Langford Analytic · Knowledge Base
Acoustics, Aeroacoustics & Vibroacoustics
How pressure waves, structural vibration, fluid flow and radiated noise interact — from engineering acoustics fundamentals and sound pressure level through wave propagation, cavity resonance, structural radiation, vibroacoustic coupling, transmission loss and acoustic fatigue to aeroacoustics, numerical methods, Statistical Energy Analysis, hybrid FE–SEA, structural-acoustic power flow, acoustic analogies, beamforming, test correlation and defensible engineering evidence.
Featured
Engineering Acoustics FundamentalsHow pressure fluctuations propagate as sound, why acoustic problems are inherently dynamic, and how the source–path–receiver chain organises every vibroacoustic investigation — from pressure wave and frequency through wavelength, sound speed and the coupling between fluid pressure and structural response.Vibroacoustic CouplingHow structural and acoustic modes interact at shared boundaries, why the vibroacoustic problem is a coupled energy-transfer problem, and the difference between one-way and two-way coupling — the flagship article of the category, connecting pressure fields to structural motion and back.Aeroacoustics FundamentalsHow fluid flow generates sound, the physical mechanisms that distinguish aeroacoustics from ordinary CFD pressure fluctuation, and the source types — turbulence, wakes, separation, vortex shedding, jets and bluff bodies — that engineers must understand.From Noise Source to Defensible Vibroacoustic Engineering EvidenceThe complete chain from source identification through spectrum, transmission path, structural and acoustic modes, receiver response, test, correlation, mitigation and engineering conclusion — the integrating article that connects the category into a single defensible workflow.
Fundamentals
Sound Pressure Level, Decibels & FrequencyHow RMS pressure converts to a logarithmic level, why decibels do not add arithmetically, what the reference pressure means and why it is convention-dependent, and the critical distinction between a 3 dB energy change and a doubling of perceived loudness.Acoustic Waves, Impedance & PropagationHow acoustic waves propagate, reflect, transmit and absorb at boundaries; what acoustic impedance means conceptually; and why the near field and far field of a source behave fundamentally differently — with the engineering implications for how sound reaches a structure.Frequency Spectra, Octave Bands & Signal InterpretationHow a time-domain acoustic signal is transformed into a frequency spectrum, what FFT resolution and PSD mean for engineering assessment, how octave and fractional-octave bands organise spectral data, and why the choice of presentation changes interpretation but not the underlying signal.Acoustic Cavities & ResonanceHow enclosed volumes — cabins, ducts, enclosures, equipment boxes — develop acoustic modes and standing waves, why a cavity resonates at specific frequencies, and how cavity modes interact with structural modes to produce coupled vibroacoustic response.
Structural Acoustics
Acoustic Excitation of StructuresHow a distributed acoustic pressure field loads panels and shells, what spatial coherence means for structural response, and why high-intensity random acoustic environments are a structural design driver — connecting acoustic excitation to the random vibration framework.Structural Vibration & Radiated SoundHow vibrating panels displace surrounding fluid and radiate sound, what radiation efficiency means conceptually, and why high structural vibration does not automatically mean high radiated sound at every frequency — the structural side of the vibroacoustic problem.Transmission Loss, Isolation & DampingHow sound is blocked, isolated and absorbed along the transmission path — the mass law, the roles of stiffness and damping, the distinction between airborne and structure-borne paths, and why no single treatment controls all frequencies.Random Acoustic Loading & Acoustic FatigueHow broadband acoustic pressure becomes a structural fatigue driver, how the PSD and RMS connect to vibration fatigue analysis, and why acoustic noise can become a structural durability problem when it excites flexible panels or components.
Aeroacoustics & Numerical Methods
Propeller, Fan & Rotating-Flow NoiseHow rotating aerodynamic sources produce both tonal and broadband noise, the roles of blade passing frequency, loading noise, thickness noise, wake interaction and installation effects — and why rotating machinery noise is a composite of several distinct mechanisms.Numerical Acoustic Analysis: FEM, BEM & CFD-Based MethodsHow acoustic problems are solved numerically — finite element acoustics, boundary element methods, coupled structural-acoustic FEM, CFD-based aeroacoustic methods and reduced approaches — and why the acoustic mesh must resolve the waves the analysis is expected to predict.Aeroacoustic Source Modelling — Acoustic Analogies, FW-H & Far-Field PredictionHow unsteady CFD is converted into defensible far-field noise predictions using acoustic analogies and Ffowcs Williams–Hawkings formulations, with attention to source surfaces, sampling, moving geometry and installation effects.
Test & Evidence
Acoustic Test, Microphones & CorrelationHow acoustic measurements are made and correlated with predictions — microphone types and placement, anechoic and reverberant environments, calibration, sampling and windowing, and why a microphone result depends strongly on position and environment.Acoustic Arrays, Beamforming & Source LocalisationHow microphone arrays, beamforming and acoustic imaging are used to locate dominant noise sources, separate competing mechanisms and correlate aeroacoustic or vibroacoustic predictions with test evidence.
Advanced Vibroacoustics
Statistical Energy Analysis for High-Frequency VibroacousticsHow Statistical Energy Analysis represents high-frequency vibroacoustic response through subsystem energy, modal density and power exchange when deterministic mode-by-mode prediction is no longer the most credible engineering description.Hybrid FE–SEA & Mid-Frequency Vibroacoustic AnalysisHow deterministic finite-element and statistical-energy descriptions can be coupled when some parts of a vibroacoustic system remain mode-resolved while others have entered a dense, uncertainty-sensitive high-frequency regime.Structural–Acoustic Power Flow, Radiation Efficiency & Sound PowerHow vibrational energy becomes radiated sound, how radiation efficiency and mobility govern that conversion, and how power-based quantities can reveal dominant transfer paths more reliably than vibration amplitude alone.