Similar to the human senses of smell, touch, sight, and hearing, a healthy indoor environment reflects at least four senses: indoor air quality, thermal comfort, illumination, and acoustic comfort. This article discusses the fourth sense: acoustic comfort.

Acoustical comfort is a perception and relates to the level (intensity) and character (frequency) of sound. Acoustic discomfort might be caused by sounds that prevent normal conversation and peaceful rest, or are simply distractive … these are noises. For the purposes of this discussion, noise describes sound that is undesirable.

Indoor environments include distinctly different spaces with respect to sound. Media centers and music rooms need to contain sound without creating distortion. Living and family rooms and libraries need to allow normal conversation and contemplation. Sleeping areas need to allow peaceful rest. Acoustic comfort must accommodate all of these needs. Let’s discuss how this is approached.

First, let’s recognize: Sounds for some = noises for others …

Sound can be distractive (noise) even when the level (intensity) is not great. Examples include the rumble of a passing train (low frequency) or the punctuating sound of referee’s whistle (narrow frequency) over a roaring crowd (broad frequency; white noise).

Sometimes certain sounds can be distractive (noise) even when it’s quiet and regardless of frequency. For example, a barking dog bothers my wife and I hardly notice. A baby’s distant whimper alarms a mother; whereas the father’s TV concentration is unbroken.

Ensuring acoustic comfort requires considering all forms of sound. In order to attenuate (reduce) undesired sound (noise), the sound must first be measured. Sound level and frequency are measured with a meter such as illustrated in the adjacent photograph.

The illustrated meter is on my office desk with background Christmas music. Note the bar indicators on the screen. The center bars indicate sound levels at specific frequencies and the two far-right bars along with the value in the right corner represent overall sound level (59.4 decibels). The sound frequencies represent the range of normal human speech (singing). The overall sound level and frequencies are not distractive to me … hey, it’s Christmas music!

Having measured sound levels and frequencies, how do we specify noise abatement? We first need to understand noise measurements and how they relate to our hearing.

Decibel (dB). The decibel is the most commonly used measurement for sound level (intensity). Human perception of loudness varies based upon frequency. We cannot hear sounds with frequencies below about 20 Hertz) or above about 20,000 Hertz. We hear well within the frequency range of normal human speech, but our hearing diminishes below 1,000 Hertz and above 6,000 Hertz. Normal human conversation is between 500 Hertz and 6,000 Hertz (frequency) and at 60 decibels (intensity).

Perspective for sound levels in different setting is provided in the following table (http://www.engineeringtoolbox.com/sound-level-d_719.html):


Sone. Sone is a common specification for sound produced by fans, such as bathroom exhaust fans. Doubling the sones is equivalent to doubling the perceived sound level. [Adding six decibels is approximately equivalent to doubling the perceived sound level measured in decibels.]

Perspective for sound levels in different settings is provided in the adjacent table (http://www.designerhardware.com/files/HelpWin/Sone.html):

Once we know sound level and frequency, we can specify appropriate measures to attenuate (reduce) undesired sound (noise).

Sound Transmission Class (STC). This is a comparative measure of how well different materials attenuate sound. STC is used to specify materials or construction configurations that attenuate noise.

The following table offers perspective related to STC and sound attenuation (http://en.wikipedia.org/wiki/Sound_transmission_class):

I hope that you have caught that noise is not as simple as hearing; and, shutting out noise is not as simple as covering our ears. This article provides a simple overview of providing acoustical comfort for your indoor environment:

- Identify noise sources
- Measure sound level and frequency
- Determine acceptable sound levels
- Specify appropriate attenuation measures

Acoustic comfort is as critical to our indoor environment as hearing is to our human condition. Acoustic Comfort is peace and quiet … and affects your family’s enjoyment and wellbeing!

Filed under: Building Diagnostics, Green Homes, Indoor Environment Quality