Reverberation Time Testing

From ensuring clear speech, to providing fullness in music. 

Rooms for Speech

Clear speech is essential in many environments. Ensure your speech will be clearly understood.

Concert Auditoria

Deliver well rounded and warm musical tones.

Multi Purpose Spaces

Or find the balance between warm full music, and clear ineligible speech.

Depending on the intended use, the optimal reverberation time for a given space can vary by several seconds!

Reverberation time, often called an RT60 is the time that takes a sound level to decay by 60 dB once the source has ceased. A sound test that measures time taken for a noise to decay by 60 dB, may seem arbitrary. However, in the assessment of performance spaces, this 60 dB drop represents the approximate dynamic range of a live orchestra. Having a standardised level of decay allows us to formalise the assessment procedure, which means we can reliably compare different spaces.

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T: 0845 508 0890

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Decay of Sound

Sound transmission occurs as a result of a series of vibrations within a given medium. When discussing airborne sound, one of the primary reasons for the speed of sound decay is contact with surfaces within a room. As particles in the air move back and forth, friction caused by contact with these elements will cause this kinetic energy to be converted into heat. As acoustic energy is removed from the system, the sound becomes softer. Different types of material will have different effects on a given sound, and will affect different parts of the frequency range. By understanding these differences, we can control the degree to which sound will decay within a given space.

The Best Reverberation Time?

Depending on the intended use, the optimal reverberation time for a given space will vary by several seconds. If the main concern is communication, and therefore speech intelligibility, a much shorter reverberation time will be desirable. On the other hand, the blend of notes in classical music that results from longer reverberation times often improves how pleasing the music sounds.

Below is a brief list of example spaces, along with their reverberation times.

Anechoic chamber – designed to simulate a free field – 0s

Typical bedroom – sleeping, daytime resting – 0.5s

Typical lecture hall – speech and communication – 1s

Boston Symphony Hall – Classical music performance – 1.8s.

Inchindown oil tank  – 5.6 million gallon storage tank in Scotland – 75s

How is it Controlled

Generally speaking, reverberation time is proportional to the volume of the space, and inversely proportional to the amount of absorption. So smaller spaces containing soft furnishings will be ideal for speech intelligibility. Whereas larger spaces with less absorption will provide more fullness and intimacy in music performance.

Use in Sound Insulation Testing

A longer reverberation time within a space will allow noise to build up to a higher level. Conversely, a room containing a large amount of absorption will cause sound to decay at a much higher rate. When undertaking a sound insulation test, this fact could provide misleading results. A “highly reflective” receiver room will retain more noise, as a result higher noise levels will be measured. This will be true irrespective of the actual performance of the partition. Because of this, we must apply a correction to account for reverberation time, and normalise the measured sound level difference. This allows us to directly compare different partitions, without having to worry about the level of reverberation in the respective spaces.

T: 0845 508 0890
M: 0787 245 0205

E: bgroves@completelysound.co.uk

A: The Glider Business Centre,
65 Lowther Road,
Dunstable, LU6 3NL

T: 0845 508 0890
M: 0787 247 0205

E: bgroves@completelysound.co.uk