| The transfer of energy among molecules creates a mechanical wave of energy called a sound wave, which propagates away from the source of the disturbance. |
| To take the simplest example, consider a sound wave hitting the device directly from above. |
| This phenomenon involves the bending of a sound wave owing to changes in the wave's speed. |
| We hear different sounds because of variations in the sound wave frequency. |
| This is important because a long wavelength means that the sound wave can pass around barriers, like rocks, easily. |
| And instead of the stylus making a groove that varied in depth, the stylus moved laterally, zigzagging with changes in the sound wave. |
