Hi all, thanks again for the answers, it really made it much clearer for me.
I'm reading through Gefald chapter on masking and thought some people might also be interested in understading masking further,
so I made a very simplistic summary of a few points.
Please tell me if anything I wrote is wrong :)
1. Low freq mask higher freq more than high freq mask low freq.
2. Low freq mask mostly the higher freq that are closest to them. ("..vicinity of the masker...")
- Practical potential use:
A. You have a rich range instrument like a piano or bass, and there is a resonance or some accumulation of energy somewhere in the mids.
High pass it bellow the problem area temporarily and you will be able to hear more clearly the problem.
B. You have a bass rich mix, or any mix for that matter, high pass it to around 100hz (NS10 style) to reveal problems in higher freq.
3. Obviously masking increases as the intensity of the masker is raised compares to the maskee (the signal being masked).
4. "Upward spread of masking"
Masking spread, changes depends on the relative intensity.
For example, a masker sound at 1000hz at 40 db and a maskee at 20 db - the spread of masking will be symmetrical at this level.
The spread will shift higher as the masker raises.
So the 1000hz masker at 100db will mask much more the higher freq with little change to lower freq.
(See diagram, low left square, Gelfand's book, page 188)
The higher the level of a sound -> ability to hear frequencies above it decreases..
Or specifically, When the bass volume raises -> ability to hear higher freq decreases.
As the bass masking reach is wide, (See next #5 - the lower the masker's freq the wider is it's reach of masking higher)
And the parts closest to it will suffer the most (#2), in a bass rich mix, the low mids will be the part you will hear the least and will be most illusive to your ears.
If your mix is bass rich, it becomes even more crucial to check it high passed.
(I wish I knew this sooner...)
5. The lower the freq of the Masker the more spread it have upward.
As you probably noticed, a resonance peak in the mids, have a masking spread quite close to it.
While low freq resonance will have much more reach upward in it's masking.
(this is shown in the same diagram, at Gelfand's book, page 188)
*Not sure I can post it here due to copyright material
6. When the maskee and the masker are close in frequencies they can create combination tones that produces beats and it might be hard to determine if the result is beats or masking.
7. "Critical bandwidth of the auditory filter",
When the maskee is at the center frequency of a white noise masker.
and the white noise is filtered using low pass and high pass, there is a certain width which making the resulting filter wider beyond it, will cease to increase masking.
(although it would make the white noise louder)
This is the limit of the critical bandwidth of the ear's filter.
8. "Off-frequency listening"
The "Critical bandwidth of the auditory filter" in the ear is not always "focused" or "listen" in the area of the filter center.
Interesting phenomena which might suggest a counter-intuitive technique to experiment with:
So lets say there is some masking happen around 400hz.
While the ear's auditory filter is centered around that frequency (on-signal band) it might be hard to hear what is masked, obviously.. :)
if we increase some frequency somewhere else nearby (flanking or off-frequency bands) maybe at ~450hz, shifting our ear filter bandwidth there,
we might be able to better hear what's going on at 400hz.
Or you want to judge and focus better in what is going on in an area of the mix,
increase some other frequency nearby...
shifting the ear filter center a bit might result in less masking in the original intended area of focus..
*Not sure this is true but i'm trying to interept it to practical advice.
9. This also relates to "comodulation masking release"
- "Comodulation masking release reveals that the auditory system is able to capitalize upon information provided across critical band filters,
although a cohesive model explaining CMR is not yet apparent.
One type of explanation suggests that the information provided by the off-signal band helps the subject
know when the troughs or “dips” occur in the modulating noise.
Listening for the signal during these dips would result in a lower threshold (less masking)..."
- "Notice that the masked threshold does not improve if the on-signal
and off-signal noise bands are not comodulated"
Which means that increasing off-frequency bands will reveal sounds (reduce masking) only if there is modulation in the sound, static sounds will not work the same..
10. Masking Overshoot
When two sounds, a maskee and masker are played together the masking is highest.
The more the maskee is delayed compared to the masker, the less masking is happening.
*This relates and explains something I really love and find very interesting,
that as music is played live, transient information is rarely played together at a similar resolution and accuracy like digital DAWs are playing, of course...
When we create music in a DAW placing everything exactly on the beat, it is rather unrealistic, and creates masking.
That's it for now, I'm just in the middle of the chapter and will do the experiments mentioned above...
I hope this may benefit you