# Acoustic Levitation (DD-394)

> In acoustic levitation, ultrasonic transducers send sound toward a reflector or an opposing transducer, creating a standing wave with alternating high- and low-pressure regions. Small objects such as water droplets settle at the pressure nodes, where acoustic radiation pressure balances gravity. The footage shows droplets floating in a levitator.

- Department: Science
- First published: 2024-11-27
- Last updated: 2024-11-27
- Permalink: https://detailenjoyer.com/case/acoustic-levitation/
- Author: Marcus Easterling (DetailEnjoyer), The Detail Department

## Quick facts

- **DD-394-F01**: Ultrasound is used. _(Write-up · Exhibit A (Sound))_
- **DD-394-F02**: Reflected sound makes a standing wave. _(Write-up · Exhibit B (Standing wave))_

## Write-up

Sound waves can hold water droplets in midair. The droplets sit at the quiet points of a standing wave.

1. **Sound**: Ultrasound is used.
2. **Standing wave**: Reflected sound makes a standing wave.
3. **Nodes**: Droplets sit at nodes.
4. **Balance**: Radiation pressure balances gravity.
5. **Small**: Works for small objects.

## Related case files

- [Computer Wave Control (DD-356)](https://detailenjoyer.com/case/computer-wave-control/): I linked more wave physics

## Reel vs. record

- **Note**: None needed.

## Video: Acoustic Levitation: Sound Waves Can Hold Water Droplets in Midair

- Duration: 22.5 s · Published: 2024-11-27
- File: https://detailenjoyer.com/assets/videos/DC4cppsJZ0S.mp4

### Transcript

Did you know, levitating water droplets with sound is achieved using a phenomenon called acoustic levitation, where high-frequency sound waves create standing waves. In this process, ultrasonic transducers generate sound waves that travel upward and reflect back from a surface, creating regions of high and low pressure, known as nodes and antinodes. Water droplets can be suspended at these nodes, where the pressure from the sound waves counteracts gravity. NOW YOU KNOW!

## Questions & answers

**Q: What lifts the droplets?**  
A: Ultrasound. _(Source: Write-up · Exhibit A (Sound) · Wikipedia: Acoustic levitation)_

**Q: Where do droplets sit?**  
A: Quiet points. _(Source: Write-up · Exhibit B (Standing wave) · Wikipedia: Acoustic levitation)_

**Q: What wave forms?**  
A: Reflection. _(Source: Write-up · Exhibit C (Nodes) · Wikipedia: Acoustic levitation)_

**Q: What generates the sound?**  
A: High frequency. _(Source: Write-up · Exhibit D (Balance) · Wikipedia: Acoustic levitation)_

**Q: What does pressure balance?**  
A: Holds up. _(Source: Write-up · Exhibit E (Small) · Wikipedia: Acoustic levitation)_

## Sources

- [Wikipedia: Acoustic levitation](https://en.wikipedia.org/wiki/Acoustic_levitation)
- [Wikipedia: Standing wave](https://en.wikipedia.org/wiki/Standing_wave)

## Cite this case file

Easterling, Marcus. "Acoustic Levitation." The Detail Department (DetailEnjoyer), case file DD-394, last updated Nov 27, 2024. https://detailenjoyer.com/case/acoustic-levitation/