Human hearing of frequencies is calculated on a scale of hertz or cycles per second.  The commonly defined range of human hearing is 20 hertz to 20,000 hertz per second.  A graphical EQ device, be it a hardware version or a software plug-in like those shown here generally work within that range. (Depending on your age and life experiences your hearing may be markedly less than this…)   In the application of boosting or cutting particular frequencies there are also a few controls which determine how the boost or cut will be applied.  The first is the particular frequency itself, the second is the amount of boost or cut, usually described in decibels, and third is the “Q” or width of the boost or cut.  If the horizontal line is flat, as shown here, then no EQ processing is happening.

10 band parametric EQ

Looking at the photo here you can see the controls just described.  This particular EQ is a 10 band EQ meaning that you can affect 10 different bands or frequencies at one time.

The graph indicates the frequency to be affected sorted with the low frequencies at the left of the graph to the high frequencies at the right.  Each ‘band’ has several controls – on/off, the type of “curve” to be applied, the gain or amount of the processing, the frequency where things are being applied, the Q of the processing and the overall input of the source and the output after processing.

Bell EQ curve

Here is a bell curve which looks sort of like a – bell.  This is a very common way to apply EQ to a particular frequency.  The Q is set to very wide so it is affecting a wide range of frequencies that are near the key frequency.  Applying EQ to satisfaction is to determine the central frequency to be affected, the size of the Q and the shape of the curve and the amount of gain that is being cut or boosted.

Shelf EQ curve

Here is a shelf curve that sort of looks like – yes – a shelf.  Different EQ makers apply this differently and this one makes a slight cut prior to the boost.  By the way these are pretty extreme boosts being made in these examples to more clearly show what is being discussed.  Often EQ will be applied at much lower boosts or cuts and at several different frequencies.  The idea with EQ is generally to do as little as possible to affect the desired change.  You can easily mangle the recorded audio to something unacceptable.

Low Pass and High Pass filters

This picture shows a different type of EQ – the curve at the left is called a “High pass” filter and the curve at the right is called a “Low pass” filter.  These filters will remove all of the frequencies at the cut off frequency.  So, in this example, the high pass filter removes all frequencies below 100 hertz and the low pass filter removes all frequencies above 10,000 hertz.  These are very useful filters for removing unwanted elements of recordings.

These “pass filters” are powerful tools for affecting the recorded audio being processed.  Here are a few examples that might shed light on their particular usage.  Let’s say that your boom man has trouble holding the pole and his fingers are creating small “boom” sounds during the recording.  Often these noises are very low in the frequency range and are difficult to hear without a sub-woofer.  A high pass filter may remove all of the noises without affecting the quality of the recording.  Or perhaps the tracks sound a bit “murky” so a slight presence boost at 2.5K or 3.5K may help “lift” the voice and a small cut at 300 – 400 may remove a bit of “boominess.”   If you look at the EQ that has a low and high pass filter applied you’ll see that it creates a “band” of frequencies that will pass through it.  The other name for this sort of setting is a “band-pass” EQ and these can useful in a number of ways.  Since band passes limit the frequency range of a recorded signal they are useful for many things. Many devices such a telephones have a “limited band-width” so you can mimic this bandwidth with a band pass filter. 

Notch at 1K

Let’s say you hear a steady noise in your recording that is present in the upper frequencies.  You may want to try a “notch filter” which can notch out the offending frequency.  Here several bands are tied together to really define the notch.  The idea here is to carve out only the offending frequency and try not to disturb anything else around it.  As you can see a graphical EQ is a very handy way of visualizing your sound.  Mix engineers will often “sweep” the notch along that horizontal range of frequencies until the frequency range to reduce or add is pinpointed.  Notches can be very useful in eliminating any type of steady state noise.  Steady is the key idea because if the noise or sound oscillates to other frequencies then the notch is no longer relevant since it is specific to only a narrow range of frequency.

EQ is an amazing tool with many useful applications.  However it is not a miracle device and it is most certainly not a noise reduction device.  It can indeed reduce noise but it is less successful at that than a dedicated noise reduction device is.  There are “broad band” noises such as air conditioners that cross many frequencies at one time.  They usually can not be notched or pass filtered out.  They will require some different processing, but if you need simple boosts or cuts or if you have tones that need to be minimized or emphasized in your recordings that are steady state, EQ will be the right tool to use.

This is merely a quick explanation of this wonderful, misunderstood and useful tool.  Experiment with EQ and learn how each of the controls affect the frequencies.  Learn how cutting and boosting achieves different effects and how specific frequencies affect specific sources.  Listen to the world at large and imagine if you had to use EQ to recreate the sounds you hear.  Walk by a stone building with music playing inside, loud but boomy and distant, what EQ curves might be applied to a standard music track to achieve a similar sound?  Listen to the world around you. This in time will guide you on how to use EQ to mimic the sounds in and of everyday life.  And then use those ideas to create the sounds you hear from this world – or others. Comment with thoughts, ideas or questions at will.

