In acoustics, which option is not a valid unit for wavelength?

In acoustics, which option is not a valid unit for wavelength?

• A. Feet per cycle
• B. Meters per cycle
• C. Cycles per second
• D. Seconds per cycle

Answer: (D)

Wavelength is the distance the wave travels in one complete cycle, so its units must express length per cycle. That’s why meters per cycle or feet per cycle are valid—each describes a distance covered per cycle. The relationship λ = v / f also shows this: meters per second divided by cycles per second gives meters per cycle, tying the concept to a concrete unit. Seconds per cycle measures how long one cycle lasts (the period), which is a time quantity, not a length. Cycles per second describes how many cycles occur each second (frequency), a rate rather than a distance. While frequency relates to wavelength through the speed of sound, these are not units of wavelength themselves. Therefore, seconds per cycle is not a valid unit for wavelength.

Wavelength is the distance the wave travels in one complete cycle, so its units must express length per cycle. That’s why meters per cycle or feet per cycle are valid—each describes a distance covered per cycle. The relationship λ = v / f also shows this: meters per second divided by cycles per second gives meters per cycle, tying the concept to a concrete unit.

Seconds per cycle measures how long one cycle lasts (the period), which is a time quantity, not a length. Cycles per second describes how many cycles occur each second (frequency), a rate rather than a distance. While frequency relates to wavelength through the speed of sound, these are not units of wavelength themselves. Therefore, seconds per cycle is not a valid unit for wavelength.