This means that the slits absorb the sound energy on all intervals of the muffling of the sound field. The investigation showed that, with the slits present, the reverberation time values were reduced by 0.4–0.8 s throughout the interval when the muffling was approximated every 10 dB, starting from 0 to – 30 dB and from – 5 to – 35 dB. Then the reverberation times of a non-filtered signal must be different when the muffling is approximated every 10 dB. The muffling varies on differently in different time intervals. The muffling of the sound field of the model is not exponent in character. Given small slit dimensions and overall slit length, the change of 2–3 dB is quite significant. With the slits present, the muffling occurs faster and the greatest difference of 2–3 dB is observed in the interval of 1000–2500 ms. The experiments showed that the slits in the model influenced the muffling of the sound energy starting from 200 ms. A 2000 Hz upper limit was established to ensure that the Nyquist frequency exceeds 3. All frequencies were converted into real ones in the diagrams. The frequency of quantization of the signal was 166.6 kHz and the quantization time was 6 mcs. The frequencies examined fell in the range between 1250 Hz and 50000 Hz. The positions of both the source and the ¼ microphone coincided in all cases. The sound source was put through a hole in the floor in order to improve the directivity diagram of the radiation. A spark sound source was used for the radiation of signals within the required spectrum. Their overall length was about 10–12 m (converted to real values). There were 1 to 3 mm slits between the floor and the walls of the model. Thus, all materials employed in the model were similar to those of the real hall by their sound-absorption properties. The floor and the ceiling of the model were made of cloth-based laminate, while the walls of plywood 8 mm thick, with three layers of varnish. The hall is of rectangular form, 13.6 m in length, 10.7 m in width and 7 m in height. The Small Hall of the Lithuanian National Philharmonic Society was selected for the investigations. ![]() The influence of the slits between the walls and the floor of the model upon the objective acoustical indicators was examined in a scaled model of a hall.
0 Comments
Leave a Reply. |