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Steve A Heavyweight Member
Joined: 26 May 2006 Posts: 1808 Location: Toronto, Canada
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Posted: Tue Jan 12, 2021 3:48 pm Post subject: 100 Ohms of Resistance? |
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DISCLAIMER: I realize that this understanding isn't required for playing the trumpet well. If you think this is a waste of time, please feel free to ignore it, rather than arguing against trying to learn or understand. Thanks!
Possibly opening a can of worms, but in hopes of learning something, here it is:
In this video, KO Skinsnes of Stomvi says there's debate about whether or not lips start closed, or open and act in response to 100 ohms of acoustic resistance to start the buzz cycle:
https://www.youtube.com/watch?v=bdDTVdYOXNQ
I understand the cycle when starting from closed lips. Can anyone explain in layman's terms what the 100 ohms model would entail?
Thanks! |
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Tpt_Guy Heavyweight Member
Joined: 16 Jul 2004 Posts: 1101 Location: Sacramento, Ca
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Posted: Tue Jan 12, 2021 4:40 pm Post subject: |
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100 ohms?
If acoustical resistance is measured in ohms then I would think playing trumpet would be rather shocking!
Sorry to be a bit of a joker. The ohm is the SI unit of measurement of electrical resistance; I couldn't find any use of ohms to measure any other resistance.
He may be trying to use it as an analogy, but using ohms to measure something nonelectrical seems a bit discrediting. _________________ -Tom Hall-
"A good teacher protects his pupils from his own influence."
-Bruce Lee |
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cheiden Heavyweight Member
Joined: 28 Sep 2004 Posts: 8911 Location: Orange County, CA
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Posted: Tue Jan 12, 2021 4:46 pm Post subject: |
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Not exactly laymen's terms but might help some...
https://www.animations.physics.unsw.edu.au/jw/sound-impedance-intensity.htm _________________ "I'm an engineer, which means I think I know a whole bunch of stuff I really don't."
Charles J Heiden/So Cal
Bach Strad 180ML43*/43 Bb/Yamaha 731 Flugel/Benge 1X C/Kanstul 920 Picc/Conn 80A Cornet
Bach 3C rim on 1.5C underpart |
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kalijah Heavyweight Member
Joined: 06 Nov 2003 Posts: 3257 Location: Alabama
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Posted: Tue Jan 12, 2021 5:41 pm Post subject: |
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Quote: |
He may be trying to use it as an analogy, but using ohms to measure something nonelectrical seems a bit discrediting.
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Acoustic ohm is defined as:
Pascal x second/cubic meter |
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kalijah Heavyweight Member
Joined: 06 Nov 2003 Posts: 3257 Location: Alabama
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Posted: Tue Jan 12, 2021 6:06 pm Post subject: |
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In the video, when he referred to 100 ohms he was describing the resistance of closed lips.
However, the resistance of closed lips is infinite as there is zero flow. |
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Tpt_Guy Heavyweight Member
Joined: 16 Jul 2004 Posts: 1101 Location: Sacramento, Ca
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Posted: Tue Jan 12, 2021 9:26 pm Post subject: |
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kalijah wrote: | Quote: |
He may be trying to use it as an analogy, but using ohms to measure something nonelectrical seems a bit discrediting.
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Acoustic ohm is defined as:
Pascal x second/cubic meter |
Learn something new every day, sort of.
I see on the link from cheiden Z [impedance] = p [pressure]/U [flow] - brackets are for clarification and not part of the forumla. Math isn't my strong suit. How does that relate to the formula you posted? _________________ -Tom Hall-
"A good teacher protects his pupils from his own influence."
-Bruce Lee |
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kalijah Heavyweight Member
Joined: 06 Nov 2003 Posts: 3257 Location: Alabama
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Posted: Wed Jan 13, 2021 3:52 am Post subject: |
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Pascal = pressure
Flow=cubic meters/ second
Impedance = pressure/flow = Pascal/(cubic meter/sec)
= (sec/cubic meter)x Pascal = Pascal × sec/cubic meter |
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Steve A Heavyweight Member
Joined: 26 May 2006 Posts: 1808 Location: Toronto, Canada
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Posted: Wed Jan 13, 2021 11:37 am Post subject: |
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All right, I'll be honest, I'm not sure I'm understanding this any more than I was to start with, but that's probably a reflection of me more than anything else. Thanks, all. |
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Crazy Finn Heavyweight Member
Joined: 27 Dec 2001 Posts: 8333 Location: Twin Cities, Minnesota
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Posted: Wed Jan 13, 2021 12:32 pm Post subject: |
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There seems to a discrepancy in understanding what “layman’s terms” actually constitutes.
