Which term refers to the multiplication of the signal frequency specifically by three?

The term that specifically refers to the multiplication of the signal frequency by three is triplers. This term indicates a process where the original frequency is increased to three times its initial value. In signal processing, triplers are often used to generate specific frequencies that are multiples of a base frequency and can be critical in various applications, such as generating signals for communications or other electronic systems.

While other options like "doubler" or "multiplier" may also indicate frequency multiplication, they do not specify the factor by which the frequency is increased. Harmonics refer to frequency components that are integer multiples of a fundamental frequency but do not specifically denote multiplication by three alone. Therefore, triplers is the most precise term for frequency multiplication specifically by three.