When sound waves interfere and result in a quieter sound, it is called destructive interference. Destructive interference occurs when two or more sound waves combine in such a way that the crests of one wave align with the troughs of another wave, or vice versa. As a result, the amplitudes of the waves subtract or cancel each other out, leading to a reduction in the overall intensity or loudness of the sound.
Destructive interference can occur when two sound waves of equal frequency and amplitude meet each other with a phase difference of 180 degrees (or π radians). The waves effectively "cancel" each other, leading to a decrease in the net amplitude and a quieter sound.
This phenomenon of destructive interference is observed in various situations, such as when sound waves reflect and interfere with each other, or when multiple sources produce sound waves that interact. Understanding and manipulating destructive interference is important in fields like acoustics and audio engineering, as it can be used to control sound quality, reduce unwanted noise, or create specific sound patterns.