diff --git a/README.md b/README.md
index 0802195..54e3c18 100644
--- a/README.md
+++ b/README.md
@@ -19,6 +19,16 @@ Our goal is to make LLMs easier to use for developers, turning complex AI capabi
 ### Pre-requisite
 
 - Python >= 3.9
+- Environment variable `OPENAI_API_KEY` or other LLM API keys, for more details, see [here](https://nerif-ai.com/docs/nerif-environment)
+- Set default model and embedding model with `NERIF_DEFAULT_LLM_MODEL` and `NERIF_DEFAULT_EMBEDDING_MODEL`, for more details, see [here](https://nerif-ai.com/docs/nerif-environment)
+
+Example:
+
+```bash
+export OPENAI_API_KEY=`your_api_key`
+export NERIF_DEFAULT_LLM_MODEL=gpt-4o
+export NERIF_DEFAULT_EMBEDDING_MODEL=text-embedding-3-small
+```
 
 ### Install
 
@@ -33,6 +43,7 @@ from nerif.core import nerif
 from nerif.model import SimpleChatModel
 
 model = SimpleChatModel()
+# Default model is `gpt-4o`
 
 # Use nerif judge "natural language statement"
 if nerif("the sky is blue"):
diff --git a/docs/setup_guide.md b/docs/setup_guide.md
deleted file mode 100644
index 579bec7..0000000
--- a/docs/setup_guide.md
+++ /dev/null
@@ -1,18 +0,0 @@
-# Guide for setting environment up for development
-
- - locate to the root directory
- - create a new python environment
-   - `python -m venv venv; ./venv/Scripts/activate`
- - run `pip install -e .` in command lines
- - If you want to setup the environment for api keys instead of manually put it every single time, set up the environmental variables with your open ai api keys
-   - in windows you could do `setx OPENAI_API_KEY sk-xxxxxxxxx`
-   - in macos/linux you could do `export OPENAI_API_KEY=sk-xxxxxxxxx`
-   - The same goes for open router `OPENROUTER_API_KEY`
- - to test if everything is working, do the following:
-   - go to interactive command lines in python `python`
-    ```
-    from nerif import SimpleChatAgent
-    agent = SimpleChatAgent()
-    agent.chat("Hello world!")
-    >> 'Hello! How can I assist you today?'
-    ```
\ No newline at end of file
diff --git a/nerif/model/__init__.py b/nerif/model/__init__.py
index c22fc31..6a8d367 100644
--- a/nerif/model/__init__.py
+++ b/nerif/model/__init__.py
@@ -1,3 +1,4 @@
+from .audio_model import AudioModel, SpeechModel
 from .model import LogitsChatModel, SimpleChatModel, SimpleEmbeddingModel, VisionModel
 
 __all__ = [
@@ -5,4 +6,6 @@
     "SimpleChatModel",
     "SimpleEmbeddingModel",
     "VisionModel",
+    "AudioModel",
+    "SpeechModel",
 ]
diff --git a/nerif/model/audio_model.py b/nerif/model/audio_model.py
new file mode 100644
index 0000000..bd235ed
--- /dev/null
+++ b/nerif/model/audio_model.py
@@ -0,0 +1,52 @@
+import base64
+from pathlib import Path
+from typing import Any, List, Optional
+
+from openai import OpenAI
+
+from ..utils import (
+    LOGGER,
+    NERIF_DEFAULT_LLM_MODEL,
+    OPENAI_MODEL,
+    MessageType,
+    NerifTokenCounter,
+    get_litellm_embedding,
+    get_litellm_response,
+    get_ollama_response,
+    get_sllm_response,
+    get_vllm_response,
+)
+
+
+class AudioModel:
+    """
+    A simple agent for audio tasks. (audio transcription, speech to text)
+    """
+
+    def __init__(self):
+        self.client = OpenAI()
+
+    def transcribe(self, file: Path):
+        with open(file, "rb") as audio_file:
+            transcription = self.client.audio.transcriptions.create(
+                model="whisper-1",
+                file=audio_file,
+            )
+        return transcription
+
+
+class SpeechModel:
+    """
+    A simple agent for speech tasks. (speech model, text to speech)
+    """
+
+    def __init__(self):
+        self.client = OpenAI()
+
+    def text_to_speech(self, text: str, voice: str = "alloy"):
+        response = self.client.audio.speech.create(
+            model="tts-1",
+            input=text,
+            voice=voice,
+        )
+        return response
diff --git a/nerif/utils/utils.py b/nerif/utils/utils.py
index 0cf8cfb..51efdd5 100644
--- a/nerif/utils/utils.py
+++ b/nerif/utils/utils.py
@@ -185,7 +185,13 @@ def get_litellm_response(
             "messages": messages,
         }
     else:
-        raise ValueError(f"Model {model} not supported")
+        # default method: use openai style
+        kargs = {
+            "model": model,
+            "messages": messages,
+            "api_key": api_key,
+            "base_url": base_url,
+        }
 
     kargs["stream"] = stream
     kargs["temperature"] = temperature