Amplitude
Explanation
Sound waves are longitudinal mechanical waves characterized by physical properties such as frequency, amplitude, speed, and wavelength. These physical properties determine the physiological perception of sound, specifically its pitch, loudness, and quality (timbre).
Detailed Analysis:
- Amplitude (Loudness): Loudness is the measure of the sound energy reaching the ear per second. It is primarily determined by the amplitude of the sound wave. The loudness of a sound is proportional to the square of the amplitude of the vibration produced ($L \propto A^2$). Greater amplitude results in a louder sound, while smaller amplitude results in a feeble sound.
- Frequency (Pitch): Frequency determines the pitch or shrillness of a sound. A higher frequency corresponds to a higher pitch (e.g., a woman's voice), while a lower frequency corresponds to a lower pitch (e.g., a man's voice).
- Speed: The speed of sound is determined by the properties of the medium (density and elasticity) through which it travels. It does not determine the loudness.
- Wavelength: Wavelength is the distance between two consecutive compressions or rarefactions. While related to frequency and speed ($v = f \lambda$), it is not the primary factor determining loudness.
Key Takeaway:
Loudness depends on the amplitude of the sound wave, whereas pitch depends on the frequency.