How we hear sound
Psychoacoustics. It conjures up visions of Sigmund Freud but it's really just about how we all perceive sound. The reality is that, like all our senses, there are few hard and fast truths. We are interpreting our external experiences. Each of us will interpret the same event slightly different. If Einstein is to be believed, we all inhabit our own time but let's not go there...Instead let's start by pointing out just what an incredible auditory system the human ear actually is: the ear can hear sounds in the range of 20Hz to 20kHz. The upper range is actually about the point we start doing permanent damage to our hearing. Put that another way, the ratio between the faintest sound we can detect and the loudest sound we can hear without damage is 1 trillion to 1.
Our hearing changes with ageAs we get older we begin to lose the lower end of this range which means that children will be more affected by bass sounds while older people will be more affected by treble. In either case, we have a very dynamic auditory range of perceiving sound intensity. So, what we consider 'too loud' or 'too much bass' will be determined by our own sound perception.
That's a big problem for the audio component of a home cinema system. When you come to place your speakers to get the ideal surround experience, you need to understand the psychoacoustic phenomena involved – and be able to make adjustments for them.
Poorly arranged surround sound may not just be annoying, it has been known to frighten some people. People are simply not expecting or prepared for imminent and strong sound coming from behind them. You could very well give your aging grandmother the heebee geebees, and no one wants that!
This is, thankfully, an extreme example. More likely, the audio will sound 'unnatural'. It is being transmitted in a way or at a frequency that the ear isn't used to. It will be both unpleasant and confusing.
Our senses want to do just that. They want to make sense of the world for us. Even when the sound is wrong, our brain will try to make sense of it for us. The issue lies in the localization of the sound.
Making sense of sound
We make sense of any sound by interpreting the sound we hear in both the left and right ear. The brain accepts the stimuli from the ears and uses the differential in time, volume and frequency between the two inputs to create a stereo picture that places the sound in terms of the type of sound, its direction and its proximity.
When we're creating an audio set-up for home cinema, we need to be able to recreate a localization of sound in a way that is natural to the listener. It means placing and optimizing speakers so that any coloration (the effect a subsidiary noise can have on the main sound event) of the sound helps the localization process. It means having the ability to separate the sound channels and play them through the correct speakers. We need to be able to introduce tiny delays so that sounds are issued from the speakers at exactly the right time.
If you can achieve this properly then you have the potential to really enhance the listening experience. The greater amount of localization that you are able to achieve, the more natural and transparent the sound. The ear will be able to pick up the sounds you want and be able to place them instantly where they should be. As surround sound always promised, the listener is enveloped in the sound. We've become immersed in the action. The whole experience is heightened but in a way that we accept and welcome.
Designed with the brain in mind
The people behind the leading audio processors have been building systems that aid psychoacoustics for many years. Most have advanced features that allow you to move above simple technology tuning to accommodate the way we perceive sound and the type of sound that we, as individuals, prefer. Sophisticated room optimization techniques help as does granular speaker control.
The result should be to create a set up where the room is tuned and the speakers arranged to deliver the greatest listening 'sweet spot'. The area in the room where you get the most natural, localized sound perception.
Datasat Digital Entertainment has developed the RS20i on the same audio processing technology that we have used to bring this level of listening experience to cinema theaters. It includes a wide range of functionality that allows for sound correction based on the individual preferences of the listener.
In the end, there's no such thing as the perfect sound. There's only the sound we individually like to hear. The home cinema audio processor you choose should understand that.