Common terms used throughout Deepsona and its documentation.
| Term | Definition |
|---|---|
| NVH | Noise, Vibration and Harshness — the engineering discipline covering sound and vibration behaviour of products. |
| SPL | Sound Pressure Level, in decibels referenced to 20 µPa (2×10⁻⁵ Pa). |
| dB | Decibel — a logarithmic ratio. For pressure, level = 20·log₁₀(p / p_ref); for power quantities, 10·log₁₀. |
| RMS | Root Mean Square — the effective (energy-equivalent) amplitude of a signal. |
| A-weighting | A frequency weighting that approximates the ear's sensitivity, used for environmental and product noise (dB(A)). |
| Tacho / RPM | A tachometer pulse or encoder signal giving rotational speed, used to synchronise order analysis. |
| Term | Definition |
|---|---|
| FFT | Fast Fourier Transform — converts a time signal into its frequency spectrum. |
| PSD | Power Spectral Density — spectrum normalised per unit bandwidth (per Hz), for random signals. |
| ENBW | Equivalent Noise Bandwidth — the effective bandwidth of a window function, needed for correct level scaling. |
| Order | A multiple of the rotational frequency. Order 1 tracks the shaft speed; higher orders track gear, blade, or cylinder events. |
| Campbell diagram | A spectrogram of frequency vs. RPM, highlighting order lines and resonance crossings. |
| Coherence | A 0–1 measure of the linear relationship between two signals at each frequency. |
| FRF | Frequency Response Function — the transfer function between an input (force) and output (response). |
| Term | Definition |
|---|---|
| Loudness | Perceived magnitude of sound (sone), per ISO 532. Accounts for masking across critical bands. |
| Sharpness | Perceived spectral balance (acum) — how much high-frequency energy dominates (DIN 45692). |
| Roughness | Sensation caused by fast (~70 Hz) amplitude modulation (asper). |
| Fluctuation Strength | Sensation caused by slow (~4 Hz) amplitude modulation (vacil). |
| Tonality | The degree to which discrete tones stand out of a broadband noise (e.g. TNR, Prominence Ratio). |
| Bark | The critical-band frequency scale used by psychoacoustic models. |
| Term | Definition |
|---|---|
| EMA | Experimental Modal Analysis — identifies modes from measured FRFs (impact or shaker excitation). |
| OMA | Operational Modal Analysis — identifies modes from output-only operating data. |
| ODS | Operating Deflection Shape — the actual deformation pattern at a frequency or order under operation. |
| Mode shape | The characteristic deformation pattern of a structure at a natural frequency. |
| Damping ratio | How quickly a mode decays, expressed as a fraction of critical damping. |
| Stabilization diagram | A tool that plots identified poles vs. model order to separate physical modes from numerical ones. |