# [Soundwaves] Energy and decibel

• hiuting
In summary: The dimensions of the window are given as height 2 m and width 2.75 m. In summary, the sound level in a noisy classroom is 101 dB and the energy transmitted through an open window of height 2 m and width 2.75 m in 40 minutes is 166 J. The decibel rating 1 km from the classroom, assuming equal distribution of sound in all directions, is 46.4 dB. The equations used to find these values are I = P / 4(pi)r2 and \beta = 10log(I/I0). The definition of intensity is not specified in the given conversation. The unknown variable v is not mentioned in the given conversation.
hiuting

## Homework Statement

The sound level in a noisy classroom is 101 dB. How much energy in J is transmitted to the outside through an open window of height 2 m and width 2.75 m, if the class is 40 minutes long?. What is the decibel rating 1 km from the classroom, assuming sound is distributed equally in all directions?

## Homework Equations

I = P / 4(pi)r2
$$\beta$$ = 10log(I/I0)

## The Attempt at a Solution

the answers are [P = 0.069 W; E = 166 J; 46.4 dB]

I tried finding v, but I don't know what the dimensions of the window are for.

Hi hiuting,

hiuting said:

## Homework Statement

The sound level in a noisy classroom is 101 dB. How much energy in J is transmitted to the outside through an open window of height 2 m and width 2.75 m, if the class is 40 minutes long?. What is the decibel rating 1 km from the classroom, assuming sound is distributed equally in all directions?

## Homework Equations

I = P / 4(pi)r2

This is the intensity in some cases, but what is the definition of intensity?
$$\beta$$ = 10log(I/I0)

## The Attempt at a Solution

the answers are [P = 0.069 W; E = 166 J; 46.4 dB]

I tried finding v,

What v are you trying to find, and how did you use the above equations to find it?

but I don't know what the dimensions of the window are for.

## 1. What is sound energy and how is it produced?

Sound energy is a form of energy that is created when an object vibrates and causes particles in the surrounding medium, such as air, to also vibrate. This vibration creates pressure waves that travel through the medium and are perceived by our ears as sound.

## 2. How is sound energy measured?

Sound energy is measured in decibels (dB), which is a logarithmic scale that represents the intensity or loudness of sound. The higher the decibel level, the louder the sound. The scale is based on the threshold of human hearing, with 0 dB being the softest sound that a human can hear.

## 3. What factors affect the intensity of sound energy?

The intensity of sound energy is affected by several factors, including the amplitude of the sound wave (the height of the wave), the distance from the source of the sound, and the medium through which the sound is traveling (e.g. air, water, solids). In general, the closer you are to the source of the sound, the louder it will be.

## 4. How does sound energy relate to pitch?

Sound energy and pitch are related, but they are not the same thing. Pitch is determined by the frequency of a sound wave, which is the number of vibrations or cycles per second. Higher frequency sound waves have a higher pitch, while lower frequency sound waves have a lower pitch. However, the intensity or loudness of the sound can also affect our perception of pitch.

## 5. How does sound energy travel through different mediums?

Sound energy travels through different mediums, such as air, water, and solids, at different speeds. This is due to the density and elasticity of the medium. In general, sound travels fastest through solids, then liquids, and slowest through gases. This is why sound can be heard more clearly underwater than in air.

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