Restaurants, meeting rooms, sports complexes, covered swimming pools, school canteens, covered school playgrounds, exhibition stalls or railway station halls, etc. - in all these locales, people's discussions create a high sound level (75 to 95 dB(A)) and a relatively stable ambient noise, but which is often perceived as a hubbub. When this reaches a certain value, the people present have to raise their voices or even shout in order to continue to communicate because it is the intelligibility of spoken words which ensure they are properly understood. This intelligibility depends on the ratio between the signal (the spoken words) and the ambient noise (the hubbub).
However, the power of people's voices is limited and the people present end up speaking less, which stabilises the ambient noise.
Thus, under certain acoustic conditions and site occupation conditions, you reach a situation where the people present are responsible for the cause and are the victims of the effect. This escalation of the sound is called “the cocktail effect" and can be avoided by preventing the threshold at which it occurs from being reached.
Measurements characterising this change in the
sound levels depending on the locales and the people there (adults or children) have enabled to establish thresholds which should not be exceeded .
What background noises ?
The uncomfortable phenomenon known as the cocktail effect begins at a threshold which differs for adults and children, who often speak loudly or shout.
Thus, for locales such as restaurants or other places where people gather, in order to avoid this cocktail effect, it is desirable to avoid exceeding 72 dB(A). On the other hand, for locales for children, it is desirable to avoid exceeding 80 dB(A) because above and beyond that, there is a risk of the professionals who work there going deaf.
Acoustic treatment of an auditorium
Acoustical wall panels
Sound distribution generated by a quartet after acoustic
treatment 1 dB(A) per change of colour