The perfect room has a depth that is three times the rooms width, lower ceilings or reflective clouds, stadium seating, thick outer walls, and diffusion on the walls along with absorption. There are always exceptions, but as a guideline these elements work quite well in unison, and many premier concert halls and performance venues have been built with these concepts in mind.
Below is a more detailed look at what all those phrases actually mean, and why they matter!
Take the 3:1 rule for example – which states that rooms should be three times deeper than they are wide. The concept behind this rule is that the long side walls are closer to the majority of the audience and provide early lateral reflections.
Envelopment describes the listener’s sense of being surrounded by the music as well as the presence of the sound, and is typified by your sense that the music is being created right in front of you rather than on a stage a hundred feet away.
In performance spaces, envelopment is the attribute that supports participation from the audience and congregational singing. One of the common mistakes in acoustics is to only use absorption on the side walls of an auditorium which deadens all lateral reflections and leads to less participation.
In other words, if you want people to sing and respond to the action on stage then envelopment should be considered when designing or changing a space.
Using Reflections Correctly
Early reflections have a large impact on the subjective pleasing nature of the sound. Lower ceilings and reflective clouds have similar effects to the longer side walls – they allow for faster reflections to the listener. Generally, we perceive any sounds arriving between 35 milliseconds of each other to be the same sound. Reflections arriving less than 20 milliseconds from each other add to the pleasing or intimate nature of a sound while any reflections arriving after 50 milliseconds or greater are destructive to the original sound.
Simply put, large spaces have a more difficult time managing early and late reflections because of the greater distance between the walls or ceiling and the audience. As acoustics designers, we use ceiling clouds and reflective panels to artificially create the sonic signature of the room.
Stadium seating allows for greater clarity to each listener as they have an un-obstructed listening path to the initial sound. That’s right – it’s about more than just a better view!