Neqsim Noise Screening

Noise Screening

Use this skill for public, educational aerodynamic-noise screening of a gas valve or line restriction. It estimates a sound-pressure-level indicator from the mass flow, pressure drop, and density using an open energy-based approach, so an agent can flag a potential noise problem before detailed IEC 60534-8 prediction.

When to Use

• When a user asks whether a gas valve or restriction is likely to be noisy.
• When an agent needs a quick action/high noise flag for screening.
• When examples must run without confidential valve trim or vendor noise data.

Inputs

• mass_flow: gas mass flow in kg/s.
• pressure_drop: pressure drop across the restriction in bar.
• inlet_density: inlet gas density in kg/m3.
• sound_speed: speed of sound in m/s (provide this, or temperature and molar mass).
• specific_heat_ratio: ratio of specific heats k, default 1.3.
• temperature: gas temperature in K (used to estimate sound speed).
• molar_mass: gas molar mass in g/mol (used to estimate sound speed).

Outputs

• vena_contracta_velocity_m_s: estimated velocity at the restriction.
• mach_number: velocity divided by the speed of sound.
• internal_sound_power_level_db: internal sound power level (re 1 pW).
• estimated_spl_1m_dba: screening sound-pressure level at 1 m.
• noise_warning: ok, action, or high.
• assumptions: public assumptions used by the placeholder model.

Engineering Method

The Python class ValveNoiseModel uses a public energy-based aerodynamic-noise approach:

• the vena-contracta velocity uses v = sqrt(2 * dP / rho).
• the speed of sound uses the provided value or c = sqrt(k * R * T / M).
• the mechanical stream power uses W_m = 0.5 * mdot * v^2.
• the acoustic power uses W_a = min(0.01, eta_f * Mach^3) * W_m.
• the sound power level uses L_W = 10 log10(W_a / 1 pW) and a fixed transmission loss converts it to a 1 m sound-pressure level.

This is an educational screening indicator, not a full IEC 60534-8-3 prediction. It uses a generic acoustic efficiency and a fixed transmission loss with no valve style, trim, pipe schedule, distance correction, or frequency weighting. It is not a replacement for validated noise prediction, vendor noise data, and qualified acoustic review.

Python Usage Pattern

from noise_screening import ValveNoiseModel

model = ValveNoiseModel()
result = model.evaluate(
    mass_flow=12.0,
    pressure_drop=40.0,
    inlet_density=35.0,
    temperature=310.0,
    molar_mass=19.0,
)

print(result.mach_number)
print(result.estimated_spl_1m_dba)
print(result.noise_warning)

Related NeqSim Functionality

For validated valve behaviour, redirect to existing NeqSim classes:

• neqsim.process.equipment.valve.ThrottlingValve — flow-vs-Cv valve and pressure-drop response that defines the noise duty.
• neqsim.process.equipment.valve.ControlValve — control valve with characteristic and controller coupling.

Full aerodynamic-noise prediction follows IEC 60534-8-3. This skill is a public noise triage layer that decides when to invoke detailed valve and noise tools.

Validation Checklist

• [ ] Mass flow, pressure drop, and density are positive.
• [ ] Either a sound speed or temperature and molar mass are supplied.
• [ ] The result is treated as a screening indicator, not a certified noise level.
• [ ] Tests cover the basic indicator, a high-noise case, sound-speed estimation, and invalid input.
• [ ] Real noise prediction is redirected to validated tools and qualified acoustic review.

Common Mistakes

| Symptom | Cause | Fix | | --- | --- | --- | | SPL looks too precise | Treated indicator as IEC result | Use it only for screening | | Mach off | Sound speed from wrong gas | Provide molar mass and temperature | | Wrong magnitude | Mass flow in kg/h not kg/s | Use kg/s |

Limitations

• Screening indicator only, not IEC 60534-8-3 prediction.
• No valve style, trim, pipe schedule, or frequency content.
• Fixed transmission loss and generic acoustic efficiency.

References

• NeqSim repository: https://github.com/equinor/neqsim
• NeqSim Skills Guide: https://github.com/equinor/neqsim/blob/master/docs/integration/skills_guide.md

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: equinor
• Source: equinor/neqsim-community-skills
• License: Apache-2.0
• Homepage: https://equinor.github.io/neqsimhome/

Install and usage instructions live in the source repository linked above.