Equalization's Effect on Speech
​
A SouND Studio Creation
All sound is made up of waves at different frequencies. Frequency is another way of saying the pitch of a sound. So a child's voice or a flute have higher frequencies than a man's voice or a tuba.
One way of looking at and analyzing sound is by looking at a map of the frequencies. The most common format of this is shown below where the range of frequencies is shown on the x axis and the magnitude (aka amplitude or strength) of frequencies present is on the y axis. Any spikes in the graph correspond to frequencies that are very loud in the signal.
Another format that can be used called a spectrogram is shown below. It shows how the frequencies present in a recording change over time. Time is on the x axis, the range of frequencies is on the y axis, and the magnitude of each frequency is shown through the color. Hotter colors indicate a stronger signal.
.png)
Equalization works by boosting certain frequencies while suppressing others. Below is a comparison of two spectrograms of the Yanny/Laurel recording. The image on the left is with the low frequencies boosted to emphasis the Laurel sounds. The image on the right is with the high frequencies boosted to make Yanny more audible.
.png)
.png)
An equalizer uses filters that isolate a range of frequencies and then variable amplifiers that change how much each range is boosted. Each of the sliders on the front of the equalizer changes how much each range of frequencies is being amplified or attenuated by the amplifier.
You will notice that in the image above, the center frequency for each slider is shown above it. Additionally, you may notice that the frequencies get further apart the higher they get. This is because it is easier for the human ear to distinguish low frequencies from each other than it is high frequencies.