diff --git a/test/sox_io_backend/test_info.py b/test/sox_io_backend/test_info.py
index 2b28ae4814..da5207a7e5 100644
--- a/test/sox_io_backend/test_info.py
+++ b/test/sox_io_backend/test_info.py
@@ -33,9 +33,9 @@ def test_wav(self, dtype, sample_rate, num_channels):
         data = get_wav_data(dtype, num_channels, normalize=False, num_frames=duration * sample_rate)
         save_wav(path, data, sample_rate)
         info = sox_io_backend.info(path)
-        assert info.get_sample_rate() == sample_rate
-        assert info.get_num_frames() == sample_rate * duration
-        assert info.get_num_channels() == num_channels
+        assert info.sample_rate == sample_rate
+        assert info.num_frames == sample_rate * duration
+        assert info.num_channels == num_channels
 
     @parameterized.expand(list(itertools.product(
         ['float32', 'int32', 'int16', 'uint8'],
@@ -49,9 +49,9 @@ def test_wav_multiple_channels(self, dtype, sample_rate, num_channels):
         data = get_wav_data(dtype, num_channels, normalize=False, num_frames=duration * sample_rate)
         save_wav(path, data, sample_rate)
         info = sox_io_backend.info(path)
-        assert info.get_sample_rate() == sample_rate
-        assert info.get_num_frames() == sample_rate * duration
-        assert info.get_num_channels() == num_channels
+        assert info.sample_rate == sample_rate
+        assert info.num_frames == sample_rate * duration
+        assert info.num_channels == num_channels
 
     @parameterized.expand(list(itertools.product(
         [8000, 16000],
@@ -67,10 +67,10 @@ def test_mp3(self, sample_rate, num_channels, bit_rate):
             compression=bit_rate, duration=duration,
         )
         info = sox_io_backend.info(path)
-        assert info.get_sample_rate() == sample_rate
+        assert info.sample_rate == sample_rate
         # mp3 does not preserve the number of samples
-        # assert info.get_num_frames() == sample_rate * duration
-        assert info.get_num_channels() == num_channels
+        # assert info.num_frames == sample_rate * duration
+        assert info.num_channels == num_channels
 
     @parameterized.expand(list(itertools.product(
         [8000, 16000],
@@ -86,9 +86,9 @@ def test_flac(self, sample_rate, num_channels, compression_level):
             compression=compression_level, duration=duration,
         )
         info = sox_io_backend.info(path)
-        assert info.get_sample_rate() == sample_rate
-        assert info.get_num_frames() == sample_rate * duration
-        assert info.get_num_channels() == num_channels
+        assert info.sample_rate == sample_rate
+        assert info.num_frames == sample_rate * duration
+        assert info.num_channels == num_channels
 
     @parameterized.expand(list(itertools.product(
         [8000, 16000],
@@ -104,9 +104,9 @@ def test_vorbis(self, sample_rate, num_channels, quality_level):
             compression=quality_level, duration=duration,
         )
         info = sox_io_backend.info(path)
-        assert info.get_sample_rate() == sample_rate
-        assert info.get_num_frames() == sample_rate * duration
-        assert info.get_num_channels() == num_channels
+        assert info.sample_rate == sample_rate
+        assert info.num_frames == sample_rate * duration
+        assert info.num_channels == num_channels
 
 
 @skipIfNoExtension
@@ -120,6 +120,6 @@ def test_opus(self, bitrate, num_channels, compression_level):
         """`sox_io_backend.info` can check opus file correcty"""
         path = get_asset_path('io', f'{bitrate}_{compression_level}_{num_channels}ch.opus')
         info = sox_io_backend.info(path)
-        assert info.get_sample_rate() == 48000
-        assert info.get_num_frames() == 32768
-        assert info.get_num_channels() == num_channels
+        assert info.sample_rate == 48000
+        assert info.num_frames == 32768
+        assert info.num_channels == num_channels
diff --git a/test/sox_io_backend/test_torchscript.py b/test/sox_io_backend/test_torchscript.py
index 522c1319ce..9a30aab0d2 100644
--- a/test/sox_io_backend/test_torchscript.py
+++ b/test/sox_io_backend/test_torchscript.py
@@ -20,7 +20,7 @@
 )
 
 
-def py_info_func(filepath: str) -> torch.classes.torchaudio.SignalInfo:
+def py_info_func(filepath: str) -> torchaudio.backend.sox_io_backend.AudioMetaData:
     return torchaudio.info(filepath)
 
 
@@ -63,9 +63,9 @@ def test_info_wav(self, dtype, sample_rate, num_channels):
         py_info = py_info_func(audio_path)
         ts_info = ts_info_func(audio_path)
 
-        assert py_info.get_sample_rate() == ts_info.get_sample_rate()
-        assert py_info.get_num_frames() == ts_info.get_num_frames()
-        assert py_info.get_num_channels() == ts_info.get_num_channels()
+        assert py_info.sample_rate == ts_info.sample_rate
+        assert py_info.num_frames == ts_info.num_frames
+        assert py_info.num_channels == ts_info.num_channels
 
