Features of reverberation time criteria application for sound classification in Lithuania

Abstract

Lithuanian sound classification scheme contains five sound classes and describes different acoustic quality of new, old and renovated buildings. Reverberation time is among descriptors used to express acoustic properties of different purpose building areas and building elements. In order to mitigate noise level in the rooms, the maximum permissible reverberation time values were set in octave bands at least in the frequency range 500–2000 Hz. The mandatory requirement was indicated for residential and some non-residential purpose buildings. Additionally expanded frequency range of estimation indicates more strict requirements and was dedicated for increasing clarity of speech and lowering tiredness in educational rooms. In case of teaching purpose rooms the lower limit of required reverberation starts from the 250 Hz octave band and in case of musical purpose rooms – from the 125 Hz. The experience obtained during more than 10 Years’ of practical labeling conformity with the corresponding acoustic class requirements for new and renovated buildings shows necessity to take into consideration the application of the sound absorbing treatments already in early design stage. Few typical cases of conducted reverberation time measurements in different purpose rooms are presented.