  Large Language Models (LLMs) have been applied in the speech domain, often
incurring a performance drop due to misaligned between speech and language
representations. To bridge this gap, we propose a joint speech and language
model (SLM) using a Speech2Text adapter, which maps speech into text token
embedding space without speech information loss. Additionally, using a
CTC-based blank-filtering, we can reduce the speech sequence length to that of
text. In speech MultiWoz dataset (DSTC11 challenge), SLM largely improves the
dialog state tracking (DST) performance (24.7% to 28.4% accuracy). Further to
address errors on rare entities, we augment SLM with a Speech2Entity retriever,
which uses speech to retrieve relevant entities, and then adds them to the
original SLM input as a prefix. With this retrieval-augmented SLM (ReSLM), the
DST performance jumps to 34.6% accuracy. Moreover, augmenting the ASR task with
the dialog understanding task improves the ASR performance from 9.4% to 8.5%
WER.
