Re: [Harp-L] was Embossing, now controvers
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From: David Payne <dave@xxxxxxxxxxxxxxxxxxxxxx>
Date: Sat, 29 Dec 2012 22:07:18
To: Harp L Harp L<harp-l@xxxxxxxxxx>
Reply-To: David Payne <dave@xxxxxxxxxxxxxxxxxxxxxx>
Subject: [Harp-L] was Embossing, now controversy
I would oppositely posit, as I'm sure you understand. Personally, I never found a need to try to deduce it with math, nor do I have the booklearnin' for it, I was an english and history major, you know. Although, I've got a good ear. I've never thought of it as an interaction of sound in moving air... in fact, that idea makes as little sense to me as it does to you. I believe it's about the reed and how it vibrates. What, I don't know, but the tonal change is from the reed itself. It is the reed itself and how air gets to it that is key. When airflow from the side is restricted there is a drop in treble overtone. It's there. I can hear the change. When altering this, I can hear a certain tone, then an addition of another tone and I can hear both those tones at the same time. To me, it's like if somebody saw a cat. He would say, "there is a cat." Then, a dog walked up next to this cat. Then, he would say "there is a dog next to this cat." To me, perception of those tones is no different than seeing dogs and cats. This airflow concept is not new. Of course, Brad explored it to great length with the B-radical, but it is way older. Richard Seydel Sr. was apparently the first to understand it and explore it in the 1890s. Most of the sound of a harmonica comes from this chopped column of air from the reed. Think of that as the cat. It's the base tone... the things I'm delving into are other tones that are additions to that base tone - the dog. Now, I will make some far more controversial statements myself that what Vern said and they will get more controversial as you read on. This isn't stuff I just thought up one day, it's from constant thinking and testing for years at the Elk River Institute for Advanced Harmonica Studies, I know it'll get picked to death, but this is stuff I've confirmed with repeatable tests. I seriously think about this stuff all day. It's very controversial and is dismissed by almost anybody - at least from what I've seen written - that is an authority on harmonicas. Ironically, it is the absolute easiest dynamic to confirm with a simple test. "The coverplate acts as a sounding board and works in a similar, although less significant way, as the top of a guitar."That's another old concept. The man who came up with that was Jacob Hohner and he designed a harmonica to take advantage of this dynamic - the mouse ear Marine Band. It's really simple to test. Grab a diatonic harmonica, hold it with a thumb on one end and a finger on the other end. Do not touch the coverplate in anyway. Blow any note (tonal changes seem to be easier to hear on blow notes). Then, take a finger and press it upon the top coverplate. Then release the finger. There is one tone that diminishes when you touch the coverplate and another that remains constant. When the finger is pressed upon the coverplate, there is a certain tone. That's the cat. Then, when the finger is released, there is a treble part of that tone that is increased. That's the dog. For those who do not think coverplates vibrate, blow a note (lower the better) and touch the top coverplate lightly against a tooth. You'll feel it. Now, blow that note and lightly touch the BOTTOM coverplate against another tooth. You don't need a tooth, you can feel it with a lightly-applied finger, but the tooth rattle is really obvious. It also vibrates. Again, when stuff vibrates, sound comes from it.Now, that largest surface of that bottom coverplate is, on the diatonic I just checked ( a Optimized session Steel), about 1.3 cm from the vibrating reed. Even the top coverplate is about 8 cm from the vibrating reed. Sound has to travel through a medium, be it solid, liquid or gas.Now sound waves traveling through air seem pretty weak to make all this coverplate vibration happen. That seems to be the case. This can be tested. Blow the same note with another harmonica 1.3 cm away (basically just get them as close as you can without touching). There is no perceptible vibration in the second harmonica's coverplate. Or, you could just lay a coverplate by itself down, whatever you want, there is no perceptible vibration. I have never found anything acoustically resonant whatsoever about a harmonica.So, the vibration in the coverplate doesn't come from the sound waves in the air. It travels through solid material to get to the