with the trapezius muscle of the upper back over a 4-week period. The trapezius muscle is a wide, flat, superficial muscle that covers most of the upper back and the posterior of the neck.The hypothesis is that the ultrasound device will lower the reported daily pain level of subjects suffering from trapezius muscle pain in their upper back.