Acoustic Drum Exploration

-A Basis for Investigation-

Ted Argo IV

University of Oregon

Targo@gladstone.uoregon.edu

Working with Prof. Steve Errede

University of Illinois REU 2002http://www.gmi.edu/~drussell/Demos/MembraneCircle/Circle.html

Overview

• Ideal membrane model

• Sound analysis setup

• Effects of deviations from the ideal model

• Conclusions

Ideal Membrane Model

• Circular Membranes vibrate in certain resonant modes.

• Boundary must be fixed.

• Fractionally related.

http://www.gmi.edu/~drussell/Demos/MembraneCircle/Circle.html

Fundamental (0,1) Mode

Second (1,1) Mode

Modes of Vibration

http://hyperphysics.phy-astr.gsu.edu/hbase/music/cirmem.html

Sound Analysis Setup

Drum

Microphone

LabPC Card

Computer

LabVIEW Setup

FFT Graph

Data Saving Entries

Oscilloscope Trace

Sampling Parameters

Peak Detection

Effect 1: The Drum Shell

• Each shell has specific resonances.

• Shells are made from many different materials.

• Gretsch 13” x 9” Tom• Resonates at 556 hz,

992 hz, 1549 hz, and 1844 hz.

www.repercussions.org/ 8gretch_jpg.jpg

Effect 2: Single Heads• Distance test

• Center, 1, 2, 3, 4, and 5 inches from center as test points.

• Evans Genera G1:• 1 ply drum head.

• Closest to ideal membrane model.

• Evans Genera G2:• 2 plies with a trapped

oil layer.

• Large deviation from ideal membrane. www.drum-set.biz/

Effect 3: Sticks

• Different tip shapes and materials may cause different harmonics to appear.

• Vic Firth Test Sticks:• 5B – Average weight

and shape for a band.• 5BN – A 5B with a

Nylon Tip.• Gregg Bissonette –

Thicker and heavier than a 5B.

http://www.vicfirth.com/product/manu-facturing/manufacturingmain9.html#

Effect 4: Tuning

• Tuning pattern is important to ideal model.

• Different Tensions cause different harmonics.

• Each variable tested at 4-5 different tensions.Drum Head Tuning Pattern

Effect 5: Resonant Head

• By adding a second head,many new resonances appear.

• Both heads have individual resonances.

• There are beats between the two heads creating more internal frequencies.

Tuning Summary:1.78 1.81 2.69 3.14 3.86 5.13 Mode Multiple

148.14 262.79 268.26 398.31 464.63 570.58 758.85 Average Frequencies Down a quarter turn0.03 0.01 0.02 0.01 0.01 0.01 0.01 Average Amplitudes0.00 0.00 0.00 0.00 0.00 0.00 0.00 Average Error1.81 2.10 1.51 12.65 11.76 0.00 2.57 Percent Error1.00 0.33 0.72 0.20 0.25 0.15 0.24 Normalized Amplitude0.02 0.01 0.01 0.03 0.03 0.00 0.01 Normalized Error

Genera G2 Batter, G1 resonant, Vic Firth 5BN Sticks, Gretsch 13"X9" Tom

Effect 6: Distance

• The distance from the center at which the head is struck determines its sound.

•Distance tests at 6 distances:•Every inch from center.

•Each other test at 3 distances:•Center, 2 inches, and 4 inches.

Other Considerations

• Hardware on the shell• Interrupts sound path.

• Damps shell resonances.

• Bearing edge• Variously pointed or

rounded edges.

• Changes coupling of head to shell.

• May change boundary conditions of ideal membrane.

Bearing edges and hardware

www.acousticdrums.com/ members/refinish.html

Conclusions

• The ideal membrane model does not hold for a complex drum system.

• There are many different deviations from the ideal model.

• Some real-world playing preferences are observable.

• More tests can be performed on different equipment.

• This is the low-cost easy-accessibility solution.

Acknowledgments• Prof. Steve Errede – Project Advisor.

• Nicole Drummer – Equipment and ideas.

• Adam Kempton and Eric Moon – Sharing Lab Space.

• University of Illinois – Hosting the REU program.

• The National Science Foundation:This material is based upon work supported in part by the National Science Foundation under Grant No. 9987906. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation.