How is L_p,1m calculated?

L_p,1m ≈ L_wA − ΔL_TL − RAD with corrections for upstream pressure and pipe diameter. W_a = η_a · ½ ṁ U_v² and ΔL_TL = 17 log10(t_w/D_i) + 36.

Gas vs liquid — which IEC part applies?

Gas → aerodynamic IEC 60534-8-3. Liquid → hydrodynamic IEC 60534-8-4 (cavitation / flashing proxies from ΔP/P1).

When is OEM data required?

Multi-stage low-noise trims, quiet plates, and diffuser silencers are outside this single-stage screening — use manufacturer attenuation tables.

ISA 75.01 Control Valve Noise Prediction Calculator

1. Formula & conversion factors

ANSI/ISA-75.01.01-2012 (IEC 60534-2-1 Mod) — Flow capacity equations · IEC 60534-8-3 — Aerodynamic noise prediction method · IEC 60534-8-4 — Hydrodynamic noise prediction method · ASME B36.10M / B36.19M — Downstream pipe ID and wall

L_p,1m ≈ L_wA − ΔL_TL − RAD

W_a = η_a · W_m · W_m = ½ · ṁ · U_v²

ΔL_TL = 17 log₁₀(t_w/D_i) + 36

IEC 60534-8-3 aerodynamic · IEC 60534-8-4 hydrodynamic · ISA-75.01.01 process context

Hero L_p,1m dBAGas IEC 60534-8-3Liquid IEC 60534-8-4Wall ΔL_TL

Screening prediction of A-weighted sound pressure at 1 m from the downstream pipe for standard single-stage globe/butterfly trims. Acoustic power comes from jet mechanical power with regime-based acoustic efficiency; pipe-wall transmission loss uses t_w/D_i. Multi-stage low-noise trims need OEM attenuation tables.

L_p,1m (External sound pressure level) — Predicted A-weighted level at 1 m from the downstream pipe wall (dBA).
W_a (Acoustic power) — Sound power radiated by the valve trim (W).
W_m (Mechanical jet power) — ½ · ṁ · U_v² stream power at the vena contracta (W).
U_v (Vena contracta velocity) — Jet velocity from isentropic expansion (gas) or Bernoulli (liquid).
ΔL_TL (Pipe transmission loss) — 17 log10(t_w/D_i) + 36 from downstream wall and ID.
η_a (Acoustic efficiency) — W_a / W_m — regime-dependent screening factor.

2. Quick reference lookup table

Default screening duty (NPS 4 Sch 40 · gas · Cv 120)
Quantity	Value	Unit	Notes
P1 / P2	10 / 2	bar g	Gauge upstream / downstream
Mass flow	15 000	kg/h	Air / N₂-like gas
D_i / t_w	102.26 / 6.02	mm	B36 Sch 40
L_p,1m	≈ 84.6	dBA	Safe band (< 85 dBA)

Values are FEK IEC-style single-stage screening results. Manufacturer multi-stage or silencer packages override these levels.

3. How to use this calculator

1
Select downstream NPS and schedule
Wall thickness and ID set pipe transmission loss ΔL_TL.
2
Choose gas or liquid
Gas uses IEC 60534-8-3 aerodynamic path; liquid uses 8-4 hydrodynamic cavitation screening.
3
Enter Cv, P1/P2, temperature, and mass flow
Process conditions drive jet velocity, mechanical power, and acoustic efficiency.
4
Read L_p,1m and severity
Hero shows dBA with Safe / Caution / High badges; rows list W_a, ΔL_TL, U_v, Mach, and exposure time.

4. Engineering FAQ

A screening estimate of external A-weighted sound pressure near the downstream pipe using ISA-75.01 process context and IEC 60534-8-3 / 8-4 acoustic methods for standard single-stage trims.