Use this calculation for a first-order acoustics estimate when the stated geometry, propagation model, averaging convention, reference quantity, and SI units match the measurement or design problem.

Transmit Megahertz

A finite measured or assumed value greater than or equal to 0, expressed in MHz.

Velocity Meters Per Second

A finite measured or assumed value, expressed in m/s.

Beam Angle Degrees

A finite measured or assumed value greater than or equal to 0, expressed in deg.

Speed Meters Per Second

A finite measured or assumed value greater than or equal to 0, expressed in m/s.

The implemented rule is: Signed pulse-echo Doppler shift 2 f0 v cos(theta)/c for tissue velocity at angle theta.^[1]

Shift Hertz

The calculated shift hertz, expressed in Hz.

This is an idealized calculation rather than a complete acoustic simulation or measurement. Reflections, boundary conditions, directivity, damping, frequency dependence, near-field behavior, background noise, transducer response, temperature, humidity, and geometry can change a real result. The pulse-echo formula depends on the cosine of the beam-flow angle; small angle errors become especially consequential as the angle approaches 90 degrees.

Confirm important results with calibrated measurements or a model that includes the actual geometry, materials, boundaries, source directivity, and frequency-dependent losses. Preserve the reference quantity and weighting whenever a result is expressed in decibels.

• Ultrasound Wavelength Tissue

  Ultrasound wavelength in millimetres from tissue sound speed and transducer frequency in megahertz.

• Pulse Repetition Range Ambiguity

  Maximum unambiguous pulse-echo range c/(2·PRF) for propagation speed and pulse repetition rate.

• Tissue Attenuation Frequency Loss

  Pulse-echo attenuation in dB from a specified tissue coefficient, transducer frequency, and one-way depth.