diff --git a/egs/libriheavy/TTS/local/prepare_manifest.py b/egs/libriheavy/TTS/local/prepare_manifest.py
index 0c01ded2d..3225899bd 100755
--- a/egs/libriheavy/TTS/local/prepare_manifest.py
+++ b/egs/libriheavy/TTS/local/prepare_manifest.py
@@ -1,5 +1,5 @@
 #!/usr/bin/env python3
-# Copyright    2023  Xiaomi Corp.        (authors: Wei Kang)
+# Copyright    2024  Xiaomi Corp.        (authors: Yifan Yang)
 #
 # See ../../../../LICENSE for clarification regarding multiple authors
 #
@@ -28,9 +28,10 @@ from tqdm import tqdm
 from icefall.utils import str2bool
 
 
-class TextNormlizer:
+class TextNormalizer:
     def __init__(self):
         self.en_tn_model = EnNormalizer(cache_dir="/tmp/tn", overwrite_cache=False)
+        self.table = str.maketrans("’‘，。；？！（）：-《》、“”【】", "'',.;?!(): <>/\"\"[]")
 
     def __call__(self, cut):
         text = cut["supervisions"][0]["custom"]["texts"][0]
@@ -40,8 +41,7 @@ class TextNormlizer:
         text = re.sub(r"\([^\)]*\)", " ", text)
 
         # Apply mappings
-        table = str.maketrans("’‘，。；？！（）：-《》、“”【】", "'',.;?!(): <>/\"\"[]")
-        text = text.translate(table)
+        text = text.translate(self.table)
 
         # Remove extra spaces
         text = re.sub(r"\s+", " ", text).strip()
@@ -61,18 +61,15 @@ def main():
     fname = Path(sys.argv[1]).name
     oname = Path(sys.argv[2]) / fname
 
-    tn = TextNormlizer()
-    with gzip.open(sys.argv[1], "r") as fin, ProcessPoolExecutor() as ex:
-        futures = []
-        cuts = []
-        for line in tqdm(fin, desc="Distributing tasks"):
-            cut = json.loads(line)
-            futures.append(ex.submit(tn, cut))
+    tn = TextNormalizer()
+    with ProcessPoolExecutor() as ex:
+        with gzip.open(sys.argv[1], "r") as fin:
+            cuts = (json.loads(line) for line in fin)
+            results = ex.map(tn, cuts)
 
-    with gzip.open(oname, "w") as fout:
-        for future in tqdm(futures, desc="Processing"):
-            cut = future.result()
-            fout.write((json.dumps(cut) + "\n").encode())
+        with gzip.open(oname, "w") as fout:
+            for cut in tqdm(results, desc="Processing"):
+                fout.write((json.dumps(cut) + "\n").encode())
 
 
 if __name__ == "__main__":