the "weight" attribute does not accept decimal values. Using 0.5 as a weight resulted in this nice little subtle error: https://minecraft.gamepedia.com/Talk:Sounds.json

gistfile1.txt

[18:40:27] [Client thread/WARN]: Invalid sounds.json
java.lang.IllegalArgumentException: Invalid weight
	at org.apache.commons.lang3.Validate.isTrue(Validate.java:155) ~[commons-lang3-3.3.2.jar:3.3.2]
	at bzf.b(SourceFile:60) ~[1.10.2.jar:?]
	at bzf.a(SourceFile:40) ~[1.10.2.jar:?]
	at bzf.a(SourceFile:23) ~[1.10.2.jar:?]
	at bzf.deserialize(SourceFile:16) ~[1.10.2.jar:?]
	at com.google.gson.TreeTypeAdapter.read(TreeTypeAdapter.java:58) ~[gson-2.2.4.jar:?]
	at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.read(TypeAdapterRuntimeTypeWrapper.java:40) ~[gson-2.2.4.jar:?]
	at com.google.gson.internal.bind.MapTypeAdapterFactory$Adapter.read(MapTypeAdapterFactory.java:187) ~[gson-2.2.4.jar:?]
	at com.google.gson.internal.bind.MapTypeAdapterFactory$Adapter.read(MapTypeAdapterFactory.java:145) ~[gson-2.2.4.jar:?]
	at com.google.gson.Gson.fromJson(Gson.java:803) ~[gson-2.2.4.jar:?]
	at com.google.gson.Gson.fromJson(Gson.java:768) ~[gson-2.2.4.jar:?]
	at bzw.a(SourceFile:119) ~[1.10.2.jar:?]
	at bzw.a(SourceFile:81) [1.10.2.jar:?]
	at bxi.a(SourceFile:100) [1.10.2.jar:?]
	at bcx.an(SourceFile:462) [1.10.2.jar:?]
	at bcx.a(SourceFile:381) [1.10.2.jar:?]
	at net.minecraft.client.main.Main.main(SourceFile:124) [1.10.2.jar:?]