The correct answer is option 1: dB.

Sound waves are typically measured in units of frequency, which represents the number of cycles or vibrations per unit of time. The frequency of a sound wave is often measured in hertz (Hz), which represents the number of cycles per second.

Option 1, dB, stands for decibels. Decibels are not used to measure the frequency of a sound wave, but rather the intensity or loudness of a sound. Decibels provide a relative measure of the sound`s intensity compared to a reference level.

Option 2, s-1, is also a valid unit for measuring the frequency of a sound wave. It represents cycles per second, similar to Hz.

Option 3, Hz, is the standard unit for measuring the frequency of a sound wave. It represents the number of cycles or vibrations per second.

Option 4, min-1, represents a unit of frequency as well, but it is not commonly used in the context of sound waves. It represents the number of cycles or events per minute.

To summarize, while options 2, 3, and 4 can be units of frequency for a sound wave, option 1 (dB) is not a valid unit