This week, I made a sound art installation piece which becomes explanatory as you experience it. It is quite literally meant to be listened to from a variety of distances. Below is a transcript of the piece:
"This is a piece about the relationship between distance and the perception of sound. Specifically, it is a sonification of the Inverse Square Law. Before we begin, make sure that you have set up the following:
(feel free to pause this recording at any time in order to make adjustments to your setup)
A sound-emitting source, such as a speaker. It should be placed at the same height as your ears. This is the source from which you should be listening to this recording.
Five markers of distance in a linear path away from the sound-emitting source. The distances of these markers should correspond to:
1.5 feet
3 feet
6 feet
12 feet
24 feet
These distances have been chosen, as they are easy measurements to make accurately utilizing a 25-foot tape measure, which should be easily accessible to most people in the United States. However, the same effect can be realized by measuring out any 5 distances in a linear path from the sound-emitting source which plays this recording, assuming that the same proportional distance is kept between each marker.
The Inverse Square Law states that as the distance between a listener and a sound-emitting source doubles, there will be a perceived negative difference of 6 decibels in the loudness of sound. In other words, the sound will be heard as 6 decibels quieter when the listener doubles their distance from the source of said sound. For example, a sound which is heard at 36 decibels from a distance of 5 meters, will be heard at 30 decibels from 10 meters away. If the distance doubles yet again, the same phenomenon occurs. Thus, that same sound would be heard at 24 decibels at a distance of 20 meters away. This very piece which you are now listening to is a sonification of this law.
At this moment, you should be standing at the first marker, which is 1.5 feet away from the sound-emitting source. Take notice of how loud the recording seems to you. Keep in mind that this piece is as much about your own perception of loudness as the listener, as it is about the theoretical principles of physics that pertain to this particular sonic phenomenon.
Now, take one step backwards to the second marker, which sits at a distance of 3 feet from the sound source, double the distance of the last marker. Take notice again of how loud the recording seems to you. At this point, you should notice that the sound appears to be the same volume to you as compared to from the previous marker. This is because the gain of the recording has been increased by 6 decibels to compensate for the perceived decrease in loudness due to your increased distance from the sound source.
Now, begin walking backward toward marker #3, which sits at 6 feet from the sound source. Once you arrive at this marker, you should again notice that it is the same perceived volume as compared to the previous marker, which is also the same perceived loudness as from marker #1.
Now, begin walking backwards toward the fourth marker, which sits at 12 feet from the sound source. As you do so, continue taking note of how loud this recording seems to you. Once arriving at marker #4, you should yet again notice that my voice is perceived at the same loudness as compared to from the previous 3 markers.
Finally, begin walking backwards toward the fifth marker. Again, continue taking note of how loud the recording seems while you are walking. The 6 decibel increase in gain has been automated in such a way that it attempts to create no perceived loudness difference, even during the process of walking between markers. However, the effectiveness of this approach may differ depending on your particular backwards-walking speed.
By now, you should have arrived at the fifth and final marker. For the last time, notice again that the perceived loudness from the distance of 24 feet appears to be the same loudness as from the previous 4 distances.
This piece has been a sonification of the Inverse Square Law."