FEA · CFD · NVH · THERMAL · ACOUSTIC — ENGINEERING SIMULATION
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SPEC SHEET S-05 · REV A · UPDATED SEP 2026

S-05 · ACOUSTICS

Is it too loud? Where the noise comes from, and what actually reduces it.

Acoustic analysis of machines, enclosures, vehicles and sites — sound radiated by vibrating structures and flows, transmitted through walls and openings, and predicted at the receivers your limit applies to. Measures are ranked by the decibels they buy.

∇²p − (1/c²) ∂²p/∂t² = 0L_p [dB(A)] at receivervs. limit
Submit a Problem Statement Sample report outline ↓
[✓] NDA before data exchange[✓] Fixed scope & price[✓] Independent internal check
FIG. 1 — Sound radiated from a vibrating source SCHEMATIC wave frontssource
S-05 · AT A GLANCESPEC
TYPICAL SCOPE
Gensets and machinery, enclosures and silencers, HVAC, vehicles, outdoor sites
DELIVERABLE
Signed PDF report, levels per receiver in octave bands, noise maps, ranked measures
LEAD TIME
Agreed in the written scope
ANALYSES
Vibro-acoustic (FEM / BEM) · aeroacoustic sources · transmission loss · outdoor propagation
CONFIDENTIALITY
NDA signed before any file is exchanged
QUALITY
Hand check and measurement comparison where data exists
Get a scoped quote →

01 / WHEN YOU NEED IT

Questions this analysis answers.

Noise problems are decided by one receiver and one frequency band — the neighbour at night, the operator position, the cabin at cruise speed.

We find that receiver and band first, then trace the noise back to the source and path that dominate it, so the money goes to the measure that works.

Q1Will the site meet the noise limit at the nearest neighbour?→ Outdoor propagation, ISO 9613-2
Q2Where does the noise come from — which source, which path?→ Source ranking & path analysis
Q3How much will this enclosure or silencer really give?→ Transmission loss / insertion loss
Q4Why is there a tone at one speed only?→ Vibro-acoustic, with S-03 modes
Q5How loud is the fan or airflow itself?→ Aeroacoustic sources from CFD
Q6Which measure gives the most dB for the money?→ Ranked noise-control measures

02 / DELIVERABLES

What you receive. In writing, before we start.

Each item is listed in the scope document you sign off. Nothing on this list is a surprise at the end.

PDF

Technical report

Scope, limits, sources, assumptions, model, results and conclusions. Signed and revision-controlled.

XLSX · PDF

Levels per receiver

L_p in dB(A) and in octave bands per receiver and operating case, with the limit.

IN REPORT

Noise maps & spectra

Maps, spectra and source contributions that show where the noise comes from.

IN REPORT

Source ranking

Contribution of each source and path to the governing receiver.

APPENDIX

Verification appendix

Mesh per wavelength, free-field hand check, comparison with measurements where available.

IN REPORT

Ranked measures

Silencers, barriers, enclosure upgrades and isolation — with the dB each one buys.

2 H ONLINE

Results review meeting

A walk-through with your engineers. Questions answered and recorded in the final revision.

Revision round

Re-run for design changes within the agreed scope, with a revision log in the report.

03 / METHODS

The right analysis for the question — not the most expensive one.

The method follows the frequency and the path: finite and boundary elements at low and mid frequencies, flow-noise sources from CFD, and standard propagation models outdoors.

FIG. 0 — Standing pressure pattern in a cavity (schematic)
ANALYSISUSE IT WHENKEY OUTPUTTYPICAL REFERENCE
Harmonic acoustics (FEM)Enclosed cavities, cabins, rooms, ducts at low and mid frequencyPressure field, cavity modes, L_p at receivers≥ [6] elements per wavelength
Radiated noise (BEM / FEM)Vibrating surfaces radiating into open spaceRadiated sound power, directivity, L_p at receivers→ velocities from S-03
Vibro-acoustic couplingStructure and fluid influence each other — panels, housingsCoupled response, structure-borne noise→ with S-03 Vibration
Aeroacoustic sourcesFans, vents and jets where the flow makes the noiseSource strength and spectrum→ with S-02 CFD · on request
Transmission lossWalls, enclosures, doors, silencersTL and insertion loss per bandISO 717-1 rating
Outdoor propagationSite noise at neighbours and site boundariesL_p at receivers, noise mapsISO 9613-2
High frequency (SEA)Many modes per band, large structuresBand-averaged levels and energy flow
FIG. 2 — Why dB(A) hides low-frequency noise — A-weightingSCHEMATIC
-26.2 dB -16.2 dB 0 dB +1.0 dB 0 dB 31.5 63 125 250 500 1k 2k 4k 8k 16k frequency [Hz] (log) → A-weighting [dB] A-weighting subtracts 26 dB at 63 Hz and 16 dB at 125 Hz, so an engine or fan tone can dominate annoyance while barely moving the dB(A) total. We report octave bands for that reason.
FIG. 3 — Sound insulation — the mass lawSCHEMATIC
20 40 60 +6 dB per doubling of mass m = 20 kg/m² m = 10 kg/m² mass law · real panels dip at coincidence 125 250 500 1k 2k 4k frequency [Hz] (log) → transmission loss [dB] Doubling a panel's mass buys about 6 dB — and it costs twice the weight. Near the coincidence frequency real panels fall below the line, which the model accounts for.

04 / PROCESS & TIMELINE

From problem statement to signed report.

Five steps, each with a clear hand-off. You always know what we need from you and what you get back.

