Level
Cantrip
Casting Time
1 Action
Range/Area
5 ft.
Components
S
Duration
Instantaneous
School
Evocation
Attack/Save
CON Save
Damage/Effect
Thunder
You create a burst of thunderous sound that can be heard up to 100 feet away. Each creature within range, other than you, must succeed on a Constitution saving throw or take 1d6 thunder damage.
The spell’s damage increases by 1d6 when you reach 5th level (2d6), 11th level (3d6), and 17th level (4d6).
I read this to basically mean range is adjacent to caster
that's only how far it can be heard, so it's not subtle. Range it 5ft
the noise can be heard 100' away. The spell effects only 5' away from caster.
Hi
Take for example Fireball, it says similar, Range 150, you can select any point from you and the top range distance (150ft), in this case the range is just 5 ft, any square from you at 5ft is an option, then any creature within the range receive the damage, but the difference is that fireball specify the area in radius ft.
found this in Xanathars book
Areas of Effect on a Grid
The Dungeon Master’s Guide includes the following short rule for using areas of effect on a grid.
Choose an intersection of squares as the point of origin of an area of effect, then follow the rules for that kind of area as normal (see the “Areas of Effect” section in chapter 10 of the Player’s Handbook). If an area of effect is circular and covers at least half a square, it affects that square.