There are 在 least three types of models out there: 1. 听觉模型s, 2. 发动机 models, and 3. 感觉运动模型s.
This is closest to my view. The access route from sound input to the conceptual system does not flow through the 发动机 system although the 发动机 system can modulate activity in the sensory system.
这是一个卡通 发动机 theory:
Something like this has been promoted by 自由人 in the form of the 言语感知运动理论, as well as by Fadiga. One comment I'm getting a lot lately (including from Luciano) is that no one really believes in the 发动机 theory. So here's a quote from the Fadiga & Craighero, 皮质，（2006）42，486-490：
According to 自由人’s theory … the listener understands the speaker when his/her articulatory 手势s representations are activated by the listening to verbal sounds. p. 487
自由人’s intuition … that the ultimate constituents of speech are not sounds but articulatory 手势s that have evolved exclusively 在 the service of language, seems to us a good way to consider speech processing in the more general context of action recognition. p. 489
On this view, the route from acoustic speech input to the conceptual system flows through the 发动机 system.
This seems to be what Fadiga has in mind based on his comments on this blog, namely that it is in the "matching" of the sensory and 发动机 systems that is critical for recognition to happen.
A 布拉德·布斯鲍姆（Brad Buchsbaum） pointed out, both a 发动机 theory and a sensory-motor theory would predict that damage to the 发动机-speech system should produce substantial deficits in speech recognition. As this prediction doesn't hold up empirically, these theories in their strong forms are wrong.