When trying to quantify acoustics, most of us tend to focus solely on volume. That is, we’re only concerned with how loud an environment is. This focus often leads to an overemphasis on reducing noise through blocking and absorption (a fixation I’ve called the ‘Quest for Silence’ in previous posts).
However, there are many more measurable aspects of acoustical performance and I’d like to talk about one of them today: dynamic range.
This term is defined as the change in volume over time – from the peaks down to the background level. While there’s no independent technical definition, let’s consider a standardized range to be between the top 5% and bottom 5% of volumes, which captures the variation that occurs 90% of the time while avoiding extremes in either direction.
How comfortable you feel in a space has a lot to do with its dynamic range. Generally, the higher the range, the less comfortable you’ll be. That’s because it’s very difficult for us to ignore intermittent noises or volume changes that are dramatically higher than the background sound level in a space. Our senses are attuned to such changes in our environment and they can even trigger our stress – or ‘fight or flight’ – response.
Comparing these changes in sound to changes in lighting might be helpful. Imagine you’re sitting in a room and someone starts using a dimmer switch to intermittently cause large swings in the lighting levels. Feeling irritated?
If you’re a boater, you probably feel the same way about waves. The smaller they are, the more comfortable your time on the water. The larger they are, the more difficult to ignore (particularly if you suffer from motion sickness).
The same is true for acoustics – the lower the variation in volume levels in the space, the less disruption you’ll experience to your concentration and overall comfort.
The interesting part about this way of assessing acoustics is that high dynamic range doesn't only occur in spaces that we consider ‘loud,’ but also in those that otherwise measure low in terms of volume. A space that typically has low levels of background sound punctuated by intermittent noises is likely to exhibit high dynamic range, even if the volume of those noises isn’t that high. That’s because it’s the magnitude of the difference between the base level and peak volumes that affects us.
A high dynamic range may indicate that insufficient efforts have been taken to control the peaks and background level in a space. In order to reduce the peaks, you should try to eliminate, contain and absorb as much noise as possible. However, note that these strategies alone likely won’t be enough to reduce dynamic range and, in some cases, they can even increase it because they also reduce the level of background sound in the space.
In order to successfully minimize volume variation over time, you need to use a sound masking system. This technology will provide a consistent background (or ambient) sound level, making any intermittent noises less noticeable and disruptive. Plus any noises below the level of the masking sound will be covered up and/or far less noticeable.