Apples and Oranges

I must say, as soon as I saw¬†‘The Biology of Home Entertainment‘ tweeted, I thought I’d be reading something interesting. It promised to explain ‘How your senses influence your level of enjoyment!’

That makes a great deal of sense. The article itself makes very little sense.

In fact, its main point is profoundly silly. It gives a little discussion on the development of the visual and auditory senses in humans, and notes that with a field of view of 170 degrees vertically, and 200 degrees horizontally (including peripheral vision), the total human field of view is about 40% of what’s out there. It then goes on:

… we can easily appreciate that our visual cues make approximately 40% of the information we have going on around us, the balance of which comes from the auditory cues.

Knowing that our field of view is approximately 40% then it would stand to reason to allocate 40% of our budget to the vision products we need for our home theatre, thus giving the remaining 60% to the audio system. Now if we investigate further this ratio begins to look not just sensible but more like a light globe moment.

No, this is not a light globe moment. It is not in the least bit sensible. It is just plain silly.

First, and most trivially (it was just an afterthought to check the mathematics), assuming that the 170 and 200 degree angles hold all the way out, then the maximum field of view is only 26%, not 40%! (Check for yourself: 170/360 x 200/360.) If the corners of the field of view are rounded, then it is even less.

Second, and equally trivially, even if it were 40%, the article goes on to note that sound is encompassing, in effect having a 100% ‘field of view’. So the split shouldn’t be 40/60, but 40/100.

Finally — and now we’re getting to my real objection — what has field of view got to do with importance? Um, nothing whatsoever. I was about to mount an argument for this, but it is so monumentally self-evident, I couldn’t be bothered. So let me just say vision is an orange, and audio is an apple. Together they make a nice fruit salad, but they cannot be compared or apportioned on the same criteria as each other.

Having made that apportionment, the piece assumes that a 40/60 in the real world somehow maps onto your budget 40/60. What a strange assumption! It would only hold true if the¬†performance/cost ratio is the same for audio and video gear, but that is plainly wrong. In fact, you can get very close to perfection (in the sense of delivering the picture on the disc) in video for under $10,000, and still be quite a way off perfection (in the sense of delivering an accurate representation of the sound on the disc) for over $20,000. The article’s inane ratio understates the importance of high quality audio gear.

But, in any case, the balance has got to be a personal one. If you love movies above all else, and your total budget is under $10,000, I’d suggest you lean towards the video quality side of things. If your foremost love is for music, then lean towards the audio side and make do with a lesser picture.

To finish off, there is a table in the piece which is wrong. It says that the human ear can detect sounds with frequencies which range up to a 1,000:1 ratio, but that a good microphone can only manage 20:1. 20:1! Bloody hell, that’s what the carbon granule ‘microphone’ in an old-fashioned telephone receiver can manage (say, 200 to 4,000 hertz). A good quality microphone can manage 1,000:1 (20 to 20,000 hertz), and a really good one can go even beyond that. In fact, I’d suggest that the range of operation of a good quality microphone exceeds that of most human ears, and certainly the average, and that their linearity is very much greater. (See the Fletcher-Munson curves to see what a crappy frequency response the human ear actually has).

The table also claims that the human ear has a strong to weak signal range of 32 trillion to one, compared to a mere million to one for the microphone. Those figures look pretty amazing, and they are. But I’d just note that, expressed more conventionally, they are 135dB for the ear and 60dB for the microphone. I’d be surprised if a high quality microphone didn’t have a greater dynamic range than that.

Update (2 Feb 2011): Incredible! Treblid has sleuthed out that the author of the piece seems to have lifted the table wholly from elsewhere, and that it doesn’t actually purport to say anything at all about microphones. The ‘ECM’ referred to is actually ‘Electronic Counter Measures’. See here and here.

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