diff --git a/future.html b/future.html
index dd04848..04b37ad 100644
--- a/future.html
+++ b/future.html
@@ -31,7 +31,6 @@ <h1>Future Additions</h1>
 			<li>Immorpher - Add a guide on making custom palettes</li>
 			<li>Immorpher - Door and key guide</li>
 			<li>Immorpher - Bridge guide</li>
-			<li>agony ZENITH - Add a note on two line defs needed for sound blocking</li>
 		</ul>
 	</div>
 
diff --git a/maps/lineflags.html b/maps/lineflags.html
index 515884b..394bba2 100644
--- a/maps/lineflags.html
+++ b/maps/lineflags.html
@@ -38,7 +38,7 @@ <h1>Line Flags</h1>
 			<tr><td>0x8</td><td>Upper Unpegged</td><td>Align upper texture from ceiling origin</td></tr>
 			<tr><td>0x10</td><td>Lower Unpegged</td><td>Align lower texture from ceiling origin</td></tr>
 			<tr><td>0x20</td><td>Show 1-sided on Automap</td><td>Show line as one-sided with automap (good for secrets)</td></tr>
-			<tr><td>0x40</td><td>Block Sound</td><td>Prevent sound from alerting monsters across this linedef (sound can still be heard)</td></tr>
+			<tr><td>0x40</td><td>Block Sound</td><td>Prevent sound from alerting monsters across this linedef (sound can still be heard). In practice two linedefs with this flag are required to successfully prevent an alerting sound from traveling.</td></tr>
 			<tr><td>0x80</td><td>Never Show on Automap</td><td>Never show the linedef on automap</td></tr>
 			<tr><td>0x100</td><td>Always Show on Automap</td><td>Always show the linedef on automap</td></tr>
 			<tr><td>0x200</td><td>Render Middle Texture</td><td>Show middle texture (good for windows and cages)</td></tr>