Dampening by air cushion only

Supergrobi

Technical Supervisor
Staff member
Lately I stumbled over a strange but very useful effect: dampening a drum using just air.

I bought a Gibraltar SC-4235 External Mute recently. And it sucks. Not only doesn't it get a good grip on my die cast hoops, but also the screw of the clamp can only be moved with difficulty. Sound-wise if I attach it to my snare drums batter, the drum starts to sound boxy and dull immediately. Yeah, it definitely sucks.

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Yesterday I once again thought "can it be that bad?" and put it on the snare again. And yeah, it still sucked. Since the screw is so stiff I just used the one on top to raise the felt until it didn't touch the head anymore to go on with playing. So I turned the screw to its end, lifting the pad about 2mm (~1/10") above the head. By the way - the dampener is a bit less than 2x5".

Hitting the snare afterwards didn't sound like what I expected - my open snare drum sound, but a bit dampened, not in a bad way, just not that ringy towards the rim(-shot), no resonance when hit dead center and a bit less excited snare buzz. So I checked if maybe some corner of the pad still touched the head or so, but no. After removing the dampener completely the open sound was back. So I started testing with my bare hand - same effect. I mentioned that the frequency of the drum also got a bit lower on approaching, maybe 1/8th note (it is tuned in the higher range, but not cranked at all).

I'll test this with the Gibraltar device for recordings soon, sounds like the perfect compromise, since I generally like the dryness of the drums dead center while still being able to set ringy accents by moving towards the rim. Every other dampening removing the last bit of resonance from the dead spot also killed the ring, this approach basically leaves it where it is.
 

MrInsanePolack

Platinum Member
I have a thought. What if the Gibraltar damper is blocking/absorbing/reflecting sound waves and that is altering what you hear? Like an empty room vs a furnished room. The furnished room is much more dead (that sounds funny). If you use a larger object, is the effect greater? And does the effect decrease as the object gets farther away from the head (1mm vs 1cm for example)?

Perhaps it's working in conjunction with the air cushion?
 

Andy

Administrator
Staff member
The affect of proximity of a surface to a drum is well observed. Think in terms of a tom resonant head close to a bass drum shell, or floor tom resonant head close to the floor. I don't fully understand the mechanisms at play, but broadly speaking, sound / pressure waves are disturbed in a way that affects the instrument response. The affect is often one of dampening note sustain or overtones, but also of perceived pitch change. By adding a mass close to one area of the snare head, you're effectively detuning one part of the head, and as we all know, if we do that through physical means, it often results in dampening higher overtones.

I find the biggest impact of this affect is with floor tom reso heads proximity to the floor / stage. The closer the head, the more lower frequencies are removed from the resolved sound, and the shorter the head sustain. This is the main reason I prefer 14" deep 16" & 18" floor toms.
 

Lefty Phillips

Well-known Member
Drums are acoustic instruments. I'm much more familiar with guitars, but damned near EVERYTHING, every single detail, is capable of producing an audible result on the voice of the instrument.
 

Andy

Administrator
Staff member
Andy from your observations, how far from the floor does the bottom head need to be?
I don't have a measure, but in my experience, the bigger diameter the drum, the bigger affect at a given distance. Of course, whether you notice an affect or not, depends on how resonant your floor tom is in the first place. My drums are very low mass, so I pick this up maybe more than most.

In practical terms, I can only use my playing example. I'm 6ft tall, so you can judge my approximate floor tom height from that. At that height, if I lower my 16" x 14" floor tom by a further 2", I can hear the difference.

Here's an easy test. Take your floor tom (without legs attached), hold it in one hand by the hoop at hip hight, keep it as level as is practical. Strike the head, then immediately lower it a lot closer to the floor, & hear how the response changes. If you have someone to assist, hit the drum whilst your assistant holds the drum (lightly from under the top hoop) at different heights.
 

