Which one of the following cannot be the unit of freency of a sound wave?

Frequency is defined as the number of waves or cycles passing a given point per unit of time. The standard SI unit for frequency is the Hertz (Hz), which is equivalent to one cycle per second (s⁻¹) [1]. Since frequency is a rate of occurrence over time, any unit representing 'per unit time' (such as min⁻¹ or s⁻¹) can technically function as a unit of frequency, though Hz is the conventional choice for sound. In contrast, the decibel (dB) is a logarithmic unit used to measure the intensity, amplitude, or loudness of a sound wave rather than its frequency. While frequency determines the pitch of a sound, the decibel scale describes the power or pressure level of the wave. Therefore, dB cannot be used as a unit of frequency.

Sources

1. [1] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 13: Movements of Ocean Water > Characteristics of Waves > p. 109