Sound Level Meter implementation that gives a result for each channel. A channel is the result of a filtered signal. More...

#include <lasp_slm.h>

Public Member Functions
	SLM (const d fs, const d Lref, const us downsampling_fac, const d tau, std::unique_ptr< Filter > pre_filter, std::vector< std::unique_ptr< Filter > > bandpass)
	Initialize a Sound Level Meter.

	~SLM ()

void	reset ()
	Reset state related to samples acquired. All filters reset to zero. Start again from no history.

	SLM (const SLM &o)=delete

SLM &	operator= (const SLM &o)=delete

	SLM (SLM &&o)=default

dmat	run (const vd &input)
	Run the sound level meter on given input data. Return downsampled level data for each filterbank channel.

vd	Lpeak () const
	Calculates peak levels measured for each filter channel. The peak level is just the highest instantaneous measured power value.

vd	Leq () const
	Calculates equivalent (time-averaged) levels measured for each filter channel.

vd	Lmax () const
	Calculates max levels measured for each filter channel. The max value is the maximum time-filtered (Fast / Slow) power level.

Static Public Member Functions
static SLM	fromBiquads (const d fs, const d Lref, const us downsampling_fac, const d tau, const vd &pre_filter_coefs, const dmat &bandpass_coefs)
	Convenience function to create a Sound Level meter from Biquad filters only.

static SLM	fromBiquads (const d fs, const d Lref, const us downsampling_fac, const d tau, const dmat &bandpass_coefs)
	Convenience function to create a Sound Level meter from Biquad filters only. No pre-filter, only bandpass.

static us	suggestedDownSamplingFac (const d fs, const d tw)
	Comput a 'suggested' downsampling factor, i.e. a lower frame rate at which sound level meter values are returned from the computation. This is possible since the signal power is low-pas filtered with a single pole low pass filter. It can remove computational burden, especially for plotting, to have a value > 10.

Public Attributes
vd	Pm
	Public storage for the mean of the square of the signal.

vd	Pmax
	Public storage for the maximum signal power, after single pole low-pass filter.

vd	Ppeak
	Storage for maximum computed signal power so far.

us	N = 0

Detailed Description

Sound Level Meter implementation that gives a result for each channel. A channel is the result of a filtered signal.

Definition at line 17 of file lasp_slm.h.

Constructor & Destructor Documentation

◆ SLM() [1/3]

SLM::SLM	(	const d	fs,
		const d	Lref,
		const us	downsampling_fac,
		const d	tau,
		std::unique_ptr< Filter >	pre_filter,
		std::vector< std::unique_ptr< Filter > >	bandpass
	)

Initialize a Sound Level Meter.

Counter for the number of time samples counted that came in;

Parameters

fs	Sampling frequency [Hz]
Lref	Level reference, used to scale to proper decibel units (dB SPL / dBV, etc)
downsampling_fac	Every 1/downsampling_fac value is returned from compute()
tau	Time consant of level meter
pre_filter	The pre-filter (Typically an A/C frequency weighting filter)
bandpass	The parallel set of bandpass filters.

Definition at line 15 of file lasp_slm.cpp.

◆ ~SLM()

SLM::~SLM ( )

Definition at line 50 of file lasp_slm.cpp.

◆ SLM() [2/3]

SLM::SLM ( const SLM & o )

delete

◆ SLM() [3/3]

SLM::SLM ( SLM && o )

default

Member Function Documentation

◆ fromBiquads() [1/2]

SLM SLM::fromBiquads	(	const d	fs,
		const d	Lref,
		const us	downsampling_fac,
		const d	tau,
		const dmat &	bandpass_coefs
	)

static

Convenience function to create a Sound Level meter from Biquad filters only. No pre-filter, only bandpass.

Parameters

fs	Sampling frequency [Hz]
Lref	Level reference, used to scale to proper decibel units (dB SPL / dBV, etc)
downsampling_fac	Every 1/downsampling_fac value is returned from compute()
tau	Time consant of level meter
bandpass_coefs	Biquad filter coefficients for bandpass filter. First axis isis the coefficient index, second axis is the filter index.

Returns: Sound Level Meter object

Definition at line 92 of file lasp_slm.cpp.

◆ fromBiquads() [2/2]

SLM SLM::fromBiquads	(	const d	fs,
		const d	Lref,
		const us	downsampling_fac,
		const d	tau,
		const vd &	pre_filter_coefs,
		const dmat &	bandpass_coefs
	)

static

Convenience function to create a Sound Level meter from Biquad filters only.

Parameters

fs	Sampling frequency [Hz]
Lref	Level reference, used to scale to proper decibel units (dB SPL / dBV, etc)
downsampling_fac	Every 1/downsampling_fac value is returned from compute()
tau	Time consant of level meter
pre_filter_coefs	Biquad filter coefficients for pre-filter
bandpass_coefs	Biquad filter coeffiecients for bandpass filter

Returns: Sound Level Meter object

Definition at line 83 of file lasp_slm.cpp.

◆ Leq()

vd SLM::Leq ( ) const

inline

Calculates equivalent (time-averaged) levels measured for each filter channel.

Returns: vector of equivalent level values

Definition at line 146 of file lasp_slm.h.

◆ Lmax()

vd SLM::Lmax ( ) const

inline

Calculates max levels measured for each filter channel. The max value is the maximum time-filtered (Fast / Slow) power level.

Returns: vector of max level values

Definition at line 153 of file lasp_slm.h.

◆ Lpeak()

vd SLM::Lpeak ( ) const

inline

Calculates peak levels measured for each filter channel. The peak level is just the highest instantaneous measured power value.

Returns: vector of peak level values

Definition at line 139 of file lasp_slm.h.

◆ operator=()

SLM & SLM::operator= ( const SLM & o )

delete

◆ reset()

void SLM::reset ( )

Reset state related to samples acquired. All filters reset to zero. Start again from no history.

Definition at line 193 of file lasp_slm.cpp.

◆ run()

dmat SLM::run ( const vd & input )

Run the sound level meter on given input data. Return downsampled level data for each filterbank channel.

Parameters

input Raw input data

Returns: Filtered level data for each filtered channel.

Definition at line 148 of file lasp_slm.cpp.

◆ suggestedDownSamplingFac()

us SLM::suggestedDownSamplingFac	(	const d	fs,
		const d	tw
	)

static

Comput a 'suggested' downsampling factor, i.e. a lower frame rate at which sound level meter values are returned from the computation. This is possible since the signal power is low-pas filtered with a single pole low pass filter. It can remove computational burden, especially for plotting, to have a value > 10.

Parameters

fs	Sampling frequency of signal [Hz]
tw	Time weighting of SLM low pass filter

Returns: Suggested downsampling factor, no unit. [-]

Definition at line 