Help needed with using Absorption Coefficient calculations from ISO354-Acoustics Forum-Acoustic Fields Forum

Hello!!

As part of my bachelor´s graduation project, I´m experimenting with a new material to determine it’s accoustics properties following the ISO3382-2 and ISO354 guidelines. But I´d like to get guidance on the resolution of this formula:

m = α/10lg(e)

Where α is appointed as an “attenuation coefficient” value from ISO9613, though im not sure if I should use the values listed on Table 1 on this standard or if I should calculate using the formuale listed. I’m using 1/3 Octave Band frequencies.

My doubt comes mainly because these are called as Decibel per Kilometer attenuation and ISO354 mentiones values are “Reciprocal Meters” and also because if i use the values from ISO9613, i get results below 0 and above 1 which seem to be quite out of the expectation.

Any guidance on this or, moreover, any guidance with interpreting Secion 8 of ISO354 will be highly appreciated.

Warm Regards,

Rod Herrera