An interesting development has occurred in recent times: folks have become much more aware that the acoustic space plays a critical role with respect to the final sound of the room.

In other words, unless you “fix the room,” changing the sound system may in fact not solve the problem at all.

And truth be known, bringing the room acoustics up to an “acceptable level” is often actually easier than setting up a PA system! 

Testing One, Two, Clap
Go into the room, clap your hands. If the trailing echo and reverb is longer than 1 second, it will affect the intelligibility of the system.

Intelligibility is a term that describes our ability to understand what is being said. Back in the dark ages, Gregorian chant was perfectly suited for the long trailing reverb that was common in houses of worship.

And the spoken word? Only the elite could speak and understand Latin, so for the average person, following the sermon had very little to do with understanding the message.

Today this has changed. Music has become rhythmic; the language in the church, nightclub or conference center is the language of the people. It is all about communicating a message.

And for this to be effective, the message must be clear.

Solving The Problem
This article is not about creating a performing arts center out of a gymnasium. It’s about reducing the reverberant field so that the sound system can actually do its job.

Equal-loudness contours shown in red (from ISO 226:2003 revision) and Fletcher-Munson curves shown in blue for comparison.(click to enlarge)

Acousticians are specialists that have the expertise to deliver optimized high-end rooms. Here, we’re only going to tackle the basics so that you can turn a problem space into an acceptable one.

The human voice ranges from 200 Hz to about 4 kHz, with a peak in around 500 Hz. The louder we speak, the more accentuated our voice will be in the mid range.

Fletcher-Munson curves show us that human hearing is also most sensitive to the mid range. This provides us with the first key ingredient to improving intelligibility: we need to focus our attention on the mid range. 

The next bit that we need to consider is that low frequencies have much more energy than high frequencies. And further, that bass frequencies below 300 Hz are deemed to be omnidirectional and high frequencies tend to beam like a flashlight.

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