diff --git a/egs/librispeech/ASR/pruned_transducer_stateless6/aug.py b/egs/librispeech/ASR/pruned_transducer_stateless6/aug.py
new file mode 100644
index 0000000000..0746d0036a
--- /dev/null
+++ b/egs/librispeech/ASR/pruned_transducer_stateless6/aug.py
@@ -0,0 +1,287 @@
+import math
+import random
+from typing import Dict, Optional, Tuple
+
+import numpy as np
+import torch
+
+
+class SpecAugment(torch.nn.Module):
+    """
+    SpecAugment performs three augmentations:
+    - time warping of the feature matrix
+    - masking of ranges of features (frequency bands)
+    - masking of ranges of frames (time)
+
+    The current implementation works with batches, but processes each example separately
+    in a loop rather than simultaneously to achieve different augmentation parameters for
+    each example.
+    """
+
+    def __init__(
+        self,
+        time_warp_factor: Optional[int] = 80,
+        num_feature_masks: int = 2,
+        features_mask_size: int = 27,
+        num_frame_masks: int = 10,
+        frames_mask_size: int = 100,
+        max_frames_mask_fraction: float = 0.15,
+        p=0.9,
+    ):
+        """
+        SpecAugment's constructor.
+
+        :param time_warp_factor: parameter for the time warping; larger values mean more warping.
+            Set to ``None``, or less than ``1``, to disable.
+        :param num_feature_masks: how many feature masks should be applied. Set to ``0`` to disable.
+        :param features_mask_size: the width of the feature mask (expressed in the number of masked feature bins).
+            This is the ``F`` parameter from the SpecAugment paper.
+        :param num_frame_masks: the number of masking regions for utterances. Set to ``0`` to disable.
+        :param frames_mask_size: the width of the frame (temporal) masks (expressed in the number of masked frames).
+            This is the ``T`` parameter from the SpecAugment paper.
+        :param max_frames_mask_fraction: limits the size of the frame (temporal) mask to this value times the length
+            of the utterance (or supervision segment).
+            This is the parameter denoted by ``p`` in the SpecAugment paper.
+        :param p: the probability of applying this transform.
+            It is different from ``p`` in the SpecAugment paper!
+        """
+        super().__init__()
+        assert 0 <= p <= 1
+        assert num_feature_masks >= 0
+        assert num_frame_masks > 0
+        assert features_mask_size > 0
+        assert frames_mask_size > 0
+        self.time_warp_factor = time_warp_factor
+        self.num_feature_masks = num_feature_masks
+        self.features_mask_size = features_mask_size
+        self.num_frame_masks = num_frame_masks
+        self.frames_mask_size = frames_mask_size
+        self.max_frames_mask_fraction = max_frames_mask_fraction
+        self.p = p
+
+    def forward(
+        self,
+        features: torch.Tensor,
+        supervision_segments: Optional[torch.IntTensor] = None,
+        *args,
+        **kwargs,
+    ) -> Tuple[torch.Tensor, torch.Tensor]:
+        """
+        Computes SpecAugment for a batch of feature matrices.
+
+        Since the batch will usually already be padded, the user can optionally
+        provide a ``supervision_segments`` tensor that will be used to apply SpecAugment
+        only to selected areas of the input. The format of this input is described below.
+
+        :param features: a batch of feature matrices with shape ``(B, T, F)``.
+        :param supervision_segments: an int tensor of shape ``(S, 3)``. ``S`` is the number of
+            supervision segments that exist in ``features`` -- there may be either
+            less or more than the batch size.
+            The second dimension encoder three kinds of information:
+            the sequence index of the corresponding feature matrix in `features`,
+            the start frame index, and the number of frames for each segment.
+        :return: an augmented tensor of shape ``(B, T, F)``.
+        """
+        assert len(features.shape) == 3, (
+            "SpecAugment only supports batches of "
+            "single-channel feature matrices."
+        )
+        features = features.clone()
+        # 1 (True) represents masked area;
+        # 0 (False) represents original un-masked area.
+        time_masked_area = torch.zeros_like(features)
+        if supervision_segments is None:
+            # No supervisions - apply spec augment to full feature matrices.
+            for sequence_idx in range(features.size(0)):
+                (
+                    features[sequence_idx],
+                    time_masked_area[sequence_idx],
+                ) = self._forward_single(features[sequence_idx])
+
+        else:
+            # Supervisions provided - we will apply time warping only on the supervised areas.
+            for sequence_idx, start_frame, num_frames in supervision_segments:
+                end_frame = start_frame + num_frames
+                (
+                    features[sequence_idx, start_frame:end_frame],
+                    time_masked_area[sequence_idx, start_frame:end_frame],
+                ) = self._forward_single(
+                    features[sequence_idx, start_frame:end_frame],
+                    warp=True,
+                    mask=False,
+                )
+            # ... and then time-mask the full feature matrices. Note that in this mode,
+            # it might happen that masks are applied to different sequences/examples
+            # than the time warping.
+            for sequence_idx in range(features.size(0)):
+                (
+                    features[sequence_idx],
+                    time_masked_area[sequence_idx],
+                ) = self._forward_single(
+                    features[sequence_idx], warp=False, mask=True
+                )
+
+        return features, time_masked_area
+
+    def _forward_single(
+        self, features: torch.Tensor, warp: bool = True, mask: bool = True
+    ) -> Tuple[torch.Tensor, torch.Tensor]:
+        """
+        Apply SpecAugment to a single feature matrix of shape (T, F).
+        """
+        time_masked_area = torch.zeros_like(features)
+        if random.random() > self.p:
