Sound is the physical thing we are most familiar with, and almost all of us know it. However, before we get into that, I have a question: do you really know about sound? I don't think I understand. So, let's talk about sound. Sound is a mechanical wave produced by the vibration of an object, not a wave of matter. Some people will say that sound is not composed of phonons, and how can it become mechanical waves? It turns out that phonons, like photons, have wave-particle duality. It is said that in the Spring and Autumn Period, there was a princess of the Song Kingdom called Shengzi. Can heat make sound? OK. This is evidenced by the thermally induced acoustic effect. Does sound have energy? Of course. The acoustic cooling effect is a good example of this. Hey, I remembered the sonic power. Maybe to a certain extent, sonic waves really can. Is sound wave and sound wave equivalent? There is no difference, it's just a different name. Mizukawa is talking about some of them.

Sound pressure is not a new type of pressure, but only a type of atmospheric pressure. It turns out that sound waves, when transmitted, change the atmospheric pressure in the surrounding air, resulting in a significantly different pressure distribution. Acoustic impedance should be a quantity that describes the resistance experienced by sound as it propagates, somewhat similar to the impedance in an electric current. The sound neck is an acoustic physical quantity! What is sound quality? Sound is made up of phonons, which have no rest mass. In other words, sound has no static quality. So, is this referring to the quality of movement? Actually, no. In language, mass usually refers to the quality of an object rather than the mass in physics. In electroacoustics, it refers to the fidelity of electrical signal transmission. Margarita said a few words.

Photoacoustic and acousto-optic effects are two effects that are extremely confusing. Let's take a look at what they mean! The photoacoustic effect refers to the fact that when an object is periodically illuminated, the object absorbs photons. This results in a change in temperature, causing volume fluctuations. The fluctuation of volume can be seen as a manifestation of the vibration of an object, and the vibration of an object produces sound. So, that's how the sound was created. The acousto-optic effect refers to the diffraction that occurs when light passes through an object medium that vibrates and emits sound.

Do you know about phonon crystals, molecular crystals, phonon traction effects? I don't know? Actually, I don't know either.

We know that both phonons and photons have zero rest masses, so why is the speed of light so much faster than the speed of sound? Recall that in the past we mentioned the mass at rest when we explained why the speed of light is the speed limit. If we follow the previous thinking, the speed of the phonon must be the speed of light. However, this is not the case. For the huge difference between the speed of light and the speed of sound, it has been explained that photons can travel in a vacuum, and phonons need a medium. What does this mean? Things are far from being as simple as they seem. I was thinking, why does it need a medium when the phonon has zero rest mass? Or why are photons more special than phonons? The reason is actually quite simple. Photons are static information particles, while phonons are dynamic information particles. In network information, a video uses a lot more traffic than a photo. Liuzi Feng came to say a lot in one breath.

Let me talk about the connection between light and sound. Did you know? Phonons are divided into optical and acoustic, and acoustic ones are divided into longitudinal phonon and transverse phonon. The criterion for division is phonon frequency. The high frequency is the optical phonon, and the low frequency is the acoustic phonon. Of the two types of optical phonons, the one with the highest phonon frequency is the longitudinal phonon. Did you know? Phonon scattering is elastic scattering.

Well, that's all said and done. Everyone goes their own way. Dueñas concluded.