Scientific Article

Correlation of room acoustic parameters and noise level in eating establishments

¹ STU Bratislava, Faculty of Civil Engineering, Radlinského 11, 81005 Bratislava, Slovakia
² KU Leuven, Laboratory of Acoustics, Soft Matter and Biophysics, Department of Physics and Astronomy, Celestijnenlaan 200D, B3001 Heverlee, Belgium
³ KU Leuven, Department of Architecture, Campus Brussel and Gent, Hoogstraat 51, 9000 Gent / Paleizenstraat 65, 1030 Brussel, Belgium

^* Corresponding author: zelem.lukas@gmail.com

Received: 14 July 2022
Accepted: 2 June 2023

Abstract

This article addresses the impact of the occupancy level, the average acoustic absorption and the so-called acoustic capacity of a space, which is proportional with the volume and inversely proportional with the reverberation time, on the behavior of talking people in an eating establishments. Four different settings were compared: two casual dining restaurants, a self-service student canteen and a small faculty club. The Lombard effect was observed in all cases. In a restaurant with an average amount of absorbing surface of 2.4 m² or more per person, the sound pressure level increased with more than 3 dB per doubling of the number of people. Results for the student canteen show that people started to communicate less when the number of people present was so high that the absorbing surface dropped under 1.5 m²/person (80 people). The level even stopped to increase with increasing occupancy from 150 people present and beyond, corresponding with 0.8 m² of absorbing surface per person. This is roughly consistent with an estimated value for the acoustic capacity of that space, which was 189 people (corresponding with a table occupancy of about 72%). In the latter circumstances, the background noise level, as expressed by L_A,95 was as high as 69 dB. Overcoming this level for oral communication would require a not sustainable vocal effort. In the tests performed in other restaurants, the observed occupancy was below 60%, which, thanks to the higher number of absorbing surfaces in those restaurants, was well below the acoustic capacity.