User manual

Reverberation Time RT60

The XL2 measures the energy decay from 63 Hz to

8 kHz using the Schroeder method in 1/1 octave resolution. The

optional Extended Acoustic Pack enables 1/3 octave band reso-

lution from 50 Hz to 10 kHz. Use either an impulse source (e.g.,

a starter pistol) or an interrupted pink noise as the test signal.

What is Reverberation Time RT60?

Reverberation time RT60 is the time required for the sound

pressure level to decrease by 60 dB after the sound stimulus

signal is stopped. For simple practical measurements the ap-

plicable standard ISO 3382 and ASTM E2235 speciﬁes the fol-

lowing two measurement methods:

T20•

The measurement requires just a small dynamic measure-

ment range of ~35 dB above the ambient noise level for

each frequency band.

RT60 (T20) = 3 x decay time of 20 dB

T30•

The measurement requires a dynamic measurement

range of ~45 dB above the ambient noise level for each

frequency band.

RT60 (T30) = 2 x decay time of 30 dB

In detail, the RT60 is based on a linear least-squares regres-

sion of the measured decay curve. If the overall RT60 is short

(e.g. < 0.3 seconds) the room acoustic is referred to as be-

ing “dead”; for example, a heavily furnished room with thick

carpets, curtains and upholstered furniture may have such an

acoustic character. If the overall RT60 is long (say more than

2 seconds) the room acoustic is referred to as being “live” and

echoic; for example, a large empty room with painted plaster

walls and a tiled ﬂoor may have such an acoustic character.

Level [dB]

0 dB

-5 dB

-25 dB

-35 dB

Time

distance to

noise ﬂoor

20 dB level range to

obtain the reverbera-

tion time

RT60 Measurement with T20 method