Supergrobi

Technical Supervisor
Staff member
The affect of proximity of a surface to a drum is well observed. Think in terms of a tom resonant head close to a bass drum shell, or floor tom resonant head close to the floor. I don't fully understand the mechanisms at play, but broadly speaking, sound / pressure waves are disturbed in a way that affects the instrument response. The affect is often one of dampening note sustain or overtones, but also of perceived pitch change. By adding a mass close to one area of the snare head, you're effectively detuning one part of the head, and as we all know, if we do that through physical means, it often results in dampening higher overtones.
I've never heard a tom close to the bass drum changing its pitch. Same for a low floor tom. But you made me curious so I'll give it another try later, explicitly checking the pitch while whirling my drums around. Putting a tom on the carpet for tuning for example does in fact alter the pitch big time - but in that case it is going up, hand or dampener above the batter head lower the pitch in my case.

By adding a mass close to one area of the snare head, you're effectively detuning one part of the head
I'd like to know more about how approximating mass towards the head effectively detunes it. Could you please explain or point out some links to papers?

Like an empty room vs a furnished room.
This is part of altering the resonance but I don't see how it would change the pitch.

If you use a larger object, is the effect greater? And does the effect decrease as the object gets farther away from the head (1mm vs 1cm for example)?
For the second question, yes. I'll test both later, I'll also experiment with what happens on the reso side.

If I find the time today.
 

Supergrobi

Technical Supervisor
Staff member
Here's an easy test. Take your floor tom (without legs attached), hold it in one hand by the hoop at hip hight, keep it as level as is practical. Strike the head, then immediately lower it a lot closer to the floor, & hear how the response changes.
Adding movement is a different effect called Doppler. Since you're moving away from your ears the pitch would get lower while in motion, same as sirens.
 

cbphoto

Diamond Member
I’ve been experimenting with various muting methods and got the same results.
 

Supergrobi

Technical Supervisor
Staff member
I’ve been experimenting with various muting methods and got the same results.
Do you effectively use this method with nothing actually touching the head in recordings or live?
 

cbphoto

Diamond Member
Do you effectively use this method with nothing actually touching the head in recordings or live?
I have not. I needed a more dead sound with a very fast decay. In addition, the Air Gap Mute did not stop any sympathetic resonance (which, when eliminated, really dried out the sound of the kit in the OH mics and improved the drums in the mix).
 

wildbill

Platinum Member
I forget the details, but think in terms of how the wavelengths of various sound wave frequencies affects their absorption.
 

GetAgrippa

Diamond Member
Probably with just a 2 mm rise the vibrating head sporadically does touch the head or reflected waves stifle the head at that point changing the whole dynamic of head vibration. I wonder if just adding mass to the rim is changing it? Like adding hardware does.
 

GruntersDad

Honorary Lifetime CEO
Staff member
I'm guessing it took some ring out of the hoop. It would dampen the hoops vibration. The sound would be affected.
 

larryace

"Uncle Larry" - Administrator
Staff member
Word police here, you're all under arrest for..well if you don't know, I'll have to let you go with a stern warning and a slap on the keyboards.

OMG it's damping not dampening! You guys are killing me!

John, since you seem to be the only one who understands this, would you be interested in being a deputy for the word police in addition to your responsibilities as a mod? I'll give you a gun...

You don't get a wet sound by dampening, just sayin'
 

someguy01

Platinum Member
Word police here, you're all under arrest for..well if you don't know, I'll have to let you go with a stern warning.

OMG it's damping not dampening! You guys are killing me!
Maybe the felt is wet Larry, so it's dampening damping? LOL
 

GetAgrippa

Diamond Member
I have dysgraphia I saw "dam-pening". He stuck that dam-pening damping thing to his drum rim and didn't work cause it ain't got any GAS in it LOL.
 

GruntersDad

Honorary Lifetime CEO
Staff member
Number 2.


gerund or present participle: dampening
  1. 1.
    make slightly wet.
    "the fine rain dampened her face"

    Similar:
    moisten


    damp


    wet


    dew


    water


    irrigate


    humidify


    bedew


    sparge


    humify


    humect


    Opposite:
    dry


    drench


  2. 2.
    make less strong or intense.
    "nothing could dampen her enthusiasm"

    Similar:
    lessen


    decrease


    diminish


    reduce


    lower


    moderate


    damp


    damp down

    put a damper on


    throw cold water on


    calm


    cool


    chill


    dull

    Professor Larry needs to widen his horizon. It has been dampened.
 
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