The 5.1 sound system – part 3

My home stereo system has 6 speakers – I counted them!  Yet, this set up is called a 5.1 sound system.  What’s going on?

My first thought was that the guy who installed it couldn’t count.  My next thought was that the manufacturer really wanted to call it 6.1 or at least 6.0, but certainly not something that sounded less than it actually was.  Of course, this was before I studied audiology and didn’t know the different characteristics of sounds.

Well, a 5.1 sound system is really what it is, and here is why…and please forgive me Edwin Abbott who wrote the wonderful book Flatland…I am about to copy you! Actually this is a great book once you get over the misogyny that was characteristic of the late 19th century.

Once upon a time there was the land of Sound.  There were two types of inhabitants- the Lows and the Highs.  Quite understandably they were kept apart and really there was no reason for them to mix.  I recall that at one time, a low wanted to marry a high but everyone thought that relationship was unsound from the very beginning- what do they have in common?  What schools would their kids go to?  Could they even have kids together?

But let’s take a step back…

I happened to live just down the street from a family of Lows.  They were without direction in life; they carried very little information and were thought to just be, without any reason for being; and unfortunately for many, they were everywhere.  I personally think that the Lows were just too stupid to know that they were simply not wanted.

In contrast, the Highs were very driven with sometimes a singular direction; they were the smart ones and could clarify anything, and unlike the Lows, they didn’t travel very far.  And oh yes, the Highs died young- they started to leave us when just in their 60s.  The Lows seem to go on forever- I guess that’s the price for being too smart and carrying too much information.

And what a coincidence that the behavior of Lows and the Highs are identical to the behavior of low frequency sounds and high frequency sounds!!

Low frequency sounds, because of their long wavelengths do not see walls or people as obstructions and tend not to reflect or refract around them.  A speaker- human or loudspeaker- if aimed in one direction, will have almost the same sound level if measured from behind.  In contrast, high frequency sounds, due to their shorter wavelengths, tend to be very directional, and the very high frequencies can be aimed almost like a laser beam (as in the commercially available Hypersound technology).

So, my 6 speaker system does indeed have 6 speakers, but the subwoofer (that’s the large one) can be aimed in any direction, including the wall, and be placed under or behind my couch, and still provide plenty of bass response.  Bass is simply not directional, so advertising this system as being 6.0 or 6.1 would be false advertising since there are only sounds emanating from 5 distinct directions.  The “.1” number in 5.1 merely refers to the non-directional low frequency woofer.

 

 

About Marshall Chasin

Marshall Chasin, AuD, is a clinical and research audiologist who has a special interest in the prevention of hearing loss for musicians, as well as the treatment of those who have hearing loss. I have other special interests such as clarinet and karate, but those may come out in the blog over time.