Investigating the influence of seating area design and enclosure on the seat-dip effect using scale model measurements

Henna Tahvanainen,Jin-Yong Jeon,Tapio Lokki,Hyung-Suk Jang

doi:10.1051/aacus/2020016

Henna Tahvanainen, Jin-Yong Jeon + Show 2 more

Open Access

https://doi.org/10.1051/aacus/2020016

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Abstract

The low-frequency attenuation in the direct sound due to the concert hall seats, i.e., the seat-dip effect, is studied with the help of a scale model comprising an adjustable seating area and an enclosed box. More particularly, different seat underpass sizes and floor raking angles are studied, and the results are averaged over multiple source positions. With the measurements on the seating area only, the main seat-dip frequency is found to depend on the seat back rest height, and on the degree of obstruction of the seat underpass. The attenuation bandwidth is found to depend mainly on the floor raking. The differences become less clear when seating area is enclosed by concert hall walls and ceiling because the early reflections from the concert hall geometry compensate the low-frequency attenuation in the direct sound. In addition, the low frequencies below the main seat-dip frequency are found to increase in the presence of unobstructed seat underpasses, and such seats are recommended for the maximal bass response in a concert hall.

Highlights

Scale models serve as a great tool to study acoustical properties of complex geometries, in particular at low frequencies
The seat-dip effect (SDE) is typically analysed in a time window of 15–20 ms after the direct sound in order to minimise the influence of other reflections in the hall
Adding a concert hall around the seating area creates a more complicated series of reflections arriving at the receiver which lengthen the decay time of the signal

Summary

Introduction

Scale models serve as a great tool to study acoustical properties of complex geometries, in particular at low frequencies. One of the low-frequency phenomena that has been studied with the scale models is the seat-dip effect (SDE) in concert halls The SDE arises from the complex seating area geometry as a series of diffracted and reflected sound waves that interfere either destructively or constructively with the direct sound, causing attenuation at some frequencies and boosts at other frequencies, respectively. These diffractionreflection phenomena that explain the mechanism of the SDE were confirmed by Ishida [5, 9] by using a simplified parallel barrier scale model. The frequency of the maximum attenuation is influenced predominantly by the dimensions of the seats, such as height of the back rest and underpass below the seat [3, 10], as well as the angle of arrival of the direct sound [3,4,5]

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