Sound in rooms

Early reflections and the tail

Early reflections place the walls; the tail sizes the room.

Early reflections, then the tail

One clap as energy over time. Treat the room and compare.

Try it

  • Clap in the bare room
  • Treat the room and clap again
More on this

The first reflections tell the ear where the walls are. The tail tells it how big and how hard the room is.

This is one clap in the room, drawn as energy over time. The spikes are early reflections; the slope is the tail. Treat the room and watch both drop.

Sabine's formula estimates the reverb time from the room's volume and how much its surfaces absorb: RT60 = 0.161 × volume ÷ total absorption. A bigger room rings longer; softer surfaces shorten it.

Early reflections, roughly the first 50 ms, are not heard as echoes. They change the tone (comb filtering) and the sense of distance and room size.