+            # Randomly choose whether this transform is applied
+            # No augmentation, no masked area.
+            return features, time_masked_area
+        if warp:
+            if self.time_warp_factor is not None and self.time_warp_factor >= 1:
+                features = time_warp(features, factor=self.time_warp_factor)
+        if mask:
+            mean = features.mean()
+            # Frequency masking
+            features, _ = mask_along_axis_optimized(
+                features,
+                mask_size=self.features_mask_size,
+                mask_times=self.num_feature_masks,
+                mask_value=mean,
+                axis=2,
+            )
+            # Time masking
+            max_tot_mask_frames = self.max_frames_mask_fraction * features.size(
+                0
+            )
+            num_frame_masks = min(
+                self.num_frame_masks,
+                math.ceil(max_tot_mask_frames / self.frames_mask_size),
+            )
+            max_mask_frames = min(
+                self.frames_mask_size, max_tot_mask_frames // num_frame_masks
+            )
+            features, time_masked_area = mask_along_axis_optimized(
+                features,
+                mask_size=max_mask_frames,
+                mask_times=num_frame_masks,
+                mask_value=mean,
+                axis=1,
+            )
+
+        return features, time_masked_area
+
+    def state_dict(self) -> Dict:
+        return dict(
+            time_warp_factor=self.time_warp_factor,
+            num_feature_masks=self.num_feature_masks,
+            features_mask_size=self.features_mask_size,
+            num_frame_masks=self.num_frame_masks,
+            frames_mask_size=self.frames_mask_size,
+            max_frames_mask_fraction=self.max_frames_mask_fraction,
+            p=self.p,
+        )
+
+    def load_state_dict(self, state_dict: Dict):
+        self.time_warp_factor = state_dict.get(
+            "time_warp_factor", self.time_warp_factor
+        )
+        self.num_feature_masks = state_dict.get(
+            "num_feature_masks", self.num_feature_masks
+        )
+        self.features_mask_size = state_dict.get(
+            "features_mask_size", self.features_mask_size
+        )
+        self.num_frame_masks = state_dict.get(
+            "num_frame_masks", self.num_frame_masks
+        )
+        self.frames_mask_size = state_dict.get(
+            "frames_mask_size", self.frames_mask_size
+        )
+        self.max_frames_mask_fraction = state_dict.get(
+            "max_frames_mask_fraction", self.max_frames_mask_fraction
+        )
+        self.p = state_dict.get("p", self.p)
+
+
+def mask_along_axis_optimized(
+    features: torch.Tensor,
+    mask_size: int,
+    mask_times: int,
+    mask_value: float,
+    axis: int,
+) -> Tuple[torch.Tensor, torch.Tensor]:
+    """
+    Apply Frequency and Time masking along axis.
+    Frequency and Time masking as described in the SpecAugment paper.
+
+    :param features: input tensor of shape ``(T, F)``
+    :mask_size: the width size for masking.
+    :mask_times: the number of masking regions.
+    :mask_value: Value to assign to the masked regions.
+    :axis: Axis to apply masking on (1 -> time, 2 -> frequency)
+    """
+    if axis not in [1, 2]:
+        raise ValueError("Only Frequency and Time masking are supported!")
+
+    # 1 (True) represents masked area;
+    # 0 (False) represents original un-masked area.
+    masked_area = torch.zeros_like(features)
+    features = features.unsqueeze(0)
+    masked_area = masked_area.unsqueeze(0)
+    features = features.reshape([-1] + list(features.size()[-2:]))
+
+    values = torch.randint(int(0), int(mask_size), (1, mask_times))
+    min_values = torch.rand(1, mask_times) * (features.size(axis) - values)
+    mask_starts = (min_values.long()).squeeze()
+    mask_ends = (min_values.long() + values.long()).squeeze()
+
+    if axis == 1:
+        if mask_times == 1:
+            features[:, mask_starts:mask_ends] = mask_value
+            return features.squeeze(0), masked_area
+        for (mask_start, mask_end) in zip(mask_starts, mask_ends):
+            features[:, mask_start:mask_end] = mask_value
+            masked_area[:, mask_start:mask_end] = 1
+    else:
+        if mask_times == 1:
+            features[:, :, mask_starts:mask_ends] = mask_value
+            masked_area[:, :, mask_starts:mask_ends] = 1
+            return features.squeeze(0), masked_area
+        for (mask_start, mask_end) in zip(mask_starts, mask_ends):
+            features[:, :, mask_start:mask_end] = mask_value
+            masked_area[:, :, mask_start:mask_end] = 1
+
+    features = features.squeeze(0)
+    masked_area = masked_area.squeeze(0)
+    return features, masked_area
+
+
+def time_warp(features: torch.Tensor, factor: int) -> torch.Tensor:
+    """
+    Time warping as described in the SpecAugment paper.
+    Implementation based on Espresso:
+    https://github.com/freewym/espresso/blob/master/espresso/tools/specaug_interpolate.py#L51
+
+    :param features: input tensor of shape ``(T, F)``
+    :param factor: time warping parameter.
+    :return: a warped tensor of shape ``(T, F)``
+    """
+    t = features.size(0)
+    if t - factor <= factor + 1:
+        return features
+    center = np.random.randint(factor + 1, t - factor)
+    warped = np.random.randint(center - factor, center + factor + 1)
+    if warped == center:
+        return features
+    features = features.unsqueeze(0).unsqueeze(0)
+    left = torch.nn.functional.interpolate(
+        features[:, :, :center, :],
+        size=(warped, features.size(3)),
+        mode="bicubic",
+        align_corners=False,
+    )
+    right = torch.nn.functional.interpolate(
+        features[:, :, center:, :],
+        size=(t - warped, features.size(3)),
+        mode="bicubic",
+        align_corners=False,
+    )
+    return torch.cat((left, right), dim=2).squeeze(0).squeeze(0)
diff --git a/egs/librispeech/ASR/pruned_transducer_stateless6/model.py b/egs/librispeech/ASR/pruned_transducer_stateless6/model.py
index 66bb33e8d0..305049d692 100644
--- a/egs/librispeech/ASR/pruned_transducer_stateless6/model.py
+++ b/egs/librispeech/ASR/pruned_transducer_stateless6/model.py
@@ -23,7 +23,7 @@
 
