The Unetstack handbook refers to Urick's classic book 'The Principles of Sound', pp 105-111, 3rd Ed for transmission loss. There are many causes for absorption described therein. What is accounted for when estimating the absorption in Unetstack?
Second question, how do interference/collisions work in the Basic Acoustic Model, is interference from other nodes treated as added noise or something in that direction?
Losses taken into account in BasicAcousticChannel model:
The BasicAcousticChannel model treats interference as noise and computes a SINR. The SINR is used to compute the detection probability and the BER for a BPSK modulation with Rician fading and a processing/coding gain. The parameters of the model (e.g. ricianK, pfa, processingGain, fastFading, noiseLevel, bandwidth, spreading, carrierFrequency, etc) control the details of the gain, fading, etc.