coverplates.Sound travels differently through different solids. Go to your kitchen table and put your ear on it and rap your knuckles at arm's length, or better yet a ringing cell phone set to vibrate. Try the same with the countertop. Or the floor. A board. Whatever flat, solid surface you can find. The sounds, to your pressed ear sound different based on the material and construction of that flat surface. So, again, most of the sound from the reed doesn't get to the coverplates, it is traveling through a solid material to get there. What solid materials are there for it to travel through? Well, there's the reedplates and .... drum roll, please.... the COMB. By my theory here, metal combs would provide the best means of sound transmission. I - and there are people, some on this list, who can confirm - I can pick out a metal comb from another type on otherwise identical harmonicas even on the phone nearly 100 percent of the time. With wood vs. recessed reedplate plastic - I can pick out about 75 - 80 percent of the time. I think I could do better if I actually were to train myself. What I hear is an addition of treble tone with the wood, but it is very slight. Vern says people can't hear it. I think he's probably 95 percent right. But a difference exists and some people can hear it. There are ears far better than mine. With plastic vs. wood combs of the same construction - and the 1847 and 1847 Silver are the only ones I know of that are like this - I can tell hear no difference whatsoever. None. zilch, nada. But with metal vs. anything, it's a different story. There is a particular tone that is there with metal. I can only describe it as when a bell is rung, at almost the point where you can no longer hear it, but you can still kind of sense the vibration. I think that different vibration can also be felt. I'd like to know if that's true, or if I imagine it. I would like to test that sometime. I would need somebody to play a couple of harmonicas, one with a brass comb and one without while I've got earplugs in and see if I could tell a difference. That would be fun and I'd be interested to know how it turns out.
I am well aware this will get picked to death and I only ask that folks try some of these tests. Either each and every harmonica sounds exactly the same or they do not. It's one or the other and if they do not, I'm open testing out alternative suggestions. I might have tested them out already. Or maybe not. I've tested about everything I can think of on that subject... but there is a lot of stuff I've yet to explore, like what would a harmonica sound like if you blew helium into it and stuff. Haven't tried that yet.
________________________________ From: Vern <jevern@xxxxxxx>To: David Payne <dave@xxxxxxxxxxxxxxxxxxxxxx> Cc: Harp L Harp L <harp-l@xxxxxxxxxx> Sent: Saturday, December 29, 2012 7:01 PMSubject: Re: [Harp-L] Embossing and Compression (was Rick Epping, father of embossing) On Dec 28, 2012, at 8:54 PM, David Payne wrote:> "....... it seemed really obvious that ANY change in air flow changes the tone....."
It is not at all obvious to me. Your explanation doesn't fit with my understanding of harmonica aerodynamics and acoustics. You will find the following statement to be controversial. It is followed by a justification. I claim that when you discount your intuition and look at the problem quantitatively, a different picture emerges.
I posit that: "The flow of breath through the reed chamber and under the cover of a harmonica has no perceptible effect on the sound."
These are the reasons:
The velocity of sound is about 1125 feet/second.The cross sectional area of a 0.18 inch high x .18 inch wide diatonic reed chamber is about 0.032 square inches or .00023 square feet.The cross sectional area under the 0.16 inch high x 1 inch deep covers is 0.16 square inches or .0011 square feet. A player expels about 1 liter (0.035 cubic feet) of air in 8 seconds, a volume flow of about .0044 cubic feet per second.The velocity of breath through a reed chamber is about .0044 / .00023 = about 19 feet /second.The velocity of air under the cover is about .0044 / .0011 or 4 feet per second. IF the player does not hand-cup to completely block flow out the rear, then the velocity is even lower.4 ft/sec x 3600 sec/hr / 5280 ft/mile = 2.7 mph
Because the breath under the covers is moving at less than 1% ( 0.36 % ) of the speed of sound, there is little interaction. The behavior of sound waves in slowly moving air isn't very different from their behavior in still air.
Think of holding a conversation in a gentle 2.7 mph breeze.
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