     @parameterized.expand(list(itertools.product(
         ['float32', 'int32', 'int16', 'uint8'],
diff --git a/torchaudio/backend/sox_io_backend.py b/torchaudio/backend/sox_io_backend.py
index 2fef97917f..ced7b38d4b 100644
--- a/torchaudio/backend/sox_io_backend.py
+++ b/torchaudio/backend/sox_io_backend.py
@@ -6,10 +6,18 @@
 )
 
 
+class AudioMetaData:
+    def __init__(self, sample_rate: int, num_frames: int, num_channels: int):
+        self.sample_rate = sample_rate
+        self.num_frames = num_frames
+        self.num_channels = num_channels
+
+
 @_mod_utils.requires_module('torchaudio._torchaudio')
-def info(filepath: str) -> torch.classes.torchaudio.SignalInfo:
+def info(filepath: str) -> AudioMetaData:
     """Get signal information of an audio file."""
-    return torch.ops.torchaudio.sox_io_get_info(filepath)
+    sinfo = torch.ops.torchaudio.sox_io_get_info(filepath)
+    return AudioMetaData(sinfo.get_sample_rate(), sinfo.get_num_frames(), sinfo.get_num_channels())
 
 
 @_mod_utils.requires_module('torchaudio._torchaudio')
diff --git a/torchaudio/csrc/register.cpp b/torchaudio/csrc/register.cpp
index 538c3f0ea0..1def910ac9 100644
--- a/torchaudio/csrc/register.cpp
+++ b/torchaudio/csrc/register.cpp
@@ -4,21 +4,10 @@
 #include <torchaudio/csrc/sox_effects.h>
 #include <torchaudio/csrc/sox_io.h>
 #include <torchaudio/csrc/sox_utils.h>
-#include <torchaudio/csrc/typedefs.h>
 
 namespace torchaudio {
 namespace {
 
-////////////////////////////////////////////////////////////////////////////////
-// typedefs.h
-////////////////////////////////////////////////////////////////////////////////
-static auto registerSignalInfo =
-    torch::class_<SignalInfo>("torchaudio", "SignalInfo")
-        .def(torch::init<int64_t, int64_t, int64_t>())
-        .def("get_sample_rate", &SignalInfo::getSampleRate)
-        .def("get_num_channels", &SignalInfo::getNumChannels)
-        .def("get_num_frames", &SignalInfo::getNumFrames);
-
 ////////////////////////////////////////////////////////////////////////////////
 // sox_utils.h
 ////////////////////////////////////////////////////////////////////////////////
@@ -32,6 +21,12 @@ static auto registerTensorSignal =
 ////////////////////////////////////////////////////////////////////////////////
 // sox_io.h
 ////////////////////////////////////////////////////////////////////////////////
+static auto registerSignalInfo =
+    torch::class_<sox_io::SignalInfo>("torchaudio", "SignalInfo")
+        .def("get_sample_rate", &sox_io::SignalInfo::getSampleRate)
+        .def("get_num_channels", &sox_io::SignalInfo::getNumChannels)
+        .def("get_num_frames", &sox_io::SignalInfo::getNumFrames);
+
 static auto registerGetInfo = torch::RegisterOperators().op(
     torch::RegisterOperators::options()
         .schema(
diff --git a/torchaudio/csrc/sox_effects.h b/torchaudio/csrc/sox_effects.h
index 6e4a26628f..14bdbbfabc 100644
--- a/torchaudio/csrc/sox_effects.h
+++ b/torchaudio/csrc/sox_effects.h
@@ -2,7 +2,6 @@
 #define TORCHAUDIO_SOX_EFFECTS_H
 
 #include <torch/script.h>
-#include <torchaudio/csrc/typedefs.h>
 
 namespace torchaudio {
 namespace sox_effects {
diff --git a/torchaudio/csrc/sox_io.cpp b/torchaudio/csrc/sox_io.cpp
index 1870dd8c9f..ec62a57ce6 100644
--- a/torchaudio/csrc/sox_io.cpp
+++ b/torchaudio/csrc/sox_io.cpp
@@ -8,7 +8,27 @@ using namespace torchaudio::sox_utils;
 namespace torchaudio {
 namespace sox_io {
 
-c10::intrusive_ptr<torchaudio::SignalInfo> get_info(const std::string& path) {
+SignalInfo::SignalInfo(
+    const int64_t sample_rate_,
+    const int64_t num_channels_,
+    const int64_t num_frames_)
+    : sample_rate(sample_rate_),
+      num_channels(num_channels_),
+      num_frames(num_frames_){};
+
+int64_t SignalInfo::getSampleRate() const {
+  return sample_rate;
+}
+
+int64_t SignalInfo::getNumChannels() const {
+  return num_channels;
+}
+
+int64_t SignalInfo::getNumFrames() const {
+  return num_frames;
+}
+
+c10::intrusive_ptr<SignalInfo> get_info(const std::string& path) {
   SoxFormat sf(sox_open_read(
       path.c_str(),
       /*signal=*/nullptr,
@@ -19,7 +39,7 @@ c10::intrusive_ptr<torchaudio::SignalInfo> get_info(const std::string& path) {
     throw std::runtime_error("Error opening audio file");
   }
 