 from icefall.utils import add_sos
 
-from quantization.prediction import JointCodebookLoss
+from multi_quantization.prediction import JointCodebookLoss
 
 
 class Transducer(nn.Module):
@@ -41,6 +41,8 @@ def __init__(
         joiner_dim: int,
         vocab_size: int,
         num_codebooks: int = 0,
+        masked_scale: float = 1.0,
+        unmasked_scale: float = 1.0,
     ):
         """
         Args:
@@ -60,6 +62,10 @@ def __init__(
             contains unnormalized probs, i.e., not processed by log-softmax.
           num_codebooks:
             Used by distillation loss.
+          masked_scale:
+            scale of codebook loss of masked area.
+          unmasked_scale:
+            scale of codebook loss of unmasked area.
         """
         super().__init__()
         assert isinstance(encoder, EncoderInterface), type(encoder)
@@ -75,8 +81,12 @@ def __init__(
         self.simple_lm_proj = ScaledLinear(decoder_dim, vocab_size)
         if num_codebooks > 0:
             self.codebook_loss_net = JointCodebookLoss(
-                predictor_channels=encoder_dim, num_codebooks=num_codebooks
+                predictor_channels=encoder_dim,
+                num_codebooks=num_codebooks,
+                reduction="none",
             )
+        self.masked_scale = masked_scale
+        self.unmasked_scale = unmasked_scale
 
     def forward(
         self,
@@ -88,6 +98,7 @@ def forward(
         lm_scale: float = 0.0,
         warmup: float = 1.0,
         codebook_indexes: torch.Tensor = None,
+        time_masked_area: torch.Tensor = None,
     ) -> torch.Tensor:
         """
         Args:
@@ -113,6 +124,8 @@ def forward(
             warmup > 1 "are fully warmed up" and all modules will be active.
           codebook_indexes:
             codebook_indexes extracted from a teacher model.
+          time_masked_area:
+            masked area by SpecAugment, 1 represents masked.
         Returns:
           Return the transducer loss.
 
