Signal Generators
Test signals for acoustic measurement — from continuous noise to impulse-based deconvolution
Choosing a Signal Type
AudioMap supports multiple signal types for different measurement scenarios. Continuous signals (Pink Noise) work with real-time transfer function analysis, while deterministic signals (MLS, ESS) enable impulse response extraction through deconvolution.
Pink Noise
DefaultEqual energy per octave, producing a -3 dB/octave slope on a linear frequency scale. The industry standard for audio system measurement because it approximates how we perceive loudness across frequency.
Tip: Pink noise is the go-to for most measurement workflows. It provides continuous excitation for real-time analysis and works with any analysis mode.
Sine Wave
Pure tone at a single frequency. Useful for testing specific frequencies, verifying driver response at crossover points, checking for distortion, and calibrating levels.
Tip: Use sine waves to verify individual driver operation and check for rattles or distortion at specific frequencies.
MLS
Maximum Length Sequence — a pseudo-random binary signal with a flat power spectrum and known autocorrelation properties. The impulse response is extracted by cross-correlating the captured signal with the original MLS sequence.
Note: MLS is sensitive to time-variance — any change in the system during measurement (e.g., moving people, temperature drift) can introduce artifacts.
ESS (Exponential Sine Sweep)
Recommended for IRA sine wave that sweeps exponentially from low to high frequency. Deconvolution with the inverse sweep produces a clean impulse response with harmonic distortion products separated in time, allowing them to be windowed out.
Tip: ESS gives the cleanest impulse response because harmonic distortion products arrive before the main impulse and can be discarded. Preferred for RT60 and reflection analysis.
Spatial Auto-Capture Process
Spatial auto-capture is AudioMap's automated capture workflow that measures both source and receiver simultaneously with a single trigger.
Arm
Select sources and configure generator
Generate
Signal output begins on trigger
Capture
Source reference and mic simultaneously recorded
Process
Transfer function computed from dual-channel data
Store
Measurement saved with metadata and position
Level Control
Generator Output Level
Controls the digital output level of the signal generator in dBFS. Set this to achieve optimal signal-to-noise ratio without clipping the amplifier or speakers.
Start at -20 dBFS and increase gradually. Monitor amplifier clip indicators and speaker excursion.
Signal-to-Noise Ratio
Higher generator levels improve SNR and coherence. The goal is to be at least 10 dB above the ambient noise floor across the measurement bandwidth.
Check coherence — consistently high coherence (above 0.9) indicates sufficient signal level.
Signal Type Comparison
| Feature | Pink Noise | Sine | MLS | ESS |
|---|---|---|---|---|
| Real-time TF | Yes | No | No | No |
| Impulse Response | No | No | Yes | Yes |
| Distortion Rejection | No | N/A | No | Yes |
| Time-Variance Tolerance | High | High | Low | Medium |
| SNR | Good | Best | Good | Excellent |
| Subjective Level | Moderate | Focused | Moderate | Low (swept) |