I am building a matlab simulation that applies room compensation to a 3D audio rendering system, and I'm searching for the frequency dependent sound absorption coefficients of various materials in order to extract the reflection coefficients.
However all the tables I found provide absorption coefficients for different octave frequency bands that have center frequency from 125Hz to 4kHz or at most 8kHz, but in my case I need to consider frequencies up to 20kHz.
My question is why are tables for sound absorption coefficients limited to such frequency range and how should I consider the coefficients for higher frequencies(i.e. higher than 10kHz) and also for lower ones(i.e. lower than 80 Hz)?
I found the tables in the annex section of the book "Auralization" by Dr. Michael Vorländer, which uses the ISO 354:2003 standard in order to perform the measurements.
The only resource where I found tables for frequency values higher than 8kHz was this paper: https://www.degruyter.com/downloadpdf/j/aoa.2013.38.issue-2/aoa-2013-0020/aoa-2013-0020.pdf where it is proposed an alternative method w.r.t. the previously mentioned standard in order to take the measurements from 50Hz to 50kHz, however these are provided just for very few materials.