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I mean I'm pretty new to sound engineering. Can somebody at least introduce me to what each bar on the equalizer of a music player stands for and how would they effect the quality and perception of music? What are highs, lows and mids? How can different genres of music like electronic/trance/rock/metal/jazz be identified on the basis of the shapes of their high-low-mids...Links are also very welcome..

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There are two approaches in which you can learn it.

First one: use your ears! Experiment with what happens when you tweak the EQ settings for various kinds of audio, e.g. voice recordings, full mixed music tracks or white noise. You will soon get a feeling about what the highs/mids/lows are and which frequencies are prominent in which instruments. As a rough overview

  • All bass instruments (including bass drums / timpani) feature, obviously, predominantly (but not exclusively!) low frequencies. They are usually the only instruments you strongly hear at below 100 Hz.
  • "Loud-sounding" instruments, e.g. brass, snare drums, electric guitars, also loud voices, have strong higher-mid frequencies.
  • Instruments that sound "light", "crisp" etc., like cymbals, small percussion, acoustic guitars, "clear" "open" voices... have lots of highs.

From this it's readily deduced that musical styles which strongly feature a particular class of instruments also tend to have emphasis the frequencies these instruments are focused on; for instance in rock music there is a lot of mid frequencies, bass-heavy grooves have a lot of lows and "unplugged" or pop songs in general get their characteristic sound from lots of highs. However you need to be careful with such statements: most music styles feature instruments from all these classes, and depending on the mix the overall frequency distribution may be quite unlike the expented one.

The other approach is the physical one. When talking of "mids/highs/lows", one is essentially referring to the Fourier transform of a signal. This is a mechanism by which you can decompose any sound (sound being a description of how air pressure behaves in time, namely how the air oscillates) into a sum of uniform basis oscillations, namely sine oscillations, which can be thought of as "pure frequencies". Low frequencies are wide, slow oscillations, which can naturally only occur in sufficiently big instruments; so all acoustic bass instruments are somewhat large-ish. High frequencies, i.e. fast and small oscillations, are more predominantly produced by small instruments, but also in big instruments provided the fast oscillations are not dampened by soft materials.

When you use an equalizer, you can imagine this happens: the incoming signal is first Fourier-transformed into this frequency space, there you then have a single "volume fader" for each frequency component, and at the output the signal is transformed back to a single time-space signal. (Most EQs are not actually implemented in this way, but it is possible.) Just, you can't precisely control every frequency on its own (there are far too many) with a graphic EQ, instead a whole range of frequencies will be bundled into a frequency band; that's what you control with those bars. Depending on the application you may need to cut or boost very narrow band very precisely, in this case you need either a graphic EQ with a great lot of bands (typically 31 in professional applications) or, even more precise and therefore often preferred in studios, parametric EQs which allow you to select exactly what range you frequencies you whish to manipulate.

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I would like just to leave this here. independentrecording.net/irn/resources/freqchart/… –  Johnny Bigoode Jan 25 '12 at 17:28

While I think that the answer provided by leftaroundabout is totally spot on and correct, I would like to add the following to simplify:

Think of the equalizer as set of filters. What are you filtering? The musical or sonic spectra, typically in the 20 Hz to 20 K Hz range (human hearing). Each filter addresses a select band of frequencies from this spectra.

A common break down of the audio spectra into bands: 30Hz (low bass), 100Hz (mid-bass), 1kHz (midrange), 10kHz (upper midrange) and 20kHz (treble or high-frequency).

Using light as an analogy: a light equalizer would be like taking a light source and running it through a prism then taking each color and boosting or reducing it as you like to create your own spectra.

For further reading, "What is the Difference Between a Graphic and a Parametric Equalizer?" http://stereos.about.com/od/introductiontostereos/a/equalizers.htm

More on EQ: http://productionadvice.co.uk/using-eq/

EQ tutorial from ProSonus: http://www.presonus.com/community/learn/musicians/eq-tutorial/

Hope this helps

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