  1. 012 day

    Scoping call

    FROM YOUProblem statement, drawings, limits
    FROM USNDA, list of questions and missing data
  2. 022 days

    Scope & fixed quote

    FROM YOUSource data, receivers, operating times
    FROM USWritten scope, assumptions, acceptance criteria, price
  3. 037 days

    Model & solve

    FROM YOUCAD, site plan, material build-ups
    FROM USInterim check-in: source ranking and first levels
  4. 042 days

    Verify & measures

    FROM YOUMeasured data if available
    FROM USVerification, ranked measures, second-engineer review
  5. 052 days

    Report & review

    FROM YOUYour comments on the draft
    FROM USSigned report, files, review meeting

05 / INPUTS

What we need from you.

REQUIRED
  • [✓]Geometry — STEP / IGES / Parasolid, or dimensioned drawings; site plan for outdoor studies
  • [✓]Sources — sound power in octave bands, or vibration / flow data to derive it
  • [✓]Materials — panel build-ups, absorbers, seals
  • [✓]Receivers — positions, heights and operating times (day / night)
  • [✓]Noise limits and the standard or permit they come from
  • [✓]The decision the result feeds, and the deadline
HELPFUL IF AVAILABLE
  • [+]Measured sound levels or spectra
  • [+]Supplier noise data for fans, engines and silencers
  • [+]Vibration measurements on the source
  • [+]Complaints or permit conditions
  • [+]Comments from your customer or approver
INCOMPLETE DATA?Most projects start that way.We list what's missing in the scoping call. Anything we have to assume is recorded in the report's assumption register — never hidden in the model.

06 / THE REPORT

See the report before you buy it.

A signed, revision-controlled report of 60 pages on average. Every level at a receiver is traced to its sources, their sound power data and the propagation or insulation model used — in octave bands, not only in dB(A).

  1. T1
    Assumption registerEvery assumption — above all source sound power and absorption — numbered and justified.
  2. T2
    Source traceabilityEach source names its sound power data and where it comes from, in octave bands.
  3. T3
    Verification evidenceMesh per wavelength, free-field hand check and measurement comparison — included.
  4. T4
    Reproducible modelSolver, version, frequency range, material data and propagation settings are stated.
  5. T5
    Plain-language conclusionOne page a manager can read: meets the limit or not, by how much, and what to do.

07 / APPLICATIONS

Typical sources and installations.

Gensets & power plantsExhaust · intake · enclosure · site noise
Machinery & compressorsRadiated noise · tones · operator position
HVAC & data centersFans · chillers · rooftop plant
VehiclesCabin noise · structure-borne paths
Rail vehiclesInterior noise · equipment enclosures
Buildings & sitesFaçade insulation · plant rooms · boundaries
MarineEngine rooms · accommodation noise
Products & appliancesDeclared noise emission · tonal content

08 / STANDARDS

Checked to the clause your approver reads.

Limits, measurement conditions and prediction methods come from the standard or permit that applies to your product or site — cited in the report.

STANDARDWHAT WE USE IT FOR
ISO 9613-2Attenuation of sound during outdoor propagation
ISO 3744Sound power from sound pressure — engineering method
ISO 717-1Rating of airborne sound insulation
EN ISO 12354Building acoustics — prediction from element performance
IEC 61672-1Sound level meters — frequency weightings (A, C)
Directive 2000/14/ECNoise emission of outdoor equipment

09 / HOW TO ENGAGE

Three ways to work with us.

Prices are fixed per written scope. You pay for the answer to a defined question, not for open-ended hours.

E-01PROJECT

Fixed-scope project

BEST FOR
A defined part or structure with a clear question
PRICE
Fixed quote after scoping
Start with a problem statement
E-02RETAINER

Engineering retainer

BEST FOR
Design teams with recurring analysis needs
PRICE
Quoted per scope
Discuss a retainer
E-03REVIEW

Third-party review

BEST FOR
Checking an FEA or hand calculation done by someone else
PRICE
Fixed quote
Request a review

10 / FAQ

Asked before every project.

Something else? Ask it in the problem statement — the answer comes with the scope.

Which software do you use?

Tessera — the solver we build — runs the free calculators on this site today, each published with its reference cases. For project work the solver is chosen against the standard the result must satisfy, and named in the written scope. Every report states the solver, version, frequency range and propagation settings.

We only have a dB(A) figure for the source. Is that enough?

For a first estimate, yes. For measures that work, we need octave bands — we derive them from supplier data, measurements or a vibration model and state which.

Can you predict tones, not only totals?

Yes. Tones come from rotating parts and structural or cavity modes; we find the mode behind the tone together with S-03 Vibration.

Do you also measure?

All measurements are performed by our team using calibrated, industry-standard measurement equipment, following a defined measurement protocol. We use your measurements to calibrate the model and report the comparison.

Will the result hold up with the permitting authority?

The method and limits are taken from the standard or permit that applies, and every assumption is listed — so the report can be checked line by line.

How is the price set?

Per written scope: number of sources and receivers, frequency range, and whether vibro-acoustic or aeroacoustic modelling is needed.

RELATED CAPABILITIESAll services →
S-01 · STRUCTURAL Structural / FEA σ_vM ≤ f_y / γ_M0 Spec sheet →
S-02 · FLUID CFD ∇·(ρuu) = −∇p + ∇·τ Spec sheet →
S-03 · DYNAMICS NVH & Dynamics [K − ω²M]{φ} = 0 Spec sheet →
S-04 · THERMAL Thermal ρc_p ∂T/∂t = ∇·(k∇T) + q Spec sheet →
S-06 · CONCEPT Concept & Design min f(x) s.t. g(x) ≤ 0 Spec sheet →

11 / PROBLEM STATEMENT

Send the noise limit. Get a written scope back.

Tell us what makes the noise, who hears it and which limit applies. We reply with questions or a fixed scope.

  • [✓] NDA before data exchange
  • [✓] Response within 2 business day(s)
  • [✓] Scope, assumptions & acceptance criteria in writing