Reverberation

Definition

Per Wikipedia: Reverberation:

Reverberation (also known as reverb), in acoustics, is a persistence of sound, after a sound is produced.

[...]

reverberation is the occurrence of reflections that arrive in a sequence of less than approximately 50 ms.

If the reflections arrive after 50-100ms, it is considered "echo".

Measurement

The reverberation is quantified by the time it takes for the original sound to decay by 60dB, denoted as \(T_{60}\) or \(RT_{60}\).

Per RECOMMENDED REVERBERATION TIMES FOR 7 KEY SPACES, the recommended \(RT_{60}\) for the following spaces are:

• Kindergarten: 0.4s
• Offices: 0.4-0.7s
• Classrooms: 0.4-0.6s
• Music rehearsal rooms: 0.9-1.2s
• Homes: 0.9s
• Bedrooms: 0.5s
• Restaurants: 0.7-0.8s

Minimum Reverberation Time Human Can Perceive

There seems no immediate answer on the Internet to the question about the minimum \(RT_{60}\) that a typical human will describe a sound as "reverberant." But according to Aalto University: The human ear detects half a millisecond delay in sound, human can perceive "a half of a millisecond delay" in certain frequencies.

The study shows that people can hear differences when audio starts at certain frequencies ahead of time. A half of a millisecond delay in certain frequencies relative to others was also audible. The amount of delay needed to exceed the detection threshold varies considerably at different frequencies, but delays were especially heard when sounds started or stopped