Lol. _________________ LA Benge 3X Bb Trumpet
Selmer Radial Bb Trumpet
Yamaha 6335S Bb Trumpet
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Bach 184L Bb Cornet
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deleted_user_687c31b New Member
Joined: 03 Apr 1996 Posts: 0
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Posted: Wed Jan 13, 2021 1:05 pm Post subject: |
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kalijah wrote: | In the video, when he referred to 100 ohms he was describing the resistance of closed lips.
However, the resistance of closed lips is infinite as there is zero flow. |
I suppose that's mathematically true, but the moment you start exhaling there will be an airflow (unless you manage to squeeze your lips really tight, but even then the airflow usually wins out eventually). I guess their description isn't 100% accurate in this case, as the flow automatically means there'll be a gap between the lips, but for a non-phycisist it'll be easier to understand that the lips start 'closed', even if they technically open as soon as the flow starts. |
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kalijah Heavyweight Member
Joined: 06 Nov 2003 Posts: 3257 Location: Alabama
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Posted: Wed Jan 13, 2021 1:27 pm Post subject: |
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If the pressure is sufficient to push the lips open, that will occur and flow will begin. And there will then be a finite resistance.
When playing a tone, both the lip aperture AND the instrument resistance contribute to the total resistance. The total (average) resistance is then the air lung pressure divided by the average flow. |
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BraeGrimes Veteran Member
Joined: 14 Apr 2011 Posts: 269 Location: Australia
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Posted: Wed Jan 13, 2021 4:41 pm Post subject: |
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This is super interesting. Thanks for sharing. You're right in that there would be a little paralysis by analysis here, but still very interesting to see trumpet physics. I'm guessing they get this Ohm resistance figure by calculating the time it would take to reflect back in conjunction with the cubic area (maybe including the cavity of the mouth?). I'm no scientist! Super cool |
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Lionel Heavyweight Member
Joined: 25 Jul 2016 Posts: 783
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Posted: Wed Jan 13, 2021 4:43 pm Post subject: |
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kalijah wrote: | In the video, when he referred to 100 ohms he was describing the resistance of closed lips.
However, the resistance of closed lips is infinite as there is zero flow. |
You forgot one thing Darryl (lol)! it isn't necessary but it is interesting. Here goes:
While playing your trumpet or any brass instrument for that matter the horn doesn't care which direction through the pipes that the air flows. Although this can create a difficult and kinda yucky condition. That is when you consider all the scum that eventually resides within the brass tubing of an instrument. Then follow that up concept up by just thinking of all that gunk meanwhile drawing IN the air towards the mouthpiece. Also, you'll need a set of chops that works backwards as well as forward too. So this will eliminate a number of players who roll in the lower lip and point the horn angle downwards. The air just doesn't like taking that path through your lips while trying to maintain a playable tone. This channel creates way too much resistance to REVERSE the airflow when using the breathing and mouth apparatus that never was designed to allow a backwards flow of air.
In fact you can prove this to yourself another way too. Perhaps all of us have seen that clever Youtube trumpet player who promises "everyone a solid G above high C within just a couple of minutes". This is the guy who removes the squeaker reed assembly from a little kid's bathroom toy. He carefully attaches it inside his third valve slide. Because the third valve is much less used than the other two he can now make it SEEM like he's actually playing an ascending run-up to G/High C. Only when he reaches the point where he needs to play the High G?
He merely presses down the third valve and blows like Hell into the horn without buzzing his lips. It's funny as can be. However the exact same high note can be sustained easily by drawing IN the air while pressing down the third valve.
Another thing I've noticed is that despite the mechanical advantage the toy squeaker element provides, the quality of the G/High C can sometimes run a little thin. Just as some trumpet players who can blow G/High C and yet not get a truly big sound. _________________ "Check me if I'm wrong Sandy but if I kill all the golfers they're gonna lock me up & throw away the key"!
Carl Spackler (aka Bill Murray, 1980). |
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