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.

Neck Area Square Meters

A finite measured or assumed value greater than or equal to 0, expressed in m2.

Cavity Cubic Meters

A finite measured or assumed value greater than or equal to 0, expressed in m3.

Effective Neck Meters

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

The implemented rule is: Lumped Helmholtz resonator frequency from sound speed, neck area, cavity volume and effective neck length.^[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.

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.

• Helmholtz Port Length

  Physical Helmholtz neck length required for a target resonance, subtracting a supplied total end correction.

• Pipe End Correction

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