When sound waves have a "wah" effect, it typically refers to a particular audio effect known as a wah-wah effect. The wah-wah effect is a modulation effect commonly used in music, particularly in guitar playing. It creates a distinctive sweeping sound that mimics the human voice saying "wah-wah" or "wah."
The wah effect is achieved using a guitar effects pedal called a wah-wah pedal. When the pedal is engaged, it alters the frequency response of the guitar signal in a specific way. By rocking the pedal back and forth with the foot, the player can control the cutoff frequency of a bandpass filter, which emphasizes or attenuates certain frequencies. This sweeping motion produces the characteristic "wah" sound.
The wah effect is often associated with funk, blues, and rock genres, and it can add expressiveness and dynamic movement to guitar solos and rhythm playing. The intensity and speed of the wah effect can be adjusted by the player to create different sonic textures and variations.
In summary, when sound waves have a "wah," it means they exhibit a sweeping modulation effect commonly achieved using a wah-wah pedal, resulting in a distinctive "wah" sound.