Duality of sound - is sound a particle or a wave?

Sound, like light, has a dual character.

Sound moves like particles in some properties, but waves in others.
Sound is a mixture of the properties of particles and waves.

Starting from a particular section, some sections move completely like particles, and others move completely like waves.

What separates a particular section is the area of frequency (high, middle, and low tones)

In a section that has both particle and wave properties, the higher the frequency, the more the particle property is gradually shown, and the lower the frequency, the more the wave property is.

High frequencies move like particles

Low frequencies move like waves

The mid-low range moves like a wave, but as the frequency increases, it becomes more particulate.

What does it mean that high frequencies have particulate properties?

If you think about the volume of the sound first, when we hear it in front of the speaker, our ears hurt because of the loud sound. However, if you move farther and farther back, you can naturally feel the sound being heard quietly.

And the sound has an incident angle and a reflection angle, so the sound bounces from the wall to the wall like a table tennis ball.

This can certainly be seen as a particle's property.

There is a technology that tracks sound with light, which tracks sound from a speaker through laser beams.

This technique is to track the movement trajectory of sound through the properties of high frequency.

It is a method that takes into account the characteristics of high-frequency moving like light.

The high-frequency area also has particle properties to some extent, but as it goes up to a higher frequency, the directivity (Q-value) becomes narrower and narrower and narrower.

The monitor speakers that we often see are made up of a woofer and tweeter

The tweeter is actually designed at a fixed angle.

It is designed by adjusting the angle at which high frequency spread in consideration of the directionality of high frequency.

The speaker is basically configured with a stereo system (Left, Right), i.e. two channels

If the listener's listening point is exactly centered on the stereo image,

You can hear all the left and right sounds,

If you move to either side and listen, only the speaker nearby will hear relatively louder. This is a very natural phenomenon for us.

This phenomenon means that sound has direction.

If sound has no direction, the sound should all sound the same size wherever you can hear it, such as on the left, right, or center.

This phenomenon is felt because of the directionality of the high frequency.

Of course, the low-pitched sounds aren't exactly the same depending on the location, but especially for people sitting back and forth, and they can feel a bigger difference depending on who is listening closely to the wall.

With this phenomenon, we can see that high notes are oriented and low notes are not oriented.

Low-pitched sounds are more of a wave property.

You can feel that the sound is louder when you go to the wall and listen to it than when you are close to the speaker.

If you think of a ping pong ball as a particle, for example, the farther the distance it flies, the less powerful it becomes (the sound gradually decreases)

For low-pitched sound (wave), it feels louder to hear it closer to the wall opposite the speaker than to hear it in front of the speaker.

What a strange phenomenon.

The volume of the low sound is felt the largest on the wall located on the other side of the speaker, and the closer you get to the left and right walls, the louder the low sound is felt.

The most serious place is Corner.

Since the corner is a section where low-pitched sounds amplified on each wall are clustered, it is the place where the most bass problems occur in the space.

Therefore, to solve the resonance problem of the corner, we install the Bass Trap.

You need to listen to the sound from the speaker for accurate monitoring, but the amplified sound becomes louder as it hits the wall than the sound from the speaker (Bass Booming problem)

In order to establish a more accurate monitoring environment, Bass Trap should be installed.

This is one of the room acoustic problems caused by the nature of low-pitched waves.

Another characteristic of waves is that they are not oriented, unlike particles.

It does not have directivity like high frequency but spreads in the overall direction (360 degrees). This is called the Omni Directive.

In particular, there is little directivity below 125 Hz.

High-frequencies particle properties and low-frequencies wave properties.

These do not suddenly change from wave to particle at any point in the frequency.

The area that separates the wave property from the particle property depends on the size of the corresponding space.

As the space becomes larger, the frequency point interval in which the properties of waves are expressed gradually decreases.

Therefore, it is important to calculate the Schroeder Frequency well and proceed with room acoustic treatment tailored to the space.

-Ted Kim