Air Absorption Error in Room Acoustical Modeling

Abstract

Most statistical and ray-tracing computer models take into account the absorption of sound by air when calculating the reverberation time. Extensive research by many scientist lead to the standardized calculation model for pure tone air absorption. The phenomenon was discovered from a room acoustical point of view by Sabine, while the further development of the calculation model took place in the fields of physics and environmental noise. As a result, several parameters and units are used for the same phenomenon. However, air absorption is calculated for pure tones, while room acoustics calculations are performed for frequency bands. Most computer models use the center frequency of the normalized frequency bands to calculate the air absorption by the pure tone method. Frequency band reverberation measurements under laboratory and practical conditions show that errors larger than the JND are made in calculating the air absorption by this 'center frequency method'. No literature is found that provides an accurate air absorption calculation for frequency bands.

Acoustic 1/10th Scale Model Test of Concert Hall in Taiwan

“…Even it had applied the general spectrumintegration method for wideband sounds analyzed by fractional-octave band filter (Annex D of ISO 9613-1 1993). This software used already the frequency bands method instead of the pure tone method for air absorption calculation, and the "Edge frequency" method 3 (lower frequency of the octave band instead of the central frequency) was also applied, However, there are still some other problems that can influence the S/N ratio and the accuracy of tested impulse responses. Since we are not capable to controlling or improving the software before our model test, we preferred to use the conventional method to reduce the excessive air absorption at very high frequencies in the 1/10 th scale model…”

An Active and Passive Controllable Smart Glass Based on an Eco‐Friendly Aqueous Solution

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