There is an opinion that a very strong voice can turn glass objects into fragments. We checked if this is true.

Many people remember the wonderful Soviet film “The Magic Voice of Gelsomino” based on the fairy tale by Gianni Rodari. His hero had such amazing vocal cords that he could destroy walls, not to mention an ordinary window. glass. But if the boy achieved this involuntarily, without effort, then in real life everything is different. There are legends that those with particularly impressive vocal abilities (usually opera singers) are able to use their voices to make a small glass object, such as a glass, burst. One of the most famous such legends is about the great bass Fyodor Chaliapin. “When he sang at full power, the candles went out, the chandeliers shook, the cut glasses cracked” - this is roughly how the power of Chaliapin’s bass is described in numerous sources on the web. Chaliapin's grotto near the village of Novy Svet in Crimea received, according to legend, the name comes from the fact that when the maestro performed here, his powerful voice reflected off the walls and smashed the glass of champagne in the singer’s hand to smithereens. On the other hand, the wife of the famous tenor Enrico Caruso in her book refutes a similar legend about her husband.

In the 70s, advertising for Memorex speakers was popular in the United States. In it, the glasses burst from the voice of the first lady of jazz, Ella Fitzgerald. However, advertising is information that should not be believed unconditionally:

Since we are talking about a physical phenomenon here, I would like to have both its theoretical justification and practical confirmation. Let's start with the first one.

Sound is wave vibrations propagated in space with a certain frequency. The wave, reaching the glass, causes it to vibrate. Here we are dealing with a phenomenon such as resonance, which manifests itself in a sharp increase in the amplitude of vibrations when the sound frequency coincides with the frequency of vibrations characteristic of glass of a given thickness, composition and shape.

The harmony of these two frequencies, multiplied by enough power, can cause glass to shatter. In other words, if we use the example of a wine glass, to do this you need to emit a sound whose frequency coincides with the resonant frequency of the glass’s own vibrations. Intuitively, it should at least be a fairly powerful sound. But how to determine its necessary and sufficient parameters?

This is what the famous Dutch professor Walter Levin writes about this in his book “Through the eyes of a physicist":

“I personally have never seen an opera singer breaking a glass with his voice, so I don’t involve them in my experiments. I take a glass, lightly tap it with a spoon and measure its fundamental frequency with an oscilloscope - obviously it varies from glass to glass, but for the ones I use it always ranges somewhere between 440 and 480 hertz. Then I electronically generate a sound of exactly the same frequency (well, it's impossible to do this exactly, of course, but I try to get it as close as possible). I put the glass to the amplifier and slowly turn up the volume. Why am I doing this? Because the louder the sound, the more energy in the form of a sound wave will hit the glass. And the greater the amplitude of vibrations in the glass, the more the glass will bend inward and bend back - until it breaks (which is what I am counting on when conducting a demonstration).

To show that the glass is vibrating, I point the camera close at it and illuminate it with a strobe beam adjusted to a slightly different frequency than the sound. This is simply incredible! You see the glass begin to vibrate; its two opposite sides first converge and then diverge, and the distance by which they move grows and grows as the volume of the speaker increases. Sometimes I have to adjust the frequency a little and then bam! - and glass shards. Students especially enjoy this part of the experiment; they just can’t wait for the glass to break.”

So we smoothly moved on to the experimental part. In Levin's example, the glass was broken using a technical device, but we are interested in the effect of the human voice. It would be natural to wonder whether the creators of the famous program “MythBusters,” who like to test various persistent stereotypes associated with physical phenomena, were dealing with this issue. Indeed, already in the first season of the famous show, an episode called Breaking Glass was released.

To achieve their goal, the creators of the program invited rock singer and vocal coach Jamie Wendera. It was possible to break the glass with the help of an amplifier quite quickly - even the presenters were able to do it. It is another matter to achieve success with just a natural voice. Vendera tried more than ten different vessels before he came across the only one that shattered from his powerful vocals:

For the first time, proof that an unaided voice can actually break glass has been captured on video. It should be noted that in her winning attempt, Wendera's voice reached 105 dB - almost as loud as a jackhammer. This is much beyond the capabilities of an ordinary person. According to the magazine Scientific American, even opera singers train for years to produce sustained notes at volumes above 100 dB.

In addition, one cannot help but pay attention to the dependence on a specific glass. Vessels that look identical to the naked eye can have radically different fracture toughness, allowing some to withstand much more force than others. In other words, success here strongly depends on the location, depth and shape of microcracks.

Nevertheless, the legend, as we have seen, is absolutely true: you can break glass with a human voice.