To find the frequency of the plane progressive wave given by the equation $$y = 2 \cos 2 \pi(330 \mathrm{t} - x) \mathrm{m}$$, we start by analyzing the general form of a wave equation.

The general form of a wave equation is:

where:

• $$A$$ is the amplitude of the wave.
• $$f$$ is the frequency of the wave.
• $$t$$ is the time variable.
• $$k$$ is the wave number, defined as $$\frac{2 \pi}{\lambda}$$ where $$\lambda$$ is the wavelength.
• $$x$$ is the spatial variable.
• $$\phi$$ is the phase constant.

By comparing the given wave equation with the general form, we have:

We observe that the term $$2 \pi(330t - x)$$ corresponds to $$2 \pi ft - kx$$ in the general form.

From this, it is clear that:

• $$2 \pi ft \rightarrow 2 \pi \cdot 330 t$$
• Therefore, $$f = 330$$ Hz

So, the frequency of the wave is 330 Hz.

Thus, the correct answer is:

Option C: 330 Hz