How is loudness amplitude changed on a piano?

On a piano, the loudness or amplitude of the sound produced is primarily controlled by two factors: 1. Key Strike Velocity: When a piano key is pressed, it moves a hammer which then strikes the corresponding string(s). The force with which the key is struck determines the velocity of the hammer's movement and the strength of its impact on the string. The faster the hammer strikes the string, the greater the string's vibration amplitude, resulting in a louder sound. Conversely, a softer keystroke produces a more gentle hammer strike, causing the string to vibrate with a smaller amplitude and thus creating a quieter sound. 2. Sustain Pedal (Damper Pedal): The sustain pedal, commonly known as the "loud" pedal, plays a crucial role in changing the piano's overall loudness and sustaining sound. Pressing the sustain pedal lifts the dampers from the strings, allowing them to continue vibrating freely rather than being dampened. Consequently, when a pianist plays notes while holding down the pedal, these notes will not only sound longer but also have a noticeably increased resonance and amplitude. This creates a "louder" or more sustained effect across multiple notes being played simultaneously. Releasing the sustain pedal returns the dampers to their default position, damping the strings and ending the sustained sound. In summary, on a piano, the loudness amplitude can be changed by varying the force or velocity of the keystrokes and through the effective use of the sustain pedal.