Most people think their recorded voice sounds higher or thinner than the voice they hear while speaking. The recording is not necessarily changing your voice; your normal listening experience is different. When other people hear you, sound travels mainly through the air from your mouth to their ears. You hear that route too, but vibrations also travel through the bones and tissues of your head to your inner ear. Bone conduction changes the mixture of frequencies that reaches you and often makes your own voice seem deeper. A microphone mainly captures the sound travelling through the air. A recording therefore gives you something closer to the version of your voice that other people hear.

The same physics matters in theatres, classrooms, studios and hospitals. Designers choose shapes and materials to control reflections and unwanted sound, while engineers use microphones and signal processing to measure or deliberately alter waves.

Waves transfer energy and information without transferring matter from source to receiver overall. Frequency tells us how many oscillations pass each second, wavelength is the spacing between matching points, and wave speed links them through v = fλ. Different frequencies interact with materials differently, which is why engineers can choose particular parts of the electromagnetic spectrum—or particular sound frequencies—for sensing, communication, heating or imaging.