Infographics / Ultrasound Physics

Fundamental ultrasound wave properties

Top: a band of vertical lines that bunch into compressions and spread into rarefactions, with an aligned pressure-versus-distance sine curve whose peaks sit under compressions and troughs under rarefactions; the wavelength is marked between two peaks and the amplitude from the midline to a peak, with an arrow showing the direction of wave travel. Middle: the relations c equals f times lambda (wave speed equals frequency times wavelength), period T equals one over f, and c is about 1540 metres per second in soft tissue. Bottom: a logarithmic frequency axis showing the audible band 20 hertz to 20 kilohertz, the ultrasound region above 20 kilohertz, and the diagnostic ultrasound band 2 to 15 megahertz highlighted.

Ultrasound as a longitudinal wave: compressions and rarefactions, c = f lambda, and the diagnostic frequency range Top: a band of vertical lines that bunch into compressions and spread into rarefactions, with an aligned pressure-versus-distance sine curve whose peaks sit under compressions and troughs under rarefactions; the wavelength is marked between two peaks and the amplitude from the midline to a peak, with an arrow showing the direction of wave travel. Middle: the relations c equals f times lambda (wave speed equals frequency times wavelength), period T equals one over f, and c is about 1540 metres per second in soft tissue. Bottom: a logarithmic frequency axis showing the audible band 20 hertz to 20 kilohertz, the ultrasound region above 20 kilohertz, and the diagnostic ultrasound band 2 to 15 megahertz highlighted. Ultrasound is a longitudinal (compression) wave compression rarefaction λ = wavelength mean pressure amplitude pressure direction of wave travel (distance) c = f · λ speed = frequency × wavelength T = 1 / f  (period) c ≈ 1540 m/s in soft tissue Frequency: diagnostic ultrasound sits well above audible sound frequency (log scale) 20 Hz 20 kHz 2 MHz 15 MHz diagnostic 2–15 MHz audible (20 Hz – 20 kHz) ultrasound (> 20 kHz)
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