How can a single speaker, such as earphones, produce highs and lows at the same time
In: Technology
Soundwaves of different sizes combine, just like waves in water. Small short waves (high frequencies) can exist as parts of bigger long waves (low frequencies).
What your eardrum picks up
is the resulting combined wave pattern of all the sound sources around you. The brain does all the work of breaking the signal back down into individual sounds from different locations.
When you are playing back a recording, what the speaker does is really just repeat the air vibration pattern that the microphone was subjected to.
I love this old educational film and its animations, I think it explains the concept well:
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