Knowing Your Frequencies

[flemingmras]

A good sound engineer knows his frequencies by ear. Ask George about this one. His sound engineer from Jedi Mind Trip was sound checking George's mic one time, and I'm watching him and George is going(not in so many words but along these lines) "Test test...take out 1.25kHz...test test...add some 800Hz...test test"...and I'm like "FUCK that guy knows his shit!"

Well I'm here to explain a simple way to learn to recognize and pinpoint frequencies by ear.

The theoretical human hearing range is said to be 20Hz-20kHz. This is a frequency range of a full 11 octaves, starting from E0 and ending at E10.

Most pro grade house EQs are of the ISO standard 31-band 1/3 octave graphic type. This means that starting from the lowest fader, every 3 faders is one octave up from the fader you started from. So on a typical 31-band graphic, your first 4 bands are 20Hz, 25Hz, 31.5Hz, and 40Hz.

Rule #1: Everytime you double the frequency, the note increases in pitch by one octave.

Rule #2: Everytime you cut the frequency in half, the note decreases in pitch by one octave.

Starting with those first 4 bands, obviously due to the rules stated above, 20Hz and 40Hz are exactly one octave apart from each other. Now we have 2 faders in between these two frequencies. This gives us control of the low side and the high side of this octave range. Each octave on a 31 band graphic is set up in this way.

Starting at 440, A4(the note A in the 4th octave range), which on a guitar is the 5th fret on the high E string...go to the 7th fret D string and you're at 220Hz, which is A3. Hit the A string open and you're at an A2, which is 110Hz. You can see how as you went down one octave each time the frequency cut in half. Now go to the 17th fret and you have an A5, at 880Hz, which is double 440.

Now starting at the 100Hz fader, look in between each octave. In between the 100Hz fader and the 200Hz fader there are 2 faders, again giving you control of the low and the high side of the octave range. Same with in between 200Hz and 400Hz, 400Hz to 800Hz, so on and so forth.

Now if you were to look at the frequencies on a 31 band graphic, they aren't actually dead on certain notes. However, when you start with...let's say 125Hz, which is VERY VERY close to a C3, go up to the next fader and you're at 160, which is VERY close to an E3, 200Hz which is VERY close to a G3, and then to 250Hz(one octave up from 125Hz), which is VERY close to a C4. This progression continues right up the scale until you get to 16kHz, then 20kHz is supposed to be an E10(almost not even audible as an actual note by the human ear).

So starting actually with 31.5Hz on the graphic(most speaker systems can't reproduce much lower than this anyway, on top of the fact there's really no musical information below this frequency anyway), you have a C1. Starting with this fader, go up one fader and you're at E1, up another and you're at G1, and up another you're an octave up from where you started at C2. Starting at 31.5Hz, each fader goes E G C, E G C, E G C...so on and so forth until you hit 16kHz, then the 20kHz fader is an E10 which is not even audible to most people.

So start learning frequencies. Again that test CD download in the "Gain Structure" topic has all these frequencies. Here is the track listing for the frequencies. Some non-ISO frequencies are included, but I'll skip those track numbers and only list the ISO standard freqs.

Track 12: 20Hz E0
Track 13: 25Hz G0
Track 14: 31.5Hz C1
Track 15: 40Hz E1
Track 16: 50Hz G1
Track 18: 63Hz C2
Track 20: 80Hz E2
Track 22: 100Hz G2
Track 23: 125Hz C3
Track 24: 160Hz E3
Track 25: 200Hz G3
Track 26: 250Hz C4 Middle C(I call this pure tone "video game" C)
Track 27: 315Hz E4
Track 28: 400Hz G4
Track 29: 500Hz C5
Track 30: 630Hz E5
Track 31: 800Hz G5
Track 5: 1kHz C6
Track 32: 1.25kHz E6
Track 33: 1.6khz G6
Track 34: 2kHz C7
Track 35: 2.5kHz E7
Track 36: 3.15kHz G7
Track 37: 4kHz C8
Track 38: 5kHz E8
Track 39: 6.3kHz G8
Track 40: 8kHz C9
Track 41: 10kHz E9
Track 42: 12.5kHz G9
Track 43: 16kHz C10
Track 44: 20kHz E10

Also look at how every 10 faders are even multiples. 20Hz, 200Hz, 2kHz, 20kHz...same with 31.5Hz, 315Hz, 3.15kHz...so on and so forth.

This should give you a good start at learning your frequencies. Download the test CD and listen to these tracks...this will help to train your ear to recognize problem frequencies at the drop of a dime.

Jon

[5150loveeddie]

tabarnac

[tonejones]

I wish I could remember where I saw it......

There's a downloadable freeware program to help train for freqs.

It is a 31-band graphic display on your computer desktop, and it rings a frequency until you find the right one and pull it down with your cursor.

It then re-sets the sliders and rings another freq.

Great tool!!!!! Just wish I could remember where I found it.......