Metamaterials in musical acoustics: A modified frame drum

Area of Science:

• Acoustics
• Materials Science
• Musical Instrument Design

Background:

• Mechanical musical instruments have limited timbre variability compared to electronic ones.
• Recent advancements focus on extended playing techniques and sophisticated instrument design to overcome this limitation.
• Metamaterials offer potential for significantly extending the sonic capabilities of mechanical instruments.

Purpose of the Study:

• To investigate the use of metamaterials to enhance the timbre variability of mechanical musical instruments.
• To explore the acoustic effects of attaching mass rings to a frame drum membrane.
• To assess the potential for creating novel musical sounds and articulations.

Main Methods:

• A frame drum (40 cm diameter) was modified by attaching rings of 10 masses each at 8, 10, and 12 cm diameters.
• Vibrational cloaking behavior was measured using microphone arrays and high-speed laser interferometry.
• Acoustic band gaps were analyzed based on the resulting sound characteristics.

Main Results:

• The attached mass rings induced vibrational cloaking, preventing vibrations from crossing the ring.
• Acoustic band gaps were observed between approximately 300-400 Hz and 700-800 Hz, varying with ring diameter.
• The 8 cm diameter ring demonstrated the strongest amplitude attenuation within the band gap.
• Striking the drum outside the ring produced a conventional drum sound, while striking within the ring generated a unique band gap sound.

Conclusions:

• Metamaterial principles applied to a frame drum can create distinct acoustic band gaps.
• This technique significantly enhances musical articulation possibilities, allowing for sounds unattainable with traditional drums.
• The study demonstrates a novel approach to expanding the sonic palette of mechanical musical instruments.