Increasing the frequency on a multifrequency transducer from 3.5 MHz to 5.0 MHz will:

Increasing the frequency on a multifrequency transducer from 3.5 MHz to 5.0 MHz will:

• A. Increase the sound propagation speed
• B. Increase the pulse length
• C. Increase penetration
• D. Decrease the wavelength

Answer: (D)

Wavelength is determined by the speed of sound in the medium and the frequency of the wave, through the relation λ = c / f. In soft tissue, the speed of sound is essentially constant (about 1540 m/s), so increasing the frequency directly lowers the wavelength. For example, going from 3.5 MHz to 5.0 MHz shortens the wavelength from roughly 0.44 mm to about 0.31 mm. The sound speed does not increase with frequency, so that option isn’t correct. Higher frequency also experiences greater attenuation, which reduces penetration rather than increases it, so that choice isn’t correct either. Regarding pulse length, it is tied to the number of cycles and the wavelength; with a higher frequency, the wavelength is shorter, so the spatial pulse length typically does not increase and often decreases. Thus, the result of increasing the frequency is a shorter wavelength.

Wavelength is determined by the speed of sound in the medium and the frequency of the wave, through the relation λ = c / f. In soft tissue, the speed of sound is essentially constant (about 1540 m/s), so increasing the frequency directly lowers the wavelength. For example, going from 3.5 MHz to 5.0 MHz shortens the wavelength from roughly 0.44 mm to about 0.31 mm.

The sound speed does not increase with frequency, so that option isn’t correct. Higher frequency also experiences greater attenuation, which reduces penetration rather than increases it, so that choice isn’t correct either. Regarding pulse length, it is tied to the number of cycles and the wavelength; with a higher frequency, the wavelength is shorter, so the spatial pulse length typically does not increase and often decreases.

Thus, the result of increasing the frequency is a shorter wavelength.