Simply put an OMF file is a digital container of all the audio files, edits, crossfades, pans and volume automation from your non-linear video editing platform.  It is a mighty handy tool compared to the old way of doing things. 

Here is a screenshot from Final Cut Pro.  You can see that there are eight tracks of audio, the top four of which are muted.

There is volume automation, panning information and a general temp mix in this edit timeline.  When we export the OMF from this timeline it will include tracks 5 – 8 only.  The OMF sees those muted tracks and leaves them out of the final export.  Most sound editors will want it all.  So I’d say unmute before the OMF creation.

Also a small FYI for those of you still using Final Cut 5 and below, the OMF is not a full spec OMF file.  It will not include volume automation, which if it’s feature length can create whole lot of extra work.  Not that you won’t re-mix from the ground up which is usually the case, but the temp mix can be a real time-saver for long projects.

I’ve also included a screenshot of the actual export of the OMF from the Final Cut Program.  Nothing fancy just a simple pull-down under File/Export – you can see – Audio to OMF.

You’ll get another dialog box after that which will give you a few options.  One is the handle length or the amount of audio that will be included on either side of any cut.  Handles are very important and contain loads of valuable information for a sound editor.  I generally ask for handles to be at lease five seconds if possible.  The default in FCP is 30 frames or one second.  Another option is to include volume automation and I would also add that functionality as well.  You can also choose to include crossfades which can be re-created by ProTools or the program that will be importing the OMF if they are not included.  There was a bug a while back in OMF exports that was related to crossfades.  This is no longer an issue.

What has just been detailed here is merely the mechanics of creating the OMF file.  As you can see it is a pretty simple and straightforward process.  Avid, FCP and other leading non-linear video editors offer some sort of OMF functionality and exporting them are all about the same process.  Make sure to mark an in and an out point create the accompanying movie file as well as the OMF from these same stop and start points.

Now that we have detailed the process of the OMF export what should be on the timeline in your non-linear video editor?  In my humble opinion, in a world of “less is more”, for audio post I would say that “more is more”.  If you have alt takes of lines, include them.  If you have roomtones include them.  Please.  Pretty please.

In fact I’m going to stop there.  Roomtones are a key component in audio post.  Period.  Notice the use of the word – key.  Not optional, not “if I can get to it”, not anything other than – key.  Not having roomtone is like writing without an eraser, a delete key or white-out.  Whoever digitizes the original camera tapes or dats will surely come across them.  Digitize them and stick them in a folder to give the sound editor or better yet as I advised cut them into your timeline and export them with the OMF.

I often ask the production recordist why they did not include roomtones and am generally told that they did indeed record them.  But somehow they never found their way to audio post.  So what happens to them?  They get lost in the shuffle with the mistaken assumption that they are not all that important.

In general picture editing gets a bit of time to complete their process.  Sometimes months and sometimes a year will be spent creating the final locked picture edit.  At the end of that they want the audio edited, mixed and output pronto.  So the best picture editors assemble their audio in a meaningful way to make the audio editors task simpler.  One thing that must be remembered is that all of that audio will be picked through, sorted, rearranged and cut to different tracks by the sound editor since it is their’s and the mixer’s job is to create a set of mix stems.  The editor had to create only one stem – a stereo temp mix.  And because of that many picture editors get lazy and just have their audio fall any where there is is room on an audio track.  This is fine for their temp mix but will not do to create a proper mix.  If Sound effects and music and dialog are all jumbled in the timeline – they will also be jumbled in the OMF.

Who cares?  “The audio guy will sort it all out ….”  The person who will care is the person who foots the bill.  Why?  Because they are going to be paying good money for studio time and an experienced sound professional to do basic housecleaning on the OMF.  It may sound minor but audio post deliveries are always tight and getting tighter and to waste a whole lot of time on things that have nothing to do with sound design and mixing is also a waste of the Producer’s money.  If you have a feature length project where the audio tracks were assembled willy-nilly it will take considerable time to sort out.    I have received OMF’s when opened reveal that the boom track and the lav track swap from take to take.  My job is to find “the best” sound and make that sound better.  If the boom sounds best then that means I have to audition and sort every single sound bite to determine whether it is the boom or the lav.  There may be thousands of these audio files in the timeline.  If the editor has diligently always put the boom on one track and the lav on another then he has cut my prep time considerably and I can concentrate on the task of making the movie sound even better.  Feel free to comment with questions since this is a huge topic that I’ve barely touched on.