Dampening by air cushion only

larryace

"Uncle Larry"
So OK no deputization ceremony and NO GUN FOR YOU! (said like the Soup Nazi)

I think I'll go and dampen my sorrows over this turn of events.
 

someguy01

Well-known member
damp·ing
/ˈdampiNG/

noun


  1. TECHNICAL
    a decrease in the amplitude of an oscillation as a result of energy being drained from the system to overcome frictional or other resistive forces.

    I would say Larry is correct from the actual technical aspect of what is being discussed as it is related to pitch.
 

GetAgrippa

Platinum Member
No no Larry you're right when you "dampen one's spirit or enthusiasm" it's like putting a "wet blanket' on it. People "flood" the person with negativity so they "drown" in it. People often "cry"from the dampening which is salty like the sea or people get mad as "wet hen". I think the counter arguments are a "wet squib"-so even the arguments are "wet./damp" and don't even get off the ground.
Yep what better to dampen a fire than water. I always spit on my hands, drum sticks, and drum heads to lubricate everything as all good and great drummers do-this a direct quote from the Drummer's book of Secrets (way better than the President's Book of Secrets) and also referenced in the Drummer's Bible-so like drumming scripture. Hee,hee,hee.
 

MrInsanePolack

Platinum Member
This is part of altering the resonance but I don't see how it would change the pitch.
If something is removing certain frequencies but allowing other through, this would change the soundwaves that reach our ear and thus change the pitch?

This is a poor example, but hear me out. Say the drum is producing 50% high frequencies and 50% low. If the damper is catching 50% of the high frequencies, your ear is now receiving half the highs and all the lows. In essence, your ear was receiving a 1:1 high/low mix, and now your ear is receiving a 1:2 high/low mix. I would imagine this has something to do with the change in pitch.
 

Supergrobi

Technical Supervisor
OMG it's damping not dampening! You guys are killing me!
Actually there's both imho: [1] [2] [3]

But nonetheless - thanks a lot! As a non-native speaker I'm always happy if someone points out my mistakes so I'm able to improve. I haven't had too many English lessons in school so for me it's learning by reading/listening/speaking.

I forget the details, but think in terms of how the wavelengths of various sound wave frequencies affects their absorption.
Sorry, I don't understand what you mean in this context.

Probably with just a 2 mm rise the vibrating head sporadically does touch the head
Good point, although it worked with the bare hand, too, so I was able to ensure the head wasn't touching my hand while vibrating.

reflected waves stifle the head at that point changing the whole dynamic of head vibration.
Which would happen because of air pressure between the head and the dampener, reducing the ability to vibrate, my current guess what's going on there.

I wonder if just adding mass to the rim is changing it? Like adding hardware does.
Also good point, I'll test this by mounting it facing away from the drum. But it wouldn't explain the effect using my hand with nothing mounted to the hoop.

I'm guessing it took some ring out of the hoop. It would dampen the hoops vibration. The sound would be affected.
You also have a point, will test it like outlined above. But this also wouldn't explain the effect with the hand.

Seems this is something to be looked into a bit more. ATM I'm very busy with continuing construction of my studio complex but afterwards I guess I'll sit down a Sunday afternoon, doing some more testing and maybe recording of the results. Things to be tested (to be continued):

  • Effect on the reso head
  • Mount the dampener facing a) towards and b) away from the drum for two tests:
    • Lowering the pitch by adding mass to the hoop (and so the overall system)
    • Lowering the resonance by dampen the hoops vibration
  • Other materials to test:
    • Wood
    • Metal
    • Ceramic/glass
    • Absorber foam
 

larryace

"Uncle Larry"
Super...I have to think that the examples you provided were examples of the wrong usage of that word. I don't know for sure, that's a guess. But I do suspect it

I see the wrong usage of that word EVERYWHERE
 

Otto

Platinum Member
A head does move more than 2 mm when struck to reach the maximal travel due to oscillation.

I was surprised when I started experimenting with keeping the stick on the head just how far the batter travels after being struck...though it only stays in that range of amplitude for a short period.

Hold a stick close to the batter braced on the rim...then strike the batter with the other stick...move the braced stick up very little at a time until you no longer get contact between the braced stick and the head...its much further than I remember thinking it would be.(depending on tuning of course)
 

Supergrobi

Technical Supervisor
If something is removing certain frequencies but allowing other through, this would change the soundwaves that reach our ear and thus change the pitch?

This is a poor example, but hear me out. Say the drum is producing 50% high frequencies and 50% low. If the damper is catching 50% of the high frequencies, your ear is now receiving half the highs and all the lows. In essence, your ear was receiving a 1:1 high/low mix, and now your ear is receiving a 1:2 high/low mix. I would imagine this has something to do with the change in pitch.
A (poor) illustration: let's imagine we have a snare drum covering the following spectrum

resp1.png

Raising the lows, reducing the heights would look like:

resp2.png

Change in pitch would look like:

resp3.png

I exported a short audio clip of my snare drum (WAV 16bit/48kHz), adding effects as shown above.
 

Attachments

  • Snare.zip
    438.1 KB · Views: 0

wildbill

Platinum Member
....Sorry, I don't understand what you mean in this context.....
I don't either :ROFLMAO:

It's complicated. Probably a good area for GetAgrippa to explore.

It's been a long time since I had any acoustics classes, but I was thinking in terms of sound absorption and reflection.
What you described sounds like a miniature example of what's done in prepping a room to use as a studio.
Essentially, a small baffle is absorbing and reflecting different frequencies.
Also the position of the baffle, the drum, and your head will affect binaural perception.

