fl::audio::NoiseFloorTracker Class Reference

Detailed Description

NoiseFloorTracker maintains an adaptive estimate of the background noise floor for audio signals, with hysteresis to prevent "noise chasing" where the floor continuously adjusts to the signal level.

Features:

• Exponential decay: Floor gradually decreases toward minimum
• Slow attack: Floor increases slowly when signal is consistently low
• Hysteresis: Prevents rapid floor oscillations
• Cross-domain calibration: Combines time-domain (RMS) and frequency-domain metrics

How it works:

1. Track minimum observed signal level over time
2. Apply exponential decay to gradually lower the floor
3. If signal stays below floor + margin for sustained period, raise floor slowly
4. Use hysteresis to prevent the floor from chasing transient noise

Usage:

NoiseFloorTracker tracker;
NoiseFloorTrackerConfig config;
config.decayRate = 0.99f;
config.hysteresisMargin = 100.0f;
tracker.configure(config);
 
Sample sample = ...;
float rms = sample.rms();
tracker.update(rms);
 
float normalized = tracker.normalize(rms);  // Signal with floor removed
bool isAboveFloor = tracker.isAboveFloor(rms);

Definition at line 70 of file noise_floor_tracker.h.

#include <noise_floor_tracker.h>

Collaboration diagram for fl::audio::NoiseFloorTracker:

Classes
struct	Stats
	Get current statistics (for monitoring/debugging) More...

Public Member Functions
	NoiseFloorTracker () FL_NOEXCEPT
	NoiseFloorTracker (const NoiseFloorTrackerConfig &config) FL_NOEXCEPT
	~NoiseFloorTracker () FL_NOEXCEPT
void	configure (const NoiseFloorTrackerConfig &config) FL_NOEXCEPT
	Configure the noise floor tracker.
float	getFloor () const FL_NOEXCEPT
	Get current noise floor estimate.
const Stats &	getStats () const FL_NOEXCEPT
bool	isAboveFloor (float level) const FL_NOEXCEPT
	Check if signal is above noise floor + margin.
float	normalize (float level) const FL_NOEXCEPT
	Normalize signal by removing noise floor.
void	reset () FL_NOEXCEPT
	Reset noise floor to initial state.
void	update (float timedomainLevel, float frequencydomainLevel=-1.0f) FL_NOEXCEPT
	Update noise floor estimate with new observation.

Private Member Functions
float	combineDomains (float timeLevel, float freqLevel) const FL_NOEXCEPT
	Calculate combined metric from time and frequency domains.
void	updateFloor (float level) FL_NOEXCEPT
	Update floor estimate based on current observation.

Private Attributes
u32	mBelowFloorCount = 0
	Count of consecutive samples below floor (for slow attack)
NoiseFloorTrackerConfig	mConfig
float	mCurrentFloor = 100.0f
	Current noise floor estimate.
float	mLastHysteresisFloor = 0.0f
	Floor value at last hysteresis trigger Used to enforce hysteresis margin before allowing floor to rise.
Stats	mStats

Static Private Attributes
static constexpr u32	BELOW_FLOOR_THRESHOLD = 10
	Threshold for considering signal "consistently low".

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The documentation for this class was generated from the following files:

• fl/audio/noise_floor_tracker.h
• fl/audio/noise_floor_tracker.cpp.hpp