Tips for Audio Mixing: EQ Space
Posted 05 March 2007 - 01:05 PM
This is one article in a series of articles entitled Tips for Audio Mixing found here at Guitar for Beginners and Beyond. Check out the initial lesson, Tips for Audio Mixing: Overview, which outlines all of the articles in the series.
When you've established some basic ideas about where you want your components in the stereo spectrum, then it's time to understand how to create and further redefine the space around each component. Each individual instrument or vocal needs to occupy its own space within the audio spectrum.
For example if the vocal equalization range includes the same lo-mid frequencies as a tom, the result could be mud. The same is true when different vocals compete against each other. Make a separate space for backing vocals as compared with the main vocal.
Respecting EQ Space is probably the most important aspect of mixing music. And so, let's take specific sub-topics and expand.
What is Audio?
Audio can be described as alternating current which is broadcast into the air. Although it is invisible to the naked eye, it can easily be represented on an oscilloscope to determine the frequency of the signal.
The oscilloscope is a device used in electronic engineering/repair to view different forms of electronic current. Audio is alternating current. The frequency of alternating current is measured as the total positive and negative voltage (how much or how high/low the signal alternates above and below the zero volt line) and at what speed in time the signal travels. One cycle is measured as a wave form beginning at the zero volt line at the left side of the monitor, then the signal line going above (or below) the zero line and then returning to the zero line in the middle of the monitor. To complete the cycle, this wave repeats from the middle of the monitor and in the opposite direction (either above or below the zero volt line) and then finally returns again to the zero line at the right side of the monitor.
Imagine a viewing the outline of a symmetrical mountain. At the right edge of the base of the mountain, imagine viewing the reflected image as if you were looking onto the lake at the base of the mountain. The number of cycles (or mountains) that cross the screen in one second is called the frequency of the signal. The more frequent the signal (the higher frequency of the waveforms across the screen), the higher the pitch of the audio.
What is the Audio Spectrum?
The audio spectrum, 20 Hz to 20,000 Hz (or cycles per second. Hz is short for Hertz, the name of the guy who discovered this stuff), is how the entire range of human hearing is described. The upper limit of the spectrum will vary dependent on age and gender. The upper limit of the average male is 16 kHz (k represents thousand, or is pronounced 'kilo') and the average female will be about 18 kHz.
You've heard (literally) of 60 cycle hum?? No doubt. Our household AC we use for power is sent to us at 60 Hz (in the US), and 60 cycle hum happens when there isn't proper shielding of audio cables. The 60 Hz signal leaks its way into a cable carrying audio signals (over the medium of the air, hence the term RF or Radio Frequency) and is then amplified and sent to the speakers of the audio system.
Noise can be considered as a random combination of unrelated frequencies that have no definite pitch, as opposed to a musical sound that has a definite pitch (fundamental frequency) and a combination of related frequencies (harmonics).
Often times you'll hear about Pink Noise, all the frequencies of the audio spectrum, 20 Hz to 20,000 Hz. A Pink Noise generator is used in testing and calibrating speaker systems, audio equipment and acoustically designed structures (control rooms, studios, auditoriums, etc.) Pink noise generators are a useful noise, but random noise (white noise) is oh, so random!
The spectrum is explored further in the article under the title Tips for Audio Mixing: Sub-ranges of the Audio Spectrum. Look at this page to see what types of sound are in certain frequency ranges.
The next article in the series is Tips for Audio Mixing: Volume Space.
Solid Walnut Music/ASCAP
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