Sharper detail. Weaker deep echoes.
Change frequency and target depth. See how a shorter pulse helps separate two reflectors, while greater attenuation weakens their returning echoes.
Explore the compromise
Where are the targets?
Follow the depth overview into the enlarged pair: target A is shallower and target B is deeper. Both are always present.
Enlarged simulated image
Same vertical scale as the enlarged pair. A and B at the right edge mark true positions, even if their echoes merge or disappear.
Frequency changes both detail and echo strength. With three cycles per pulse, increasing frequency shortens the wavelength and spatial pulse length, improving axial resolution. In this tissue model it also increases attenuation, so deeper echoes become weaker.
Try this: Choose shallow targets and increase frequency. Then choose deep targets and repeat. Can you find a frequency that separates the targets while keeping their echoes visible?
Show explanation
At low frequency, the two targets may merge because the pulse is long. At high frequency, their echoes may be well separated in principle but too weak to appear on this display. The useful compromise depends on depth and the detail you need to resolve. Untick attenuation to see that weak echoes and overlapping echoes are different limitations.
Teaching model: two equal point reflectors in uniform tissue, sound speed 1540 m/s, three cycles per pulse and assumed attenuation 0.5 dB/cm/MHz. Axial resolution is estimated as half the spatial pulse length. Smooth Gaussian echo responses illustrate overlap. The image uses fixed gain, logarithmic brightness mapping and a 60 dB display range; it has no time-gain compensation, noise, speckle or interference. The display limit is an illustrative setting, not a clinical penetration threshold. A/B position labels are guides, not detected echoes. The loss and amplitude readouts use the centre depth of the pair. Lateral response is held constant to isolate axial resolution.