Submit the best reason for this to happen and win a Free Trumpet Ensemble Arrangement Of Your Choice!
Selection of best reason will be made on June 1, 2014.
Submit the best reason for this to happen and win a Free Trumpet Ensemble Arrangement Of Your Choice!
Selection of best reason will be made on June 1, 2014.
Immersing the bell in the water compresses the air in the air column, changing the frequency of vibration to a half-step higher. There is a finite leak from the valves, and what does not leak bubbles out. More slowly and in larger volumes as the horn is more deeply immersed. But the pressure within the system remains at equilibrium, the air seeking the path of least resistance out of the horn.
Whow! I’ll have to take this statement by statement.
1. Immersing the bell in the water compresses the air in the air column, (I assume you mean “as a note is played” the air is compressed)) changing the frequency of vibration to a half-step higher.
Sorry, this is not the answer.
2. There is a finite leak from the valves, and what does not leak bubbles out. More slowly and in larger volumes as the horn is more deeply immersed. (I’m not sure what you mean)
3. But the pressure within the system remains at equilibrium, the air seeking the path of least resistance out of the horn.
Your reference to “equilibrium” is getting close to the answer but sorry, this is not the answer.
Since water is denser than air, the sound waves travel more efficiently and at a higher rate of speed through water, which results in a raised pitch.
Again, thank you for your attempt but the answer again is much more simple.
Sound travels faster in water than it does in air, raising the pitch of the notes. You would get the same result if you placed a speaker underwater.
Thank you for your solution but unfortunately the answer is much more simple to explain.
The behaviour of trumpet in the video is due to varying damping in an acoustic oscillator.
Playing in water which is impedance-mismatched with the trumpet air column causes reflection of most sound waves back into the bell; sound escaping to the outside is weaker, damping is weaker, pitch is higher.
When played in the air, the impedances of surrounding air and trumpet air column are matched by the bell; sound reflected back to the bell is weaker; sound escaping to the outside is stronger, damping is stronger, pitch is lower.
The difference between two scenarios is not major as evidenced by the pitch shifting only by one semitone. This is because most of the sound, even in the air, is reflected back into the trumpet air column.
The larger part of the bell reproduces the lower spectrum of a trumpet’s sound, by immersing it in water, this lower spectrum is diminished and the pitch increases.
The water acts like a mute. Put a mute in, the horn goes sharp.
One the trumpet is in the water, the trumpet, water and sink are now an integrated unit. The trumpet is transmitting vibrations through the water to the aluminum sink, which is also resonating. That part is constant whether bring the bell up or down. You are basically playing the aluminum sink through your trumpet.
The water acts as a *stop* mute.
This is true but why does the transposition remain the same as the bell is lowered into the water?
Putting the bell in the water changes the resonance equation from that of an open tube (f=(nv/(2(L+0.8d))), all positive integer harmonics) to that of a closed tube (f=(nv/(4(L+0.4d))), positive odd harmonics only). And no, I couldn’t just remember those equations from college, but they weren’t hard to find (http://en.wikipedia.org/wiki/Acoustic_resonance). As the air you’re blowing through the horn bubbles out (thereby venting the closed tube), the water level inside the bell stays constant, so the “L” in the equation doesn’t change.
Notice how your tone sortof breaks up as the pitch changes? That’s because the pitch is actually at the next harmonic flattened to a half-step above the original note. (See http://www.public.asu.edu/~jqerics/ess_play.htm.)
Sounds move faster through a denser medium. Water is denser than air so the sound moves faster thus raising the frequency.
Sound traveling through liquid travels faster than in air. Properties stay the same no matter how deep you are in the water.
I have no answer, but a few questions.
First, did anyone else notice at the moment the bell hit the water, the pitch actually dropped about a half-step, before it raised a half-step from the original pitch? Why?
Second, try this: blow air (no buzz) through the mouthpiece into an open horn and listen to the pitch. Next, lightly tap the palm of your hand on the mouthpiece (with no valves down) and listen to the pitch. They are different. Why?
Excellent observations!
Once we have established the winner in this contest (June 1) we need to address your comments.
Thanks for adding more questions to this exercise.
Be well and live long.
The first question is answered above:
“Notice how your tone sortof breaks up as the pitch changes? That’s because the pitch is actually at the next harmonic flattened to a half-step above the original note. (See http://www.public.asu.edu/~jqerics/ess_play.htm.)”
The phenomena addressed in the second question is due to the manner in which energy is added to the acoustic system. When you blow air (no buzz) through the horn the system reaches critical damping (I think that’s what it’s called — I don’t want to say how long ago college was but Ronald Reagan was president) and the principal resonations occur at the fundamental frequency. When you “smack” the mouthpiece you excite the acoustic system with a multitude of high frequencies for a very short time. Resonations occur at many higher harmonics and decay rapidly, causing you to hear a higher pitched “pop.”
You have surely added class to this web site.
It’s going to take me most of the week to check out what you said.
Thanks for challenging the older generation to think….
I believe that it is because you are changing the medium in which the vibrations are going through, altering the frequency given off.
While playing open air, the last few centimeters of the bell flare do not contribute to the resonant length of the trumpet. But playing underwater, the air column is slightly longer because it includes the bubbles path up to the border of the bell.