What is an equalizer and what does it do?

Hardware equalizers are sound-system components that can selectively raise or lower the volume of a specified range of sound, from bass at the low end to treble at the high end.

Software EQs like those included with iTunes simulate the same effect and can include handy presets for optimizing playback.

umm…I get the specified range part but the rest is quite confusing..haha but I get the idea..it increases or decreases some parts of sound…I see…thank you

An EQ just ephasises specific frequencies. You can shape the tone of a sound by adjusting the highs, lows, or mids.

Try and think of sound as color. And say a song is a painting comprised of colors. With an EQ you can make certain colors stronger, and others weaker. Creating the desired look and feel of an image.

ummm I think I go the point and how to use it…thanks people

I think Spargett and PupnTaco did a fine job of explaining the concept, but may I add:

Equalizers are intended to correct the tonal balance in the music, by adjusting only certain bands of frequencies (low, mid, high, or Bass, Mid, Treble, etc.). These ranges can either be amplified (turned up) or attenuated (turned down) independently of each other, so as to “bring out” subtleties otherwise lost in the audio recording, or to reduce the tonal imperfections in the music or audio program.

A perfect example of this is in voice-only recordings (e.g. audiobooks), especially where there is a background hiss or hum under the voice; a Vocal Equalizer preset, such as the “Vocal Booster” found on an iPod, is intended to boost the fundamental or primary tones of the human voice (turning up the bands of frequencies where the human voice has the most presence), while at the same time, turning down bands above and below the human voice range (hiss, and hum, respectively). The net result is a “clarification” of the voice.

One key fact about consumer usage of EQs is that people often mistake them for being “enhancers” of an inferior audio system; that is, they use bass boost and other presets such as “Rock” or “Loudness” as a means to “juice up” a weak component system (for example, small speakers, or low amplification). I admit that I have a pair of fairly lo-fi earbuds that I use for my iPhone, and the only way to make them sound good is to employ an EQ preset on the iPod to reduce the overly-harsh treble response of those earbuds (very bright sound). Although this is the case in many consumer electronics systems with mismatched components, it’s really not the proper application / purpose for EQ. EQ is meant to correct the tone of audio material, not inferior equipment.

Last nugget of ‘wisdom’-I tell my audio students that whenever they go to test audio electronics at a store, always note whether or not the salesperson has set the device in question with an EQ preset; remember that, all things being “equal” (pun intended), a device with a null (flat) EQ setting should sound “great” out of the box, with no processing, if you play a good quality recording (audio pros call this a “reference recording”) through the device. I tell my students (this may be a west coast reference)-be leary of the “Radio Shack Smile” that sales people put on (their devices)-referring to the usage of EQ on a system to “juice up” an otherwise inferior component system.

Shout-outs to Marina for referring me to this post…

What? Me and understanding music are about as far apart as earth and the sun. I like the sounds I like and have no clue how it is made and enhanced.

An equalizer in a fight is much easier to describe! It is anything that gives you an advantage over your opponent.

@sndfreQ: thanks!! a very helpful response!!