Originally Posted by markus767
I believe this is also a fundamental issue in hearing. Unfortunately virtually no research is available in that area. Toole talks vaguely about "adaption" but that's it.
Catching up on some older posts
. Dealing with the easy part, Dr. Toole dedicates an entire chapter (11) to Adaptation in his book. So not sure what is meant by "vaguely" dealing with it. In person, this is one of the top points he makes. Adaptation is as real as air and water when it comes to perception of sound. If I stop typing and listen, I all of a sudden hear the TV that is playing the morning news. Until that point, I had completely tuned it out even though it is playing at normal listening level. If I pause the TV and do the experiment again, all of a sudden I hear the faint hum of the fridge in the kitchen, the sound of birds chirping outside, etc. Try it. Stop reading this text and listen. Likely you will hear sounds that you were not aware of as you were focused on this text. Think of how fast the hum of the projector fan disappears when you start watching the movie.
Follow your loved ones from room to room. I bet their voice mostly or entirely sound the same even though the room reflections and hence, any measured frequency response or ETC would very a lot. Even if you hear a difference at first, it disappears over time.
This is one of the most fundamental principals in human auditory perception. That we have two mechanisms here: the ear hears the sound but the brain post-processes it. It is that post-processing that attempts to optimize what we hear. It does away with what it thinks is not useful and focuses on what is. Here is a nice experiment by Siegfried Linkwitz in his Audio Engineering Society Paper, Room Reflections Misunderstood?
:"It should also be noted in this experiment that when you listen to a CD with well-defined phantom images and sound stage between the two loudspeakers and then turn your head slowly clockwise, the phantom images and sound stage stay firmly centered between the loudspeakers. Even the sound timbre remains unchanged, just as with real sources and space. The frequency responses for left and right ear, though, change drastically with the rotation, as do the microphone signals. This is an example of the processing power of the ear-brain cognitive system, which compensates for the head movement. Playback of the in-room recording, however, shifts the phantom images to the left loudspeaker and collapses the soundstage."
Notice the contrast between what the ear hears up to the last sentence above, and what a microphone will record the response in the room and then played back. The former completely compensated and tuned out differences in frequency response and timing whereas the microphone recording could not as it has no "cognitive" ability like your ears has.
Why we have this ability is thought to be due to us adapting to our surroundings. Here is Linkwitz again:"In the evolution of natural hearing forest and savanna were the spaces for survival. To detect the proximity and direction of sound sources was essential for recognizing the largest threat. Forests are highly reverberant, the savanna is acoustically dead by comparison. Hearing evolved by learning how these environments change sounds. To recover the direct sound from a mixture of sounds, and therefore to know the true direction and distance of a potential thread, helped to survive. Savanna and forest provided an acoustic background. It could be ignored as long as there was no change from familiar sound patterns. A listening room is the modern equivalent to forest and savanna. We still use the now hardwired portions of the hearing process but adapt them to the new situation. We still can ignore the static background, in this case the room and the fixed loudspeakers, and automatically focus our attention on the direct sound, even when it creates an illusion."
I think everyone will attest to the truthfulness of what I have highlighted. We can draw immense enjoyment out of our systems even though they are in "untreated" rooms and have response anomalies that show ugliness in measurements but in reality may not contribute at all to our perception in the way we intuit. More examples of the difference between measurements and perceptions are in an article I wrote on this topic: Perception Effects of Room Reflections http://www.madronadigital.com/Library/RoomReflections.html
Linkwitz goes on to say:"It is very difficult to predict the subtleties of what is perceived by a listener from analyzing in-room steady-state frequency response or reflection measurements. The response graphs are difficult to interpret and can be misleading."
This is absolutely critical. Above the "transition frequency" of a few hundred hertz, what we measure, is not what we hear (again, see my article). It isn't the case in either frequency or time domain. While there is somewhat a work around reflected in Jerry's guide for frequency response (using different filtering), the measurements we use here don't remotely record what is being heard by two ears and a brain. They record what a microphone captures which does not at all match the responses of either components.
Fortunately, below the transition frequencies, i.e. the bass region, these effects essentially vanish. The wavelengths of sound become very large and dwarf the distance between the two ears. And our face and body no longer cast "acoustic shadows" so the differential between what each ear hears goes away. This is why if you want to do something to your room, the safest place is to optimize the bass. What you see in simple frequency response measurements is what you hear. Have a 10 dB peak? You will hear that and the improvement when you take that down. See a spike in ETC that is at Khz frequencies? Better watch out for a ton of things before acting on that.
And oh, don't let people shame you into "treating" you room. If you have well designed speakers, in typical furnished rooms, you may already have all the" treatments" you need. Here is Linkwitz again:"Two-channel playback in a normal living space can provide an experience that is fully satisfying as loudspeakers and room disappear and the illusion of being transported to a different place and moment in time takes over."
The trick as he and many other experts will say is to have a well designed speaker that produces similar response off-axis (sideways) than it does on-axis (directly coming at you). If you have that then the reflections will blend in like that forest analogy and you will have an enjoyable experience.
Net, net, adaptation is real and core part of our hearing system. It is that and many principals like it that lead us away from cookbook formulas that were designed years ago based on intuition of the ear working like a meter. And what we would picture the sound working as, in sharp contrast to what it really does.