Students talking in various small goups

What’s that stunning transparency based upon?

Psychoacoustics – cocktail party effect in this case.

Whom?

Cocktail party effect, discovered 1953, describes the ability of the human auditory system to focus its listening attention on a single talker, among a mixture of conversations and background noises, ignoring other conversations.

Cartoon illustrating a cocktail party
This is a cartoon illustrating the idea that at a cocktail party the brain activity synchronizes to that of an attended speaker, effectively putting them on the same wavelength
How pronounced is this effect?

Within such selective perception, the hearing reaches noise suppression from 9 to 15 dB, i.e., the acoustic source, on which humans concentrate, subjectively seems to be many times louder than ambient noise of the same level. This even holds if ambient noise is louder than the information by a similar amount (»negative S/N«). On the other hand, a microphone recording would capture mainly background noise, as any selective perception does not apply.

Brain with Single Talker / Cocktailparty Effect Activity Zones marked by Dots
Location of sites with significant LF phase-ITC (left) and HG power-ITC (right) in both conditions. The colors of the dots represent the ITC value at each site
How is this related to acoustic transparency of a room?

To come to the point: within a room, a related side-effect of the classical cocktail party effect results in greatly suppressed perception of spatiality - the subjective audible information sounds virtually dry, and with minimum reverberation.

A microphone positioned at the same location would capture blurred, slushy, and over-reverberating information instead. That very sound you know from bootleg recordings or YouTube live videos.

How is this related to practical application of room simulations models?

Various users have reported that during the progress of a mixing session, they are tempted to increase the wet signal over and over again. When returning from the cafeteria, they found their mix totally swamped with reverb. But after just about 30 seconds of listening, everything seemed to be ok again. Their advice: when mixing with QUANTEC, take regular short pauses, then return with “fresh ears” for a second opinion.

Once again, your ideas seem to be ahead of the pack …

That’s by no means my merit! – It was surprise to me too, that even within the scope of cocktail party effect, skillfully-designed room simulation models behave just like real rooms, i.e. they supply the human hearing system with all the essential clues.

If those essential clues are missing or incomplete, as it’s the case with most of my competitors’ reverberation devices and algorithms, the human auditory system reacts just like a microphone: the sound is unintelligible, slushy, and with far too much reverberation.


Related links
  • Cocktail party effect
    Wikipedia
  • Solving the Cocktail Party Problem -
    How we can focus on one speaker in noisy crowds?

    Cocktail party effect from neurologists’ point of view
    Science Daily

Picture Credits
  1. Sebastian Bernhard / pixelio.de (header image)
  2. Neuron, Zion-Golumbic et al.
  3. Figure 1C, Neuron, Zion-Golumbic et al.

One thought on “What’s that stunning transparency based upon?”

  1. With this article, I wanted to give you an idea about the basic cause of the acoustic transparency of my room-models.

    What I want to clearly emphasize once again is that asymmetrical relation: the room (or room model) sends out clues that enable the human ear and brain to remove distracting echoes.

    But asymmetry would conflict with the cocktail party cartoon model above, where the various parties get tuned or “zero in” on their respective group members. My advice to the neurologists: it’s enough to search for the secrets solely at the receiving end, as in fact it doesn’t really matter whether the clues originate from a dumb room or a dumb person.

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