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Acoustic Levitation

Short answer: 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.

VideoWrite-up2 sources

In collections:Everyday Physics

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What should you know about Acoustic Levitation?

Quick facts. Each one stands alone and has a stable ID you can cite.

  1. Ultrasound is used.

    DD-394-F01 · Write-up · Exhibit A (Sound)

  2. Reflected sound makes a standing wave.

    DD-394-F02 · Write-up · Exhibit B (Standing wave)

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

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!

Burned-in captions, read frame by frame (see transcript.md) · 22.5s Reel ·

Video coming soonAcoustic Levitation · Instagram Reel
Acoustic Levitation: Sound Waves Can Hold Water Droplets in Midair Instagram Reel · · 22.5s

The write-up

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

  1. Exhibit A

    Sound

    Ultrasound is used.

  2. Exhibit B

    Standing wave

    Reflected sound makes a standing wave.

  3. Exhibit C

    Nodes

    Droplets sit at nodes.

  4. Exhibit D

    Balance

    Radiation pressure balances gravity.

  5. Exhibit E

    Small

    Works for small objects.

Questions people ask about Acoustic Levitation

What lifts the droplets?

Ultrasound.

Source: Write-up · Exhibit A (Sound) · Wikipedia: Acoustic levitation

Where do droplets sit?

Quiet points.

Source: Write-up · Exhibit B (Standing wave) · Wikipedia: Acoustic levitation

What wave forms?

Reflection.

Source: Write-up · Exhibit C (Nodes) · Wikipedia: Acoustic levitation

What generates the sound?

High frequency.

Source: Write-up · Exhibit D (Balance) · Wikipedia: Acoustic levitation

What does pressure balance?

Holds up.

Source: Write-up · Exhibit E (Small) · Wikipedia: Acoustic levitation

Test Your Knowledge

All quizzes →

5 questions, all from this case file. Answers are revealed instantly.

  1. What lifts the droplets?

    1. Sound
    2. Magnets
    3. Air jets
    4. Strings
    Show the answer

    Answer: A. Sound Ultrasound. Source: Write-up · Exhibit A (Sound) · Wikipedia: Acoustic levitation

  2. Where do droplets sit?

    1. At pressure nodes
    2. On the transducer
    3. On the floor
    4. Randomly
    Show the answer

    Answer: A. At pressure nodes Quiet points. Source: Write-up · Exhibit B (Standing wave) · Wikipedia: Acoustic levitation

  3. What wave forms?

    1. A standing wave
    2. A tidal wave
    3. A shock wave
    4. A radio wave
    Show the answer

    Answer: A. A standing wave Reflection. Source: Write-up · Exhibit C (Nodes) · Wikipedia: Acoustic levitation

  4. What generates the sound?

    1. Ultrasonic transducers
    2. Speakers playing music
    3. Drums
    4. Voice
    Show the answer

    Answer: A. Ultrasonic transducers High frequency. Source: Write-up · Exhibit D (Balance) · Wikipedia: Acoustic levitation

  5. What does pressure balance?

    1. Gravity
    2. Light
    3. Heat
    4. Magnetism
    Show the answer

    Answer: A. Gravity Holds up. Source: Write-up · Exhibit E (Small) · Wikipedia: Acoustic levitation

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/

Permalink: https://detailenjoyer.com/case/acoustic-levitation/ · Last updated

Markdown version

Cite a single fact by its ID, for example DD-394-F01 → https://detailenjoyer.com/case/acoustic-levitation/#DD-394-F01

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