I'm constantly amazed by the things folks knew about hundreds or thousands of years ago. This is especially true when that knowledge was lost in the mists of time, and we're only just now beginning to rediscover it.
As an example, consider the humble bell (the sort of thing you find in a church tower, for example). We're used to bells that – when struck – vibrate with one major tone (plus lots of interesting harmonics) that gradually fades away. The key point here is that we expect to hear the same fundamental tone, irrespective of where we strike the little rapscallion.
But is this always the case? Actually, the answer is a resounding "No!" (again, with lots of interesting harmonics). Apparently two-tone bells were common in China between 1200 and 200 BC. These little scamps have an eye-shaped cross-section and can vibrate in one of two modes depending on where you hit them. If you do it right, you can get both tones simultaneously, each with its own fundamental and harmonics.
Amazingly enough, a fully preserved set of 65 bells (with 130 tones) was discovered in 1978. These were found in the tomb of the Marquis Yi of Zeng in the Chinese province of Hubei and have been dated from 433 BC.
Way Cool! If you are interested, you can find out more details on these little rascals at the Zeng Bells website. I want a set!
Questions? Comments? Feel free to email me – Clive "Max" Maxfield – at firstname.lastname@example.org). And, of course, if you haven't already done so, don't forget to Sign Up for our weekly Programmable Logic DesignLine Newsletter.