Why does the intensity of sound decrease with distance?

Answer 1

Short Answer:

Sound is quieter with increased distance from its source due to dispersion and inelastic collisions between air molecules.

Long Answer:

To understand an explanation to your answer, you must first understand two important concepts.

First, sound is simply a tiny increase or decrease in air pressure that is produced by some source (such as our vocal cords). This pressure change is sensed by our ears and interpreted by the brain as sound. The amount of pressure change associated with sound is referred to as the acoustic pressure. Loud sounds correspond with large acoustic pressures while source sounds correspond with small acoustic pressures.

Second, sound is an acoustic pressure wave. We can conceive this wave by considering a surface wave produced by a pebble dropped in a pool of water. The wave's height, referred to as the amplitude, will be proportional to the speed of the pebble as it impacts the water. This is because part of the pebble's kinetic energy (energy of motion, proportional to speed) is converted to wave energy. Waves with more energy have greater size amplitude. The same idea can be applied to acoustic waves. If the sound source is high energy (let's say a jet engine), then the amplitude of the pressure wave will be large compared to a low energy source (let's say a human voice). Our brain simply perceives the jet engine as loud and the human voice as quiet.

Now, sound waves expand radially and spherically from their source, just like a surface wave moves outwardly like the purely-circular ring from the pebble's point of impact. All of the energy from the sound source is distributed equally around the circumference of this "wave sphere." The area begins small so energy is densely packed and the amplitude is large. As time passes and the wave moves further away from its source, the area of the wave-front increases while total energy remains the same. This means that the wave's energy is spread more thinly across the area. The result of this decrease in energy density and a corresponding decrease in amplitude; and because it is by area, the attenuation is by square-law (double the radius, quarter the amplitude.. This phenomenon is referred to as dispersion or spreading-loss, and is why we perceive sound as "quieter" when we are far from the source.

Answer 2

Sound energy goes out in all directions. The farther it goes, the greater area it covers, so the energy gets spread out more. That is why it gets weaker.

Answer 3

because the sound has to travel a longer distance, and is then absorbed by other objects around it

Answer 4

Because some gets caught up in the atmosphere and the surroundings, it's called attenuation.

Answer 5

Sounds get quieter when you are further away because the energy in the sound-wave is spread more and more thinly over the surface of an expanding spherical arc.

Answer 6

Because the object creating the sound is in the same place. Whilst your moving away it'll become fainter because the volume is not increasing or decreasing.

Answer 7

The further away you are from a source of sound the softer it is. This is because the sound has had to travel further.

Answer 8

i would have to say because a person/animal can only hear so well and only from a limited distance, therefore a noise further away is harder to hear.

Answer 9

O my giddy giddy gosh ur tapped