先存着,过几天来翻。
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Equalizers and Filters
Just a quick note on this involved topic! An equalizer lets you raise or lower your signal in certain frequency bands, i.e. you can increase the lower end (add bass), the middle band (add presence) or the upper band (increase brilliance). But (IMHO) that does not really work!
Why? First of all, most digital eqs are not really "selective" enough to influence the exact region you want to influence. They tend to be too "broad" and not "steep" enough to be really useful (waiting for hate mail!!).
Note: From our experience, it's especially dangerous to boost the treble range (above 1000Hz) of your recording with a broad equalizer. Especially when you use an older mp3 encoder, you will suffer from this decision, because it might add noise and other audible "artefacts" to the result based on this operation!
On the other hand, "digital filters" (a more sophisticated version of equalizers) are sometimes a blessing! This is especially the case when working though material that has been recorded live on a stage with all kinds of power and signal cables crossing each other, or if you record back home sitting next to your computer with your room or table light on. The point is that power (AC!) comes with a certain frequency: 60 Hz in the USA, 50 Hz in other parts of the planet. This is the low-pitched hum that's creeping up your recordings!
This is the graphical display of a 60/120 Hz "notch" filter that very selectively erases these frequencies (US settings!). Oh, why the 120Hz, too? Because any 60Hz signal also contains some 120Hz parts (the 8th or "octave"). Too hard to explain here, just believe it, ok?
It's always a good idea to carefully listen to your raw recording and spot those "power hums". If you detect some, use such a special filter to remove it (but don't forget to check the result with the best audio test devices available: Your ears!).
http://www.farland-music.com/audio/filtering.html