1. Increased String Vibration: Plucking the string with more force causes it to vibrate more vigorously. The greater the amplitude of the vibration, the louder the sound produced.
2. Enhanced Sound Radiation: The increased string vibration results in more efficient sound radiation. The vibrating string transfers its energy to the surrounding air, creating sound waves. Plucking the string harder generates stronger sound waves, leading to a louder sound.
3. Harmonic Excitation: Plucking the string with more force can excite additional harmonics or overtones. Harmonics are frequencies that are multiples of the fundamental frequency of the string. These harmonics add richness and complexity to the sound, making it louder and fuller.
4. Increased Sound Pressure: The combination of increased string vibration, enhanced sound radiation, and harmonic excitation results in a higher sound pressure level. Sound pressure is the measure of the force exerted by sound waves on the eardrum. The higher the sound pressure, the louder the sound perceived by the listener.
5. Resonance: Banjos have a natural resonant frequency determined by the length, tension, and mass of the strings and the characteristics of the banjo's body. Plucking the string with force can excite this resonant frequency, causing the banjo's body to vibrate sympathetically. This sympathetic vibration reinforces the sound produced by the string, making it louder.
Therefore, plucking a banjo string hard increases the amplitude of vibration, enhances sound radiation, excites harmonics, and stimulates the banjo's resonance, resulting in a louder sound.