Change in frequency or pitch when a sound source moves toward or away from the listener is known as what?

Change in frequency or pitch when a sound source moves toward or away from the listener is known as what?

• A. Doppler effect
• B. Diffraction
• C. Reflection
• D. Interference

Answer: (A)

Change in frequency or pitch when a sound source moves toward or away from the listener is caused by the Doppler effect. When the source approaches, the sound waves are compressed, increasing frequency so the pitch sounds higher. When the source moves away, the waves are stretched, decreasing frequency so the pitch sounds lower. The emitted frequency from the source doesn’t change; what changes is how often those waves reach the listener due to relative motion and the speed of sound in the medium. A familiar example is a siren that sounds higher as it comes toward you and lower as it moves away. The other phenomena don’t explain this pitch shift: diffraction involves waves bending around objects, reflection is bouncing off surfaces, and interference is the combo of overlapping waves creating patterns, not a simple change in pitch from motion.

Change in frequency or pitch when a sound source moves toward or away from the listener is caused by the Doppler effect. When the source approaches, the sound waves are compressed, increasing frequency so the pitch sounds higher. When the source moves away, the waves are stretched, decreasing frequency so the pitch sounds lower. The emitted frequency from the source doesn’t change; what changes is how often those waves reach the listener due to relative motion and the speed of sound in the medium. A familiar example is a siren that sounds higher as it comes toward you and lower as it moves away. The other phenomena don’t explain this pitch shift: diffraction involves waves bending around objects, reflection is bouncing off surfaces, and interference is the combo of overlapping waves creating patterns, not a simple change in pitch from motion.