Which of the following is NOT one of the seven acoustic parameters used to describe a sound wave?

• A. Period
• B. Frequency
• C. Doppler shift
• D. Amplitude

Answer: (C)

Doppler shift is about how motion between the source and observer changes the frequency that is perceived, not about a property of the sound wave itself. A sound wave is described by intrinsic, frame‑invariant characteristics such as period (the time for one cycle), frequency (cycles per second), wavelength, velocity, amplitude (how big the pressure variation is), and phase. These describe the waveform as it exists in the medium. The seven acoustic parameters referenced are describing those inherent features of the wave, not effects caused by relative motion. So Doppler shift isn’t one of the fundamental descriptors of the waveform, making it the correct choice. The other options—period, frequency, and amplitude—are standard intrinsic properties that define the wave itself.