What is RT60?

In the simplest of terms, the “RT60” is the amount of time for a specific frequency to drop by 60db. For example, if a pianist plays a note, say Middle C (261.625 Hz), played at 90db then the RT60 is the amount of time it takes for that tone to drop in volume from 90db to 30db.  The overall or nominal RT60 would be the average time for a drop of 60db over a wide range of the audible frequency band.  (Usually considered to be 20Hz to 20KHz)

Typically, in a contemporary church building which balances spoken word and live music, we’re shooting for an RT60 average of around 1.25 seconds. In a classroom or office space we will often look to achieve under 1.00 seconds.  School gymnasiums can be quite high depending on the construction and size of the room but it's not uncommon to find an untreated gym or multipurpose space with an RT60 of between 3.5-5.  Although traditional cathedrals can sound amazing for choirs, organ or string instruments with a nominal RT60 as high as 7-11 seconds, that sort of reverberation time results in poor intelligibility making spoken word difficult to hear and understand.

It's important to note that a room can be too "dead" with a reverberation time that's too aggressively treated.  This can make a room feel uncomfortable and isolating.  This is not ideal for singing in a group or live music. (Like in a church or music classroom.)

Understanding that it takes a lot of work to get the RT60 of a room to be completely even, across the board at all frequencies, we typically work to try to find a balance that meets the needs of our client and their venue.