how putting a glass against an adjoining wall and pressing your ear against it allows you to hear clearer into the other room

Question

how putting a glass against an adjoining wall and pressing your ear against it allows you to hear clearer into the other room

In: 271

Answer 1

Sound travels in a compression wave through matter. It travels faster, and farther through denser matter. i.e. Liquids, and solids, than it does through the air. This is why in the ocean, whales’ calls can be heard hundreds of kilometers away. Also, the low frequencies of these sounds have longer wavelengths, furthering the distance the sound waves can travel.

This being said, in a house, low frequencies are primarily carried through the wall, with the high frequencies more muffled and attenuated. A glass cup is less dense than the wall with a higher natural resonance, and is more prone to carry *high* frequencies. The cup touches the solid wall, you put your ear up to the cup, and you can hear the high and low frequencies of the conversation, thus making it sound clearer than just the lows on their own.

Answer 2

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Answer 3

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Answer 4

The cup seals off ambient noise around your ear while the glass transmits the wall’s vibrations into a now nearly silent and sealed chamber. Movies and TV shows where the character presses the open end of the glass against the door/wall simply fucked up.