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Lecture room acoustic transformation in Poland

Mikolaj Jarosz, Concept Developer for educational premises in Poland speaks and demonstrates the dramatic acoustic difference in two similar lecture rooms. After the acoustic refurbishment of one of the lecture rooms at Krakow Technical University (PK) in Poland it is now possible to hear the difference as experienced by EDUnet and captured on a phone during a recent meeting there.

The two lecture rooms are identical in shape and are back to back in the building at the end of the corridor. Originally these 14 meters long and 3,7 m high halls were once a soldiers’ rooms, since whole building was constructed in 19th century as an army barracks. The untreated room is on the west side where the afternoon sun is coming in and the treated room (acoustic suspended ceiling and acoustic wall panels) is on the east side.
The acoustic treatment designed by dr Andrzej Kłosak from PK was followed by accurate measurements of room acoustic descriptors. Measured Speech Transmission Index (STI) values reflect listener’s subjective impression. STI range rose from 0,43 – 0,56 (depending on positions in the hall – with worst places at rear part) to 0,58 – 0,75. According to intelligibility rating in EN ISO 9921, intelligibility was shifted from “Poor” to “Fair” in rear part of the hall and from “Fair” to “Excellent” in front. Because its length, acoustically treated hall is still demanding from teacher operating natural voice but is considered by students as far better. The film actually indicates a change from unsatisfactory or poor to at least good which you can experience with the video. Also, rough subjective intelligibility test (CVC test) shows significant improvement from over 30% wrong answers to 14% (average for whole hall).
Reverberation Time (in empty but furnished hall) shows a considerable drop from 1,9 to 0,6 s (at 1 kHz) and from 1.4s to 0.5 s (at 125 Hz). STI measurements were done under 35 dBA background noise level.
Andrzej Kłosak said that students at the back of the room are noted to be much more attentive and pay attention throughout instead of having their own discussions at the back.
Click here to see and hear and the dramatic difference. For more info contact Mikolaj Jarosz.

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