-  return c10::make_intrusive<torchaudio::SignalInfo>(
+  return c10::make_intrusive<SignalInfo>(
       static_cast<int64_t>(sf->signal.rate),
       static_cast<int64_t>(sf->signal.channels),
       static_cast<int64_t>(sf->signal.length / sf->signal.channels));
diff --git a/torchaudio/csrc/sox_io.h b/torchaudio/csrc/sox_io.h
index 310687bb7d..6384f983be 100644
--- a/torchaudio/csrc/sox_io.h
+++ b/torchaudio/csrc/sox_io.h
@@ -3,12 +3,25 @@
 
 #include <torch/script.h>
 #include <torchaudio/csrc/sox_utils.h>
-#include <torchaudio/csrc/typedefs.h>
 
 namespace torchaudio {
 namespace sox_io {
 
-c10::intrusive_ptr<torchaudio::SignalInfo> get_info(const std::string& path);
+struct SignalInfo : torch::CustomClassHolder {
+  int64_t sample_rate;
+  int64_t num_channels;
+  int64_t num_frames;
+
+  SignalInfo(
+      const int64_t sample_rate_,
+      const int64_t num_channels_,
+      const int64_t num_frames_);
+  int64_t getSampleRate() const;
+  int64_t getNumChannels() const;
+  int64_t getNumFrames() const;
+};
+
+c10::intrusive_ptr<SignalInfo> get_info(const std::string& path);
 
 c10::intrusive_ptr<torchaudio::sox_utils::TensorSignal> load_audio_file(
     const std::string& path,
diff --git a/torchaudio/csrc/typedefs.cpp b/torchaudio/csrc/typedefs.cpp
deleted file mode 100644
index f4136cc918..0000000000
--- a/torchaudio/csrc/typedefs.cpp
+++ /dev/null
@@ -1,23 +0,0 @@
-#include <torchaudio/csrc/typedefs.h>
-
-namespace torchaudio {
-SignalInfo::SignalInfo(
-    const int64_t sample_rate_,
-    const int64_t num_channels_,
-    const int64_t num_frames_)
-    : sample_rate(sample_rate_),
-      num_channels(num_channels_),
-      num_frames(num_frames_){};
-
-int64_t SignalInfo::getSampleRate() const {
-  return sample_rate;
-}
-
-int64_t SignalInfo::getNumChannels() const {
-  return num_channels;
-}
-
-int64_t SignalInfo::getNumFrames() const {
-  return num_frames;
-}
-} // namespace torchaudio
diff --git a/torchaudio/csrc/typedefs.h b/torchaudio/csrc/typedefs.h
deleted file mode 100644
index ddd210e647..0000000000
--- a/torchaudio/csrc/typedefs.h
+++ /dev/null
@@ -1,23 +0,0 @@
-#ifndef TORCHAUDIO_TYPDEFS_H
-#define TORCHAUDIO_TYPDEFS_H
-
-#include <torch/script.h>
-
-namespace torchaudio {
-struct SignalInfo : torch::CustomClassHolder {
-  int64_t sample_rate;
-  int64_t num_channels;
-  int64_t num_frames;
-
-  SignalInfo(
-      const int64_t sample_rate_,
-      const int64_t num_channels_,
-      const int64_t num_frames_);
-  int64_t getSampleRate() const;
-  int64_t getNumChannels() const;
-  int64_t getNumFrames() const;
-};
-
-} // namespace torchaudio
-
-#endif
diff --git a/torchaudio/extension/extension.py b/torchaudio/extension/extension.py
index 4d8ac4dcba..b01ba13e39 100644
--- a/torchaudio/extension/extension.py
+++ b/torchaudio/extension/extension.py
@@ -12,38 +12,9 @@ def _init_extension():
         _init_script_module(ext)
     else:
         warnings.warn('torchaudio C++ extension is not available.')
-        _init_dummy_module()
 
 
 def _init_script_module(module):
     path = importlib.util.find_spec(module).origin
     torch.classes.load_library(path)
     torch.ops.load_library(path)
-
-
-def _init_dummy_module():
-    class SignalInfo:
-        """Data class for audio format information
-
-        Used when torchaudio C++ extension is not available for annotating
-        sox_io backend functions so that torchaudio is still importable
-        without extension.
-        This class has to implement the same interface as C++ equivalent.
-        """
-        def __init__(self, sample_rate: int, num_channels: int, num_frames: int):
-            self.sample_rate = sample_rate
-            self.num_channels = num_channels
-            self.num_frames = num_frames
-
-        def get_sample_rate(self):
-            return self.sample_rate
-
-        def get_num_channels(self):
-            return self.num_channels
-
-        def get_num_frames(self):
-            return self.num_frames
-
-    DummyModule = namedtuple('torchaudio', ['SignalInfo'])
-    module = DummyModule(SignalInfo)
-    setattr(torch.classes, 'torchaudio', module)