Which unit is used to describe the pitch or tone of sound in the frequency domain?

• A. Hertz (Hz)
• B. Decibels (dB)
• C. Pascals (Pa)
• D. Wavelength (m)

Answer: (A)

When looking at pitch or tone in the frequency domain, the important quantity is how often the waveform repeats each second. That is frequency, and it’s measured in hertz. In a spectrum, the horizontal axis shows frequency in Hz, so a higher pitch appears at higher Hz values and a lower pitch at lower Hz values. This directly ties the perceptual attribute of pitch to the actual frequency content of the signal.

The other units describe different aspects: decibels quantify loudness or level, not which frequencies are present; pascals measure pressure amplitude, which relates to how strong the sound is but not its frequency; wavelength is a spatial concept that depends on frequency but is not the unit used to label frequency components in a spectrum. In audio analysis, Hz is the standard unit for describing the pitch information across the frequency spectrum.