# Sinusoidal Wave Terminology

Suppose I have a sinusoidal signal of the form $x(t) = a\sin\left(2\pi b(t-c)\right) + d$. I understand $a$ is the amplitude, $b$ is the wave number, and $c$ is the phase shift. I know that the term $d$ shifts the entire signal vertically, but does it have a specific name in signal processing?

## 1 Answer

It is usually called DC offset or DC component. Since you use $t$ as a variable, which suggests "time", the quantity $b$ would normally be called frequency. Also note that $c$ is not the phase but a time offset. The phase $\phi$ is usually defined as in

$$x(t)=A\sin(2\pi ft+\phi)\tag{1}$$

Comparing (1) to your formula gives $\phi=-2\pi bc$.

• Ah yes! I keep forgetting that the terminology changes if the variable is time vs space, even though the form is equivalent mathematically. – Paul May 4 '15 at 16:53