Detecting sound

Just as a vibrating object creates sound, thus forming compression waves in air or some other medium, sound is also detected by the waves causing a back-and-forth vibration of some object in its path.

What is happening is that the sound in traveling from the air into the object, just like you can hear sound going through the walls or windows in your house.

Since the vibrations are so small in most situations, you cannot tell that the object is actually vibrating. However, you can feel how sound can cause other things to vibrate by standing in front of some loudspeakers when music is being played very loud. You can actually feel the vibration on your skin and chest.

Loud sounds in a room can cause the windows and even walls to vibrate noticeably at the frequency of the waveform.

The detection of sound waves requires transferring the vibration it causes into some sort of signal that can be processed and used.

Feeling the vibration of a wall when loud music is being played in the other room is detecting the sound, by changing the vibration into signals to your brain from your sense of touch. But that isn't very useful information.

Your ear or a microphone can convert the vibration into a signal, which can then be processed into a form that can duplicate or reproduce that sound.

The type of signal that the vibration creates is usually an electrical signal. Processing can almost duplicate the original sound, except for some distortions.