Is spatial pulse length equal to the product of wavelength and the number of cycles in the pulse?

• A. False
• B. True
• C. Sometimes
• D. Not defined

Answer: (B)

Spatial pulse length is the distance a ultrasound pulse travels in space. Each cycle spans one wavelength, so the total length of the pulse is the number of cycles in the pulse times the wavelength. In other words, SPL = number of cycles × wavelength. Since wavelength equals the speed of sound in the medium divided by the frequency (λ = c/f), SPL can also be written as SPL = n × c / f. This shows how the pulse’s length depends on how many cycles you emit and the medium’s properties. For a given transducer and medium, more cycles mean a longer SPL, while fewer cycles mean a shorter SPL.