Sound, Mass and Magnetic Fields

Sound, as we commonly understand it, is just a vibration that travels through air, water, or solid materials. It’s what we hear when air molecules move back and forth, creating pressure waves. But in recent years, scientists have discovered that sound is more than just a simple vibration, it can carry mass and even influence or interact with magnetic fields under certain circumstances.

Sound Carrying Mass

Traditionally, we thought of sound as having no mass. It’s just energy moving through a medium. However, recent studies have shown that sound waves can actually carry a tiny amount of mass as they move through a material. Think of it this way: when a sound wave moves through water or air, it doesn’t just vibrate the molecules; it also slightly shifts them in a way that creates a small amount of mass. This mass is gravitational mass, which is what we think of when we think of an object’s weight. So, in a way, sound is like a tiny, invisible “object” that has a weight of its own, even though it’s not something we can easily see or feel.

This surprising result means that a sound can very slightly “bend” space-time or be deflected by gravity, much like any object with mass.

But how much mass are we talking about? Well, for example, if you had a sound wave of about the same power as a person speaking at normal volume for 1 second, it could carry a tiny fraction of a milligram of mass. While this is incredibly small, it’s still a real, measurable effect. This discovery suggests that sound has a subtle connection with gravity; in the right conditions, sound could even be slightly affected by gravity or influence the space around it in a tiny way.

Sound and Magnetic Fields

Normally, sound doesn’t have any magnetic properties because it’s not made up of charged particles. However, scientists have recently shown that sound waves in certain materials can actually interact with magnetic fields. In fact, sound waves can be affected by magnets in some materials, and under the right conditions, they can even create small magnetic effects.

One fascinating experiment showed that in some materials, sound waves can “carry” a magnetic property as they move. For example, when a material is exposed to a strong magnetic field, the sound waves passing through it can interact with that field, slightly altering their movement. This is similar to how electric currents can create magnetic fields, but in this case, it’s the sound waves (not electric currents) that are involved. The key here is that the vibrations of sound in certain materials can influence or be influenced by magnetism. This could open the door to new technologies that use sound in ways we haven’t thought of before.

Why Does This Matter?

While these discoveries are still in the experimental stage, they challenge our understanding of sound. Instead of thinking of sound just as vibrations in the air, scientists are starting to realize that sound has subtle but important connections to other fundamental forces, like gravity and magnetism. This is not only opening up interesting possibilities for new technologies and applications in areas like materials science and quantum physics, but also providing further hints on how the “magic” of sound works in modalities such as sound therapy and vibrational healing.

References

1. Nicolis, A., Penco, R. (2018) Gravitational Mass of Sound Waves in Fluids and Solids.
2. Esposito, A., Krichevsky, R., & Nicolis, A. (2019) Phonons, Gravity, and Effective Field Theory: A New Perspective on Sound’s Mass.
3. Jin, H., et al. (2015) Magneto-phononic Effects: How Sound Waves Respond to Magnetic Fields in Semiconductors. Nature Materials
4. Nomura, T., et al. (2019) Magnetochiral Phonons: Controlling Sound Waves with Magnetism in Chiral Crystals. Physical Review Letters
5. Baydin, A., et al. (2022) Zeeman Splitting of Phonons and Phonon-Magnetic Interactions in Semiconductors. Physical Review Letters
6. Tang, C., et al. (2024) Chiral Phonon-Induced Magnetization: A New Way to Control Spins Using Sound Waves. Science

Check our other articles