Sound hitting a wall

[GomerPyle]

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Which of the following explains why the intensity of the sound heard is less when a wall is placed between the source and the listener?

The answer is because part of the sound is reflected off the solid. But it says the listener hears less sound, but at the same frequency and wavelength.

I understand that the sound will remain the same frequency, since all ways remain at the same frequency once they are made. Velocity also remains constant unless it changes medium. In this case, the sound moving through solid should move faster (since sound moves faster in thicker mediums) and because it is at the same frequency, the wavelength should also increase. I don't understand why the answer says the observer hears the sound at the same wavelength...

 

[FeinMS]

Unless the listener is planted in the wall, the sound will enter and leave the wall going back to the same f and wavelength.

 

[GomerPyle]

Unless the listener is planted in the wall, the sound will enter and leave the wall going back to the same f and wavelength.

Lol makes sense, but the sound inside the wall doesn't have the same wavelength...only when it leaves the wall again with the same velocity it had before hitting the wall does it have the same wavelength....correct?

 

[FeinMS]

Yes that's what I think.

 

[gettheleadout]

Lol makes sense, but the sound inside the wall doesn't have the same wavelength...only when it leaves the wall again with the same velocity it had before hitting the wall does it have the same wavelength....correct?

Correct.

 

[jtran7]

The speed of the sound wave depends on the density of the material, more dense means more molecules closer together allowing the wave to travel faster through denser materials. This results in f staying the same but speed of wave in the wall increasing therefore the wavelength changes. But as the wave leaves the wall and travels through air, the density decreases so the speed of the wave travels slower and the wavelength returns on the original value

 

[GomerPyle]

THANKS. From the question I had assumed that the observer had his ear pressed against the wall and was hearing what was inside the wall rather than the sound that returned to air and then to his ear.

 

[gettheleadout]

THANKS. From the question I had assumed that the observer had his ear pressed against the wall and was hearing what was inside the wall rather than the sound that returned to air and then to his ear.

Actually, it would regardless, since he can't really pull his eardrum out through his ear canal and press it to the wall; even with his outer ear pressed against the wall the sound would still return to air within the ear canal before hitting his eardrum.