Alternative measurement methods for speech level reduction of booths in field conditions
Jukka S. Keränen, Jarkko Hakala, Johann Laukka, Valtteri O. Hongisto · 2024
The sound level reduction of enclosures and partial enclosures (booths, pods, partially closed furniture ensembles) should be primarily tested in laboratory (reverberation room) according to ISO 23351-1.The singlenumber outcome is speech level reduction, DS,A.However, very large products cannot be tested in laboratory.In addition, field testing is needed when the declared product performances are verified, or prototype products are developed.Standardized field method does not exist.The purpose of this study is to compare methods reaching engineering grade of accuracy in field conditions.The apparent speech level reduction, D'S,A, is determined by measuring the sound power levels radiated by a constant sound source with (the sound source in the booth), and without the booth.The difference between these sound power levels determines the speech level reduction.The sound power levels can be measured according to ISO 3744, ISO 3747, or ISO 9614-2 with engineering grade of accuracy.We tested one booth in laboratory and in six different field conditions.The results are compared and discussed.Field results show acceptable agreement to laboratory results.This work is expected to help the development of ISO DIS 23351-2.