Page 158 - The Master Handbook Of Acoustics

133
REVERBERATION

R 1
S R 3
Direct
A R 4

H
R 2

D R R R R 4
3
2
1
Sound pressure D D R 1
D R R R
1
B D R R 2 1 2 3

0
Time
D
R 1
R 2
Sound pressure
C R 3 R 4

0
Time
FIGURE 7-2
The buildup and decay of sound in a room. (A) The direct sound arrives first at time = 0,
reflected components arriving later. (B) The sound pressure at H builds up stepwise.
(C) The sound decays exponentially after the source ceases.

speed of sound, is about the muzzle velocity of a .22 caliber rifle,
reflected components are delayed an amount proportional to the dif-
ference in distance between the reflected path and the direct path.
The buildup of sound in a room is thus relatively slow due to finite
transit time.
The ultimate level of sound in the room is determined by the energy
going into the source S. The energy it radiates (less than the input by