What does it mean to have a negative frequency?

Question

If say, you pull the amplitude of a specific frequency down in an EQ to a negative value , what exactly is the physical result? How does it work

Answer 1

That is not a negative frequency. And it is not a negative amplitude either, because it is relative amplitude in dB. Negative dB simply means less than 1 relative to the reference level, so the amplitude is reduced, but not negative.



Increasing by 10 dB means multiplying by 10, so decreasing by 10 dB means dividing by 10. 0 dB just means keep it the same (multiply by 1). Thus, going below zero will just reduce the amplitude.

Answer 2

No such thing. Frequency is just a ratio of the number of times something happens over some specified basis. As we cannot have negative happenings, we cannot have negative frequency.



That is not to say you can't have negative amplitude however. But frequency and amplitude are horses of different colors. Let's look at what I think your question ought to have been, "What does it mean to have negative amplitude"?



Suppose we have a sine wave a = A sin(wt) which oscillates around V = 0 volts. So the voltage v = V + A sin(wt). As you can see, when wt = 270 deg (3/4 cycle), v = 0 - A and the voltage where measured is a negative voltage v = - A and there's a negative amplitude relative to the V = 0 baseline.

Answer 3

The signal is made up of many components each with a different frequency.



The EQ mid-setting is is the unprocessed signal.



A positive EQ setting boosts the amplitude of components of the signal in the frequency range (e.g. boosts the amount of bass frequencies).



A negative EQ setting reduces the amplitude of components of the signal in the frequency range (e.g. reduces the amount of higher frequencies).



The EQ does not change the frequencies, it changes the amplitudes (amounts) of the different frequencies present.



(By the way, you can not have a negative frequency. It is meaningless.)

Answer 4

The phase is inverted (-180 degrees). But no equalizer I know of can actually pull that trick.