As a student, you might assume that your technical report's audience is your instructor, however, this may not always be the case. Your instructor may ask you to produce a report for your peers or for other engineers. However, you shouldn't always assume that your audience has a strong engineering background or is familiar with the engineering terminology you use. Always check with your instructor to know who your audience is.
As an engineer in the field, the most likely audience for the technical reports you produce is other engineers with a background similar to yours. This audience is more likely to understand the terminology you use. However, you should always evaluate who your readers will be before assuming they will understand your jargon. Consider how your readers will use your report. For instance, you might submit a technical report to a publication or your technical report may present a specific design. The audiences in each situation have different needs. Audiences may read the publication for information and insight while audiences reading about your specific design may critique your design or make decisions based on its content.