Can Singing Really Break Glass?

Can Singing Really Break Glass?
Photo by Jason Rosewell / Unsplash

Have you ever wondered if the movies were true when the opera singer belts out that really high note and the glass around them shatters? I certainly have! Just for fun, I decided to do a little bit of research into whether or not this is true and some of the cool science-y stuff behind it.

It is possible to break glass with the human voice by matching the frequency (pitch) of your voice to the resonant frequency of the glass, and reaching a volume louder than 105dB (decibels). Each glass will have a different resonant frequency, but most will lie within the human vocal range, between 300-3400Hz.

This science has been proven time and time again as science and technology advances. This leads to questions about whether we can shatter other objects with sound alone. Read on to find out more!

How Glass is Shattered by Your Voice

Diving deeper into the science, this particular phenomenon uses physical principles. Particularly sound-wave physics. As a sonographer, I always find this stuff very interesting, but I will keep it more simplified for the sake of both our brains.

Match the Resonant Frequency with Your Voice

Every object has what is called a resonant frequency. This is basically the sound it will emit when it vibrates (or is tapped). Frequency is measured in Hz (Hertz), and is the number of vibrations per second within the object. The frequency of sound is what gives us our pitch when we sing. Every pitch, or note, has a corresponding frequency. Lower frequencies for low notes and higher frequencies for high notes.

So when you listen to the sound a glass makes when you tap it, that pitch is equal to its resonant frequency. This is the pitch you will need to sing to make the glass break. More specifically, you will need to be 0.5Hz either above or below that exact frequency (the tiniest off-set in pitch) to be able to cause the distortion. This isn’t necessarily a bad thing, because when we sing and think we are hitting a note, our voice is actually fluctuating ever so slightly around that frequency, never perfect.

This may be why it took Jaime Vendera, one of the very few singers who have actually succeeded, a good 13 attempts before nailing the right frequency and volume to break a glass.

But what is the frequency required to break a wine glass? It varies from glass to glass, so you will need to find the answer to this before you can match your voice to the same frequency.

I had a little bit of a play at home, and my wine glass sounded close to F#5, which is about 740Hz. Now there’s a bit of basic musicianship required to know exactly what I mean, but for context, most women can sing between 175Hz-587Hz. So this particular frequency is little bit too high for your average female singer.

A typical soprano singer (higher vocal range) however can sing up to 880Hz. With this, things are starting to look promising. With hard work and regular practice, singers can also train themselves to sing higher.

Sing as Loud as Your Can... and Then Some

Next we have the volume. The volume of your voice is what causes the glass to shatter once you have matched your pitch to the resonant frequency of the glass. If volume wasn’t a factor, glasses would be shattering left, right and center if that resonant frequency is within range of the female (and sometimes male) voice.

The volume required depends on the material, but for glass, this is anything greater than 105dB (decibels). Just talking normally, we hit around 50dB in volume. The threshold for the human ear is around 120dB before it becomes damaged, so getting close to that volume is actually very difficult. However, with enough skill and training, some singers are able to reach these levels.

If you can achieve these two things, and hold that loud note for up to 20 seconds, you will be able to shatter a glass with your voice. It’s actually very cool to see – if the increase in volume is just right, the glass will first distort in ways that you never knew possible, before finally shattering. Saying that, I wouldn’t recommend trying it. A much easier way of seeing this is to just jump on YouTube.

Breaking Other Objects with Singing

This then got me thinking. Can you break other objects with your voice? Technically, with the right volume and the right frequency, you could.

The problem is, glass is very easy to break compared to other objects (as we have all discovered at some stage in our lives). So the volume we would need to break another object would be immense, way too loud for our voices to achieve. It may even be too loud to achieve with technology today. If it’s harder to break by throwing it on the ground, chances are it’s going to be a lot harder to break with your voice!

The next issue here is the resonant frequency. A glass is a convenient frequency that is within range of the human voice. Most other objects, however, are a whole lot lower than that when we tap them. They have very low resonant frequencies. Some of these frequencies are just not possible with the human voice. With a killer bass and mammoth subwoofer, maybe. But again, we would need a whole lot of volume to go with that.

Can Loud Music Break My Car Windows?

One thing that people have tried is the old ‘break the car windows with music’ trick. This is actually possible! Probably because we are again working with glass, but it’s still pretty impressive.

Now when I say possible, I don’t mean with the human voice. Sorry! Glass used in a car window is a lot stronger than a wine glass and a different shape, giving it a much lower resonant frequency. Do you hear a lovely ringing sound when you knock on someone’s window? No. It’s more of a dull thud. A low sound.

So there are two ways that this is possible. One would be to play very very loud music in a completely air-tight car. Because sound waves manipulate the air around them, the loud music in a car will be pushing air around your car. You can feel this when you put your hand in front of a subwoofer. It feels like a little puff of air comes out.

Well the louder you crank that music, the more force you will feel in the air around you. So if the car is air-tight, the air pressure within the car starts changing. The pressure within the car will then get to a point where the weakest part of the car will give in, and if that’s the windows then you’ve done it. You’ve shattered the windows with your ridiculously loud music.

The only problem is, cars are never truly air-tight. Does a car float along a river with all the doors closed? No. It will sink because there are still tiny cracks that air or water can get through. So playing your loudest song as loud as you possibly can is never going to create enough pressure in the car to blow the windows, because the air will just leak out the cracks to relieve that pressure.

The second possible way is to go back to our physics. We need to hit that resonant frequency of the car window glass for a prolonged amount of time (which is not likely to happen in your average radio hit). If you can get that perfect note for a long enough amount of time, you will not have to rely on cabin pressure to blow out the windows. The distortion from the resonant vibrations will do it for you. It will still take a lot of volume, but you don’t need that air-tight environment.

So find that deep, deep bass note that matches the right frequency for the glass on your car, crank it loud enough and you have yourself a successful (and very costly) scientific experiment. This one has been tried and tested. Your windshield will crack and you’ll probably be hearing ringing in your ears for days.

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