So you say this “unpleasant feeling” or initial bodily reaction is “neurobiological suffering”? But any suffering is connected to vedana. Also Lal describes dukha vedana as a vedana felt via the physical body (via five physical senses).
Could it be correct this way?: a “normal” sound coming to the ear is neutral vipaka. But a strong sound is not only sensed by the ear but also by the body (kaya rupa). Bodily sensations can be directly sukha and dukha vedana. This is what even the Arahant feels (pain) and what you call “neurobiological suffering”. Thus a very loud sound can be felt as dukha vedana, but not as domanassa vedana.
The same line of reasoning would be valid for smelling an acid. The smell is neutral vipaka but the acid would immediately cause dukha vedana via kaya rupa (body).