diff --git a/src/ISM.jl b/src/ISM.jl
index f27eac8..d8601eb 100644
--- a/src/ISM.jl
+++ b/src/ISM.jl
@@ -36,7 +36,8 @@ function ISM(
     room::RectangularRoom,
     config::ISMConfig;
 )
-    h = config.N
+    h = zeros(config.N)
+    # TODO: h = zeros(T, config.N)
     ISM!(h, tx, rx, room, config)
 
     if config.hp