¿What is the Cocktail Party effect?
The Cocktail Party effect is the ability human beings have to focus the attention in an acoustic stimulus of his interest in a noisy environment full of other acoustic stimulus. This ability allows to focus the attention in only one ignoring (not processing) the rest of them. A good example of this is when someone hears his/her name in other conversation and start processing the information of the other conversation which seconds ago the brain was ignoring.
In 1953 Colin Cherry, a British scientist, found a correlation between this phenomenon of information processing and the physical features as tone and spatial position. Recent studies show that brain (motivations, expectations,..) and sight (size, color,..) also play a role in these psychological processes.
Cocktail Party effect in Room Acoustics: Excessive Reverberation (eco)
Cocktail Party effect depends on the environment in which conversations take place. Closed venues without proper conditioning will have high reverberation (eco). This Eco increases undesirable acoustic stimulus which lead to comprehension problems.
Enjoy time with our beloved in a Coffe Shop, Restaurant or Bar would be impossible without this ability to select a conversation. In most of these places without acoustic conditioning, this effect becomes harder to perform due to the increase of noise of both source and room amplification. This unfortunately very common situation might damage a meal, coffe or a drink in good company due to the low acoustic comfort level.
Reverberation zone (also called Eco zone) is where the reflected sound level is higher that direct path sound while Direct Field zone is the one where direct path sound level is higher. These two zones define the Critical Distance (CD). If the venue is not properly conditioned (very common for venues with high volume), the reverberation time will be too high. In these venues the Reverberant sound field will predominate over the direct path sound level in most of the space. This will result in short Critical Distance (CD), so if the receiver walks away from the source will fall into Reverberation Zone where word intelligibility in not good.
Another common situation is that a poor acoustic environment is easy to turn into a worse one due to the progressive reduction of the Critical Distance. While sat in a table source and receiver are in the limit of the Critical distance, logical reaction is trying to increase the Direct Field zone by rising the sould level of the conversation. This will create more reverberation in their table and the rest of the tables, causing a reduction on the Critical Distance of them and the rest of the people in the venue.
A) Room with proper conditioning, the receiver are in direct field zone; B) Room without proper conditioning will result in short Critical Distance (CD) and the reciver will be out of direct field zone.
Consequences of this problem will be decrease in acoustic comfort, irritation of vocal strings, lose of focus, stress and head ache.
Acoustic Solutions: Absorption
In order to fix the problem caused by the environment in the Cocktail Party effect ability is necessary to ensure:
- Acoustic Comfort.
- Proper Word intelligibility.
- Correct reception sound levels in Broadcasting system spaces.
The acoustic measures should reduce the Reverberation Time (RT), lowering the Reverberant field increasing the direct path zone. Reverberation Time RT, is calculated the time that happens from a sound to decrease its SPL by 60dB. The necessary quantity of absorbent solutions can be obtained by the Sabine formula, knowing the size of the venue and the current reverberation time.
RT60 = Reverberation Time (s)
V = volume of the venue (m3)
A = Absorption Area (Sabines)
dBcover offers several phono absorbent solutions to decrease the reverberation time of poor conditioned venues:
dBcomfort HP 50 Acoustic absorbent open-cell panel, semiflexible, termostable, wáter-resistant. It has high absorption performance thanks to its tri-dimensional celular structure. Can be installed inside the cavity, inside perforated ceilings, over the wall and ceiling or in baffle configuration hanging from the ceiling: https://dbcover.com/pdf/dBcomfort_FR.pdf
dBcomfort desing SCURE Special Acosutic Absorbent periodic panel solution. It combines acoustic performance, aesthetics and Fire-resistance. This meta-material allows to correct in a simple and quick way, por conditioned environment https://dbcover.com/pdf/dBcomfort_SCURE_FR.pdf