He often seems to be transmitting on a different frequency.

You are actually inside a living being, on a completely different frequency.

The man behind the counter seemed to be speaking on a different frequency.

It has at least one frequency, and usually many different frequencies.

In general, signals can be described as including a whole range of different frequencies added together.

It does this by breaking the sound or picture into different frequencies.

Just like with sound, you can make any picture out of different frequencies.

She says all sound is just different frequencies of the same thing.

Were they working on a different frequency, hidden in another dimension, what?

They may also have a different fundamental frequency, or other properties.