Can a gun break glass with just sounds alone?

Well, my military experience says glass can feel safe from regular gun sounds.

We were using H&K AG3 with 7.62mm ammo, which is pretty strong as guns go. Both outdoor and indoor ranges. Bottles, windows, my glasses, windshields, mirrors, never had anything crack.

So it would have to be a very constructed setup and very brittle glass for it to break glass.

It's possible but not likely or common. Glass is stronger than most people give it credit for. Most "hollywood" glass is actually panes of sugar. You could certainly arrange things so that the gun's pressure wave has a good chance of stressing and breaking glass, but it would take special preparations and effort and the gun would probably have to be very close to the glass. It's almost unheard of for it to happen normally unless you specifically shoot at the glass.

Someone like mythbusters could probably test this pretty effectively, but based on my experience around guns and glass, I suspect they'd come to the same conclusion.

A not directly related but still interesting video was done by the slowmo guys on youtube

In theory? Yes.

In practice? Probably be easier to bash it in?

It’s not the frequency that matters, it’s the pressure wave. When any gunpowder-based weapon fires, the expanding gassed from the sudden conflagration of gunpowder doing its thing, right?

Those gases keep expanding even after leaving the muzzle. You can see that in this picture of the USS Iowa firing- the muzzle blast expands spherically and the displacement on the water creates a shallow depression.

If that blast was strong enough and sharp enough, it could break glass, yes. It’s dubious that any standard firearm could just from the muzzle blast alone. But you make a big enough gun with fast enough powder… sure.

Technically, yes.

Soundwaves are made up of pressure waves. A pressure wave results from the explosion of the propellant of a firearm's ammunition. The explosion works just like any other explosion, creating an overpressure blast, which is the fast onset of a pressure wave. If the glass is hit by such a pressure wave, it can break.

However, the explosion created by ammunition tends to be fairly small, and in a bare barrel is widely dispersed. The pressure quickly dissipates.

What would cause a break to happen would be if a gun were fitted with a muzzle brake, picture here(It's the square dealie on the very end of the barrel). The vents on the side of the brake funnel the pressure wave tightly in a specific direction. If glass were in the path, yes it could break. Higher caliber means, generally, bigger explosion, which means more pressure.

Here is a video example of it happening to a tail light. I understand it it plastic not glass, but I think you get the idea. Youtube link, I apologize. Video. The muzzle brake is right up against tail light in way way that funnels the pressure wave directly at it. This is possible through a combination of a very large caliber firearm and very close contact to the object. Reduce the caliber and/or moderately increase the distance, and the outcome will change.

This is not the stereotypical "high pitched resonance makes glass shatter" situation, this is the energy being funneled to make a pressure wave shaped hammer situation.

Sound waves are energy traveling through the air. Energy is what causes stress, strain and failure in materials. Yes, a loud gun, especially at the right frequency, could break things with a relatively low failure point.

Explosions frequently break glass and a gunshot is basically a small, controlled explosion.

The answer probably needs to have a whole lot of "it depends"

What kind of firearm, what kind of glass, thickness of the glass, how far away was the gun when it was fired, etc. will probably all have an effect, and maybe even some more exotic variables, resonant frequencies, atmospheric conditions, temperature,angle you fired the gun at relative to the glass, etc.

Glass absolutely can be broken by vibrations and pressure waves similar to those made by a gunshot, and I would probably expect a high caliber supersonic round fired within inches of a thin piece of weak, brittle glass to break the glass, and on the opposite end of the spectrum, a low powered subsonic round fired far away from a thick piece of strong tempered glass I would expect to have little to no effect whatsoever.

Those are both fairly extreme examples, and I certainly don't have the science/mathematic background to tell you where the limits are in the middle.

I wonder if the discharge of a regular firearm would shatter movie glass — it’s essentially sheets of sugar, designed to crumble easily without sharp edges. Doesn’t take much force to break it and it’s not as flexible as real glass.

Certainly if you use a big enough gun.

With a pistol or normal gun, probably nothing will happen.

With an anti material rifle you might get some luck if you are close enough.

Or you just take a tank cannon or artillery, those should have plenty of muzzle blast.

Define "gun".

If you're okay with scaling up, then the answer is yes. M777s can easily break glass for any windows nearby.

This is a good question and it certainly has me stumped.

ChatGPT says it's possible and that it's "not uncommon" for this to happen. It calls the phenomenon "acoustic or sonic glass breakage."

Yet, Myth Busters disproved it in one of their episodes.

https://mythresults.com/curving-bullets

If I had to wager on it, I'd place my money on the Myth Busters having the correct answer and not ChatGPT, however.

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Yeah. But the frequency of the sound has to match the resonance of the glass. Any sound can break any glass if they resonate strongly enough to make the glass vibrate violently enough to break. This is pretty hard to do, even when you can control the acoustics of the sound being using to shatter the glass (IE when a singer breaks a wine glass). Finding the right gun and right glass to make it work would be like finding a needle in a haystack.

Using a large enough gun that creates a sonic boom I'm not sure counts. It's not the sound itself that is breaking the glass at that point, but the concussive force of the wave traveling at high speed.