Art Noxon, PE Acoustical is ASC’s founder & inventor of the TubeTrap. This week Art shares his perspective as he ‘reflects’ on the Hifi listeners’ journey. Enjoy!
The Wall In The Desert
By Art Noxon
An old saying is known in many countries “The chain is only as strong as its weakest link.” Often, when we talk about the parts in our audio system, they are referred to as components and interconnects in the audio chain. Each component processes the signal and the interconnects transfer the signal from one component to another. This is hopefully all for the better, resulting in quality sound arriving at our ears.
Modern audio equipment such as that found in any hi-end show or good dealer demo room is very accurate. Because this electronic equipment comprises most but not all parts of the audio chain, it cannot perform any better than the weakest link of the whole audio chain. We take a few minutes of time now to illustrate just how the final interconnect – the Room Acoustic – is not only one of the links in the audio chain, it is the last and the weakest link in the audio chain. What we do with this critical audio link will also be discussed.
Listening In the Desert
The story all begins because we are people who listen to sound. Imagine if we play a stereo in the quiet desert, the only sound we hear would be the direct sound from the speakers. No reflections, no noise, nothing to complicate what we hear. This would be an anechoic space, one without echo or reflection.
Let us imagine further that we next position ourselves in the vicinity of a large stone wall, located far behind, crossing from back left to right. Sound from the speaker will first pass by us, traverse a long distance and then reflect off the wall. However, this wall is too far away and we do not hear its reflection. Because of the distance, the sound takes a long time to return to us and also it grows very weak – too weak to be heard.
Next we imagine relocating our stereo system closer to the wall. The reflection arrives more quickly than before and it is louder, so this time we hear an echo. Once again we relocate even closer to the wall and the time delay for the echo becomes smaller while the strength of the echo grows stronger.
We can move even closer to the wall and at about 10 meters the distinct quality of a separate echo begins to disappear even though the reflection is stronger than ever before. And by 8 meters distance the echo effect has completely disappeared. The wall reflection is without doubt quite loud but it is no longer clearly heard as an echo. This reflection follows the direct signal so close in time that our ear-brain system fuses the two separate sounds into one single sound and we now have realized the “sound fusion” effect. Those reflections that shortly follow the direct signal will blend into and become part of the direct signal itself. It is a natural feature of the hearing process.
Listening In The Room
Next, we relocate our thought experiment into a more conventional setting, your HiFi listening room. The room has four walls, a floor and a ceiling. Six reflecting surfaces means there are six times the number of initial reflections than when we listened with our back to the stone wall. After these first six, early reflections pass by there develops a sequence of reflections that rapidly become very complicated. This is because each reflection rebounds across the room only to meet another wall and be reflected again, then again and again.
If the room is big, the reflections are sufficiently time delayed so that we hear the echo of the room. This echo is often not one simple echo but many echoes arriving in a confused manner, randomly scattered over time. If the room is small, the reflections are not time-delayed sufficiently for us to hear the room as a separate echo. We do hear small room reflections quite loudly, we just do not recognize the reflections as a separate sound. It is only because we do not consciously recognize the reflections in the small room as a distinct acoustic signal that we tend to forget that they compose the majority of the sound we hear. The speaker is the last component in the audio chain and the room acoustic is the last interconnect. Distortions in any of the interconnects, including the last one will degrade the quality of the audio signal.
The Acoustic Interconnect
Long time delay reflections, echoes are very bad for good listening. But what about the short time delay reflections, those that belong to the listening room? In some ways they are actually good for listening but in other ways they become a hindrance. Because of sound fusion, the early reflections add to the direct sound and make it seem louder than it actually is. For conversational speaking this is a benefit. However, in audio we don’t actually need the help of room reflections to make loud sound, we have the amplifier and speakers to deliver sound power.
Most people do not own listening rooms large enough to have an echo. We also do not own rooms that are completely without reflections. Hifi listening rooms have many reflections, most of which fall within the 1/20 second sound fusion period of time. So we always hear the room right along with the speaker. This is why the audio experts always say that the room is part of the audio chain. The Room Acoustic interconnect is not only the last link in the audio chain. With the high quality of today’s audio electronic components and interconnects, the Room Acoustic has certainly become the weakest link, and because of sound fusion in small sized listening rooms, the Room Acoustic is the most forgotten link in the audio chain.
Sometimes it is hard to remember that the room is an interconnect because we are so used to interconnects as being cables with plugs that we buy at the HiFi shop and take home in a box. The sound we hear is due to the combination of all the purchased electronic components and electronic interconnects plus the existing distortion and confusion from the last interconnect, the room acoustic. Curiously, people in audio often upgrade their electronic interconnects long before they even think of improving their acoustic interconnect.
What can we expect from our room? It is simply no more than one of the rooms that came with the house. It may even be a nice room but it was never built to be a distortion free wave guide for hi end audio signals, it was built for eating, sleeping or visiting. Hi end audio needs something more than a simple, contractor built room to be in control of the last interconnect in an otherwise quality audio chain.