Maybe someone else can dig into it. Here's a couple for starters:

Of course, the second link is referring to mics, but if you disregard the electronic aspect,
the purely physical aspect of a block/baffle might have a similar effect on frequencies.

Also - this probably doesn't come into play here, but in an open area - think outdoor concert,
high frequencies disperse much more quickly than the lows.
 
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Supergrobi

Technical Supervisor
Super...I have to think that the examples you provided were examples of the wrong usage of that word. I don't know for sure, that's a guess. But I do suspect it

I see the wrong usage of that word EVERYWHERE
Well, in this case all translation services I'm aware of are using the wrong version then. It wouldn't be helpful to post links since there's not too many German speakers here I guess. But in German dampening/damping basically is "Dämpfung" (reducing vibration of whatever) compared to "Durchfeuchtung" (making things wet). My go-to translators offer things like:
  • cost dampening
  • dampening effect
  • vibration dampening
However. Me derailing my own thread is a new quality to me :)
 
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MrInsanePolack

Platinum Member
A (poor) illustration
My poor illustration is more what I'm talking about. Keep in mind I'm just thinking out loud, not disagreeing:

20211021_112053.jpg

I'm fully aware that this is not how a drum works. I'm only suggesting that maybe the damper blocks certain frequencies while allowing others to pass through, thus allowing for the change in pitch you observe.
 

Supergrobi

Technical Supervisor
I don't either :ROFLMAO:

It's complicated. Probably a good area for GetAgrippa to explore.

It's been a long time since I had any acoustics classes, but I was thinking in terms of sound absorption and reflection.
What you described sounds like a miniature example of what's done in prepping a room to use as a studio.
Essentially, a small baffle is absorbing and reflecting different frequencies.
Also the position of the baffle, the drum, and your head will affect binaural perception.

Maybe someone else can dig into it. Here's a couple for starters:

Of course, the second link is referring to mics, but if you disregard the electronic aspect,
the purely physical aspect of a block/baffle might have a similar effect on frequencies.
What you're describing in terms of sound absorption is somewhat related, since the Gibraltar thingy also reduced the resonance of the drum. But it has nothing to do with changes in pitch.

Proximity effect is happening when the microphone is very close to the source. Science is still a bit undecided about the reasons, some say it has to do with the curvature of the sound front close to the source, so the diaphragm is exposed to a relatively huge path difference within the curved wave front, others say it depends on acoustic particle velocity and sound pressure level being out of phase by 90° close to the source of sound.
 

Supergrobi

Technical Supervisor
My poor illustration is more what I'm talking about. Keep in mind I'm just thinking out loud, not disagreeing:
Thanks for the drawing and for wrapping your head around it! What has to happen in order to change the pitch is that the waves you draw are somewhat elongated. To rely on your drawing maybe like this (blue: original, pink: lowered pitch):

drum.png
 

MrInsanePolack

Platinum Member
Thanks for the drawing and for wrapping your head around it! What has to happen in order to change the pitch is that the waves you draw are somewhat elongated. To rely on your drawing maybe like this (blue: original, pink: lowered pitch):

View attachment 109581
Oh, I see what you are saying. I'm out of ideas then, as its not moving so it isnt the doppler effect, and I dont think reflection can change the wavelength.
 

Otto

Platinum Member
I think the damper IS actually coming into contact with the head as the head oscillates...causing a frequency range change produced by the drum when the damper diffuses the highest peaks the drum attempts to express.

Damped Harmonic Motion I think we are referring to...and slightly wetting the head also describes much the same way : )
 

Supergrobi

Technical Supervisor
I think the damper IS actually coming into contact with the head as the head oscillates
As I said - I also tested it with my bare hand, nothing mounted to the drum. I felt the slightest contact between vibrating head and skin, so I'm sure absolutely nothing touched the head, although the pitch changed.

I still think it has to do with air pressure between the head and the damper, not with reflections of sound waves. Compared to the surface of the plate the surface of the gap around is very small, hence the air isn't able to compensate the fast changes in pressure generated by the vibrating head by "pumping" air in and out the volume between head and damper.

I did another test, this time using an acoustic guitar. Strings also produce sound waves, able to being reflected. But they are no flat surface like a drum head, not producing measurable air pressure. I grabbed a wooden slat, long enough to cover most of the length of the strings, leaving a gap towards the bridge to activate them, covering a lot more of the string percentage-wise compared to the "tiny" damper above the snare head. No matter which string I pulled in which direction - absolutely no change in pitch. This to me also seems like a hint that it's about the air pressure in the gap.

The surface of the damper currently is covered with felt. Maybe I'm able to somehow measure a difference between different materials, this would point in the same direction since acoustic foam for example should produce much more friction towards air passing by than e.g. glass.

Maybe there's no need to discuss this thing to death, although it triggers the tiny explorer wearing a funny hat inside of me.

giphy.gif


So I'll definitely do some more tests as soon as I find the time to maybe improve what the Gibraltar thingy is doing or to get better control over the effect, since I feel like this is the kind of sound I'm after.
 

Otto

Platinum Member
hmm..try experimenting with holding the damper close to the head then striking the drum...then move it slowly away(holding the mount against the rim to stabilize it then moving the angle of the damper to bring it up millimeter by millimeter)...I am still betting the head and damper are coming into very slight contact as i know its not odd for a drum head to oscillate at least a few millimeters.

great puzzle!
 

Jeremy Bender

Platinum Member
Andy's earlier post regarding tom heads in proximity to a bass drum must be the reason for the moongels on Nick's rack tom reso's along with what appears to be a mufler near the floor toms as well.

thumbnail_nick-mason-favorite-syd-songs (1).jpg
 
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