The relationship formula between the intensity of a wave and its frequency: I=w?u1/2uρA?ω?.

Suppose the wave speed is u, the energy passing through the section ΔS perpendicular to the wave speed in Δt time: w—energy density,

Energy flow P=wSu=uSρA?ω?sinω(t-x /ω),

The average energy flow p?=w?Su=1/2uSρA?ω?,

So the intensity of the wave is I=w?u1/2uρA?ω? ?.

The definition of wave intensity is the energy passing through a unit area perpendicular to the propagation direction per unit time, which is called the energy flow density of the wave. It is often used to describe the intensity of the wave, that is, the energy flow density is proportional to the square of the amplitude.

The energy flow P is the energy that passes vertically through a certain section per unit time, which is called the energy flow of the wave passing through the section, or energy flux.

Extended information:

Average energy flow

The energy of a wave comes from the wave source, and the direction of energy flow is the direction of wave propagation. The speed of energy propagation is the wave speed. In order to describe the energy propagation of waves, the concept of energy flow density is often introduced. The energy that passes through a certain unit area in the medium per unit time is called the average energy flow through the area.

The average energy passing through a unit area perpendicular to the direction of wave propagation in unit time is called energy flow density.

The greater the energy flow density, the more energy passes through the unit area perpendicular to the wave propagation direction per unit time, and the stronger the wave. Therefore, the energy flow density is a measure of the strength of the wave, and therefore is called the intensity of the wave. For example, the intensity of sound is determined by the energy flow density of sound waves (sound intensity); the intensity of light is determined by the energy flow density of light waves (called light intensity).

Since the intensity of a wave is related to its amplitude, when a plane simple harmonic wave propagates in a medium, its amplitude will remain unchanged if the medium is uniform and does not absorb the energy of the wave. However, for spherical waves, the situation is different.

A sound wave emitted from a given sound source propagates in a medium, and its sound intensity is proportional to the square of its amplitude. Therefore, the greater the intensity of the sound wave, the greater the amplitude of the sound, and the louder the sound. Therefore, sound intensity is a physical quantity that describes the strength of sound. When the sound frequency is , and the sound intensity is about , it can be heard. This minimum sound intensity that causes human hearing is called the audible threshold. Since the range of sound intensity changes is too large, it is inconvenient to express it directly by sound intensity. Instead, it is expressed by the ratio of sound intensity to the audible threshold.

Because the human ear is more sensitive to weak sound waves but not very sensitive to strong sound waves, experience shows that the loudness perceived by the human ear is not directly proportional to the sound intensity, but approximately proportional to the sound intensity. Strong logarithm. Therefore, for a sound wave with a sound intensity of I, the common logarithm of the ratio is used to characterize the intensity of the sound wave, which is called the sound intensity level.

Baidu Encyclopedia-Wave Energy