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.

Sound Speed Meters Per Second

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

Length Meters

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

The implemented rule is: Ideal first resonance of a pipe open at both ends, neglecting end corrections.^[1]

Frequency Hertz

The calculated frequency 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 ideal resonance omits end correction, losses, bore shape, dispersion, and higher-mode effects unless an effective length is supplied separately.

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.

• Stopped Pipe Fundamental

  Ideal first resonance of a pipe stopped at one end, neglecting end corrections.

• Pipe End Correction

  Approximate unflanged open-pipe end correction 0.61 times the pipe radius, per open end.

• Half Wave Resonator Length

  Ideal half-wave resonator length from sound speed and fundamental frequency, before end correction.