diff --git a/audio.py b/audio.py
new file mode 100644
index 0000000..5b64345
--- /dev/null
+++ b/audio.py
@@ -0,0 +1,46 @@
+import wave
+import threading
+import numpy as np
+
+
+class AudioRecorder:
+    def __init__(self, sample_rate: int = 16000):
+        self.sample_rate = sample_rate
+        self._buffer: list[np.ndarray] = []
+        self._stream = None
+        self.is_recording = False
+        self._lock = threading.Lock()
+
+    def _callback(self, indata, frames, time, status):
+        if self.is_recording:
+            with self._lock:
+                self._buffer.append(indata[:, 0].copy().astype(np.int16))
+
+    def start(self):
+        import sounddevice as sd
+        self._buffer = []
+        self.is_recording = True
+        self._stream = sd.InputStream(
+            samplerate=self.sample_rate,
+            channels=1,
+            dtype="int16",
+            callback=self._callback,
+        )
+        self._stream.start()
+
+    def stop(self):
+        self.is_recording = False
+        if self._stream:
+            self._stream.stop()
+            self._stream.close()
+            self._stream = None
+
+    def save_wav(self, path: str) -> str:
+        with self._lock:
+            data = np.concatenate(self._buffer) if self._buffer else np.zeros(0, dtype=np.int16)
+        with wave.open(path, "wb") as wf:
+            wf.setnchannels(1)
+            wf.setsampwidth(2)
+            wf.setframerate(self.sample_rate)
+            wf.writeframes(data.tobytes())
+        return path
diff --git a/tests/test_audio.py b/tests/test_audio.py
new file mode 100644
index 0000000..fef3f84
--- /dev/null
+++ b/tests/test_audio.py
@@ -0,0 +1,29 @@
+import numpy as np
+from unittest.mock import patch, MagicMock
+
+
+def test_recorder_starts_and_stops():
+    from audio import AudioRecorder
+    with patch("sounddevice.InputStream") as MockStream:
+        mock_stream = MagicMock()
+        MockStream.return_value.start = MagicMock()
+        MockStream.return_value.stop = MagicMock()
+        MockStream.return_value.close = MagicMock()
+        recorder = AudioRecorder(sample_rate=16000)
+        assert not recorder.is_recording
+        recorder._stream = MockStream.return_value
+        recorder.is_recording = True
+        recorder.stop()
+        assert not recorder.is_recording
+
+
+def test_recorder_save_wav(tmp_path):
+    import wave
+    from audio import AudioRecorder
+    recorder = AudioRecorder(sample_rate=16000)
+    recorder._buffer = [np.zeros(1600, dtype=np.int16)]
+    out = str(tmp_path / "test.wav")
+    recorder.save_wav(out)
+    with wave.open(out) as wf:
+        assert wf.getframerate() == 16000
+        assert wf.getnchannels() == 1