[macrae11]

JohnM wrote:

Hello Andrew,

Your understanding of that is incorrect, and attempting to extrapolate that to a simple frequency dependence magnifies the misunderstanding. Perception of sound is not an instantaneous process, it is affected by what is presented to the ear over a period. A demonstration of that is Temporal Masking, in which a loud sound can prevent us perceiving sounds that arrive up to 100ms after it (not surprising) but also sounds that arrived up to 20ms before it. That does not mean that we simply delay everything to see what might come next, but that our perception of what arrives is affected by all the arrivals within a time window. There is no perceived delay.

John, I understand that sound perception is not instantaneous. But in your initial post speaking of gate time, implied that temporal masking was frequency dependent. eg

JohnM wrote:

When you couple that with the effective gate time of the ear at such frequencies, 50ms or so,

This statement you made, seems to me like you are saying that there is different times for the brain to process signal depending on the frequency. This would cause a delay relative to higher frequencies.

JohnM wrote:

Meanwhile to return to the original question as to whether applying a filter to the direct sound at a low frequency means what we hear sounds correct or not, let's consider a very simple case of a 40Hz tone arriving at the ear accompanied by a single reflection from a wall a few feet away. For convenience let's have a path difference that corresponds to a quarter wave, 6.25ms, and allow the reflection to be as large as the direct signal. The signals arriving at the ear are then the direct sound from the speaker and a quarter wavelength delayed version. The sum of these two, using basic trig identities for sums of sines, is a sine wave at the original frequency with a 1/8th wavelength phase shift and an amplitude of sqrt(2) times the original, so as far as the listener is concerned the tone has been made louder. To get the tone to the level it would have had without the effect of the reflection we need to reduce the level of the original sound by 1/sqrt(2). In doing that the 1/8th wavelength phase shift remains, but the level is corrected and the listener is none the wiser.

Well the first reflection wouldn't be the same amplitude as the direct signal.(or at least if it is the listener has more acoustic issues than a little EQ could ever fix!) The issue here again I don't think is just about amplitude, it's about time.

JohnM wrote:

In the more general case of an enclosed space there are only specific frequencies, the modal resonances, at which the multiple reflections from the room's surfaces generate a stable standing wave. The effect at those frequencies is to alter the perceived level of those tones according to the amplitude of the standing wave at a given location in the room. Altering the level of the original sound correspondingly gets us back to the level a tone would have had without the room's influence, with the proviso that nothing can be done for locations where the amplitude of the standing wave is zero and more generally it is inadvisable to boost the signal in locations where the standing wave amplitude is lower than the original signal.

Here's the real issue(at least the one I've been talking about) modal resonances causing standing waves. Not only do these standing waves cause amplitude differences(which could be fixed with an EQ) but they also cause time differences. Notes ring out differently than they would without the influence of the room, lasting longer than they are supposed to. I don't think EQ can fix this. EQ will only lower the starting point of the frequency fundamental, which will cause it to dip into the noise floor sooner. Thus giving a perceived "correct" duration to the note, but not actually fixing the problem.