What does a decibel (dB) measure?

A decibel (dB) is a unit that measures sound intensity based on a logarithmic scale, specifically quantifying the ratio of two sound intensities. This measurement allows for a comparison between the intensity of a sound and a reference level, which is crucial in the context of ultrasound.

In sonography, understanding the decibel scale is essential for interpreting the strength of echoes reflected from tissues. The logarithmic nature of the decibel scale means that a small increase in decibels corresponds to a significant change in intensity, which is important for distinguishing between varying levels of tissue responses in imaging.

The other options, while related to aspects of sound, do not define the decibel accurately. Amplitude refers to the strength or magnitude of the sound wave, while frequency measures the number of cycles per second of a wave. Time taken for sound to travel relates to propagation speed, which is a separate concept from intensity measurements. Therefore, understanding that the decibel represents a ratio of sound intensities is key to applying this knowledge effectively in the field of sonography.