Psychoacoustics / Cocktail Party Effect

Some of you may recall I started a thread on room acoustics recently. Well, in the course of my readings on the subject, I stumbled upon a host of interesting material on psychoacoustics, auditory illusions, etc. I figure the topic deserves it's own thread. Posting key excerpts for those of you lazy to follow links.

Let's start this off with something called 'the cocktail party effect'. Here's how Wikipedia defines it:

The cocktail party effect is the phenomenon of being able to focus one's auditory attention on a particular stimulus while filtering out a range of other stimuli, much the same way that a partygoer can focus on a single conversation in a noisy room.[1][2] This effect is what allows most people to "tune into" a single voice and "tune out" all others. It may also describe a similar phenomenon that occurs when one may immediately detect words of importance originating from unattended stimuli, for instance hearing one's name in another conversation.
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The research on this phenomenon is still on going. One paper argues that we can focus our attention on a particular 'auditory object' in a complex scene, the same way we might with a complex image.

Reactions? How does this affect how you interpret impressions? What does it mean for when someone says, "there's this one part of this one track where I'm waiting to hear how X headphone renders X detail"?

Some other effects:

The precedence effect is the psychoacoustic tidbit that came up in relation to room acoustics. It's almost like a bit of room correction built into our brain.

"The "precedence effect" was described and named in 1949 by Wallach et all. [3] They showed that when two identical sounds are presented in close succession they will be heard as a single fused sound. In their experiments, fusion occurred when the lag between the two sounds was in the range 1 to 5 ms for clicks, and up to 40 ms for more complex sounds such as speech or piano music. When the lag was longer, the second sound was heard as an echo.

Additionally, Wallach et al. demonstrated that when successive sounds coming from sources at different locations were heard as fused, the apparent location of the perceived sound was dominated by the location of the sound that reached the ears first (i.e. the first-arriving wavefront). The second-arriving sound had only a very small (albeit measurable) effect on the perceived location of the fused sound. They designated this phenomenon as the precedence effect, and noted that it explains why sound localization is possible in the typical situation where sounds reverberate from walls, furniture and the like, thus providing multiple, successive stimuli. They also noted that the precedence effect is an important factor in the perception of stereophonic sound."
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The franssen effect is a crazy trick involving listeners not being able to localize sounds properly between two loudspeakers.

The left speaker suddenly begins to produce a sharp pure tone. The two speakers are complementary to each other: i.e., as one increases, the other decreases. The left one is decreased exponentially, and the right speaker becomes the main source of the sound. The interesting illusion achieved here is that the listener perceives the sound as only coming from the left speaker, although the right speaker has been on most of the time.​

On psychoacoustics and lossy compression:

The innovation of lossy audio compression was to use psychoacoustics to recognize that not all data in an audio stream can be perceived by the human auditory system. Most lossy compression reduces perceptual redundancy by first identifying perceptually irrelevant sounds, that is, sounds that are very hard to hear. Typical examples include high frequencies or sounds that occur at the same time as louder sounds. Those sounds are coded with decreased accuracy or not at all. Due to the nature of lossy algorithms, audio quality suffers when a file is decompressed and recompressed (digital generation loss). This makes lossy compression unsuitable for storing the intermediate results in professional audio engineering applications, such as sound editing and multitrack recording. However, they are very popular with end users (particularly MP3) as a megabyte can store about a minute's worth of music at adequate quality.​