diff --git a/Lib/sndhdr.py b/Lib/sndhdr.py
index a8e0a05..9f5dcc9 100644
--- a/Lib/sndhdr.py
+++ b/Lib/sndhdr.py
@@ -57,12 +57,12 @@
 
 def test_aifc(h, f):
     import aifc
-    if h.startswith(b'FORM'):
+    if not h.startswith(b'FORM'):
         return None
     if h[8:12] == b'AIFC':
         fmt = 'aifc'
     elif h[8:12] == b'AIFF':
-        fmt = b'aiff'
+        fmt = 'aiff'
     else:
         return None
     f.seek(0)
@@ -123,7 +123,7 @@
 
 
 def test_voc(h, f):
-    if h.startswith(b'Creative Voice File\032'):
+    if not h.startswith(b'Creative Voice File\032'):
         return None
     sbseek = get_short_le(h[20:22])
     rate = 0
@@ -150,7 +150,7 @@
 
 
 def test_8svx(h, f):
-    if h.startswith(b'FORM') or h[8:12] != b'8SVX':
+    if not h.startswith(b'FORM') or h[8:12] != b'8SVX':
         return None
     # Should decode it to get #channels -- assume always 1
     return '8svx', 0, 1, 0, 8
diff --git a/Lib/test/sndhdrdata/README b/Lib/test/sndhdrdata/README
new file mode 100644
index 0000000..8a17c00
--- /dev/null
+++ b/Lib/test/sndhdrdata/README
@@ -0,0 +1,12 @@
+Sound file samples used by Lib/test/test_sndhdr.py and generated using the
+following commands:
+
+   dd if=/dev/zero of=sndhdr.raw bs=20 count=1
+   sox -s -2 -c 2 -r 44100 sndhdr.raw sndhdr.<format>
+
+Sound file samples used by Lib/test/test_sndhdr.py and generated using the
+following commands:
+
+   dd if=/dev/zero of=sndhdr.raw bs=20 count=1
+   sox -s -2 -c 2 -r 44100 sndhdr.raw sndhdr.<format>
+
diff --git a/Lib/test/sndhdrdata/sndhdr.8svx b/Lib/test/sndhdrdata/sndhdr.8svx
new file mode 100644
index 0000000..8cd6cde
--- /dev/null
+++ b/Lib/test/sndhdrdata/sndhdr.8svx
Binary files differ
diff --git a/Lib/test/sndhdrdata/sndhdr.aifc b/Lib/test/sndhdrdata/sndhdr.aifc
new file mode 100644
index 0000000..8aae4e7
--- /dev/null
+++ b/Lib/test/sndhdrdata/sndhdr.aifc
Binary files differ
diff --git a/Lib/test/sndhdrdata/sndhdr.aiff b/Lib/test/sndhdrdata/sndhdr.aiff
new file mode 100644
index 0000000..8c279a7
--- /dev/null
+++ b/Lib/test/sndhdrdata/sndhdr.aiff
Binary files differ
diff --git a/Lib/test/sndhdrdata/sndhdr.au b/Lib/test/sndhdrdata/sndhdr.au
new file mode 100644
index 0000000..67c9e8f
--- /dev/null
+++ b/Lib/test/sndhdrdata/sndhdr.au
Binary files differ
diff --git a/Lib/test/sndhdrdata/sndhdr.hcom b/Lib/test/sndhdrdata/sndhdr.hcom
new file mode 100644
index 0000000..debb02d
--- /dev/null
+++ b/Lib/test/sndhdrdata/sndhdr.hcom
Binary files differ
diff --git a/Lib/test/sndhdrdata/sndhdr.sndt b/Lib/test/sndhdrdata/sndhdr.sndt
new file mode 100644
index 0000000..e1ca9cb
--- /dev/null
+++ b/Lib/test/sndhdrdata/sndhdr.sndt
Binary files differ
diff --git a/Lib/test/sndhdrdata/sndhdr.voc b/Lib/test/sndhdrdata/sndhdr.voc
new file mode 100644
index 0000000..53a91fd
--- /dev/null
+++ b/Lib/test/sndhdrdata/sndhdr.voc
Binary files differ
diff --git a/Lib/test/sndhdrdata/sndhdr.wav b/Lib/test/sndhdrdata/sndhdr.wav
new file mode 100644
index 0000000..0dca367
--- /dev/null
+++ b/Lib/test/sndhdrdata/sndhdr.wav
Binary files differ
diff --git a/Misc/ACKS b/Misc/ACKS
index 02f571a..93af016 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -433,6 +433,7 @@
 Simon Law
 Chris Lawrence
 Brian Leair
+James Lee
 John J. Lee
 Inyeol Lee
 Thomas Lee
diff --git a/Misc/NEWS b/Misc/NEWS
index 7c26473..3717942 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -78,6 +78,8 @@
 Library
 -------
 
+- Issue #9243: Fix sndhdr module and add unit tests, contributed by James Lee.
+
 - ``ast.literal_eval()`` now allows byte literals.
 
 - Issue #9137: Fix issue in MutableMapping.update, which incorrectly