@@ -140,6 +153,22 @@ def forward(
             codebook_loss = self.codebook_loss_net(
                 middle_layer_output, codebook_indexes
             )
+            codebook_loss = codebook_loss.reshape(codebook_indexes.shape)
+            target_t = codebook_loss.shape[1]
+            time_masked_area = time_masked_area.bool()
+            time_masked_area = time_masked_area[
+                :, : target_t * 4 : 4, 0  # noqa E203
+            ]
+            assert time_masked_area.shape == codebook_loss.shape[:-1]
+            time_masked_area = time_masked_area.unsqueeze(2).to(
+                codebook_loss.device
+            )
+            masked_loss = (time_masked_area * codebook_loss).sum()
+            unmasked_loss = (~time_masked_area * codebook_loss).sum()
+            codebook_loss = (
+                self.masked_scale * masked_loss
+                + self.unmasked_scale * unmasked_loss
+            )
         else:
             # when codebook index is not available.
             codebook_loss = None
diff --git a/egs/librispeech/ASR/pruned_transducer_stateless6/train.py b/egs/librispeech/ASR/pruned_transducer_stateless6/train.py
index feb58f457b..3cec4326e9 100755
--- a/egs/librispeech/ASR/pruned_transducer_stateless6/train.py
+++ b/egs/librispeech/ASR/pruned_transducer_stateless6/train.py
@@ -177,6 +177,18 @@ def get_parser():
         changed.""",
     )
 
+    parser.add_argument(
+        "--masked-scale",
+        type=float,
+        default=1.0,
+    )
+
+    parser.add_argument(
+        "--unmasked-scale",
+        type=float,
+        default=1.0,
+    )
+
     parser.add_argument(
         "--lr-batches",
         type=float,
@@ -378,6 +390,8 @@ def get_params() -> AttributeDict:
             # two successive codebook_index are concatenated together.
             # Detailed in function Transducer::concat_sucessive_codebook_indexes.
             "num_codebooks": 16,  # used to construct distillation loss
+            "masked_scale": 1.0,
+            "unmasked_scale": 1.0,
         }
     )
 
@@ -436,6 +450,8 @@ def get_transducer_model(params: AttributeDict) -> nn.Module:
         num_codebooks=params.num_codebooks
         if params.enable_distiallation
         else 0,
+        masked_scale=params.masked_scale,
+        unmasked_scale=params.unmasked_scale,
     )
     return model
 
@@ -602,7 +618,7 @@ def compute_loss(
         if isinstance(model, DDP)
         else next(model.parameters()).device
     )
-    feature = batch["inputs"]
+    feature, time_masked_area = batch["inputs"]
     # at entry, feature is (N, T, C)
     assert feature.ndim == 3
     feature = feature.to(device)
@@ -631,6 +647,7 @@ def compute_loss(
             lm_scale=params.lm_scale,
             warmup=warmup,
             codebook_indexes=codebook_indexes,
+            time_masked_area=time_masked_area,
         )
         # after the main warmup step, we keep pruned_loss_scale small
         # for the same amount of time (model_warm_step), to avoid
@@ -1089,7 +1106,9 @@ def main():
     parser = get_parser()
     LibriSpeechAsrDataModule.add_arguments(parser)
     args = parser.parse_args()
-    args.exp_dir = Path(args.exp_dir)
+    args.exp_dir = Path(
+        f"{args.exp_dir}-masked_scale-{args.masked_scale}-un-{args.unmasked_scale}-{args.spec_aug_max_frames_mask_fraction}"
+    )
 
     world_size = args.world_size
     assert world_size >= 1
diff --git a/egs/librispeech/ASR/tdnn_lstm_ctc/asr_datamodule.py b/egs/librispeech/ASR/tdnn_lstm_ctc/asr_datamodule.py
index e83009d4a0..b391b28150 100644
--- a/egs/librispeech/ASR/tdnn_lstm_ctc/asr_datamodule.py
+++ b/egs/librispeech/ASR/tdnn_lstm_ctc/asr_datamodule.py
@@ -32,7 +32,6 @@
     K2SpeechRecognitionDataset,
     PrecomputedFeatures,
     SingleCutSampler,
-    SpecAugment,
 )
 from lhotse.dataset.input_strategies import (  # noqa F401 For AudioSamples
     AudioSamples,
@@ -41,6 +40,7 @@
 from lhotse.utils import fix_random_seed
 from torch.utils.data import DataLoader
 
+from aug import SpecAugment
 from icefall.utils import str2bool
 
 
@@ -183,6 +183,12 @@ def add_arguments(cls, parser: argparse.ArgumentParser):
             help="When enabled, use SpecAugment for training dataset.",
         )
 
+        group.add_argument(
+            "--spec-aug-max-frames-mask-fraction",
+            type=float,
+            default=0.15,
+        )
+
         group.add_argument(
             "--spec-aug-time-warp-factor",
             type=int,
@@ -272,6 +278,7 @@ def train_dataloaders(
                     features_mask_size=27,
                     num_feature_masks=2,
                     frames_mask_size=100,
+                    max_frames_mask_fraction=self.args.spec_aug_max_frames_mask_fraction,
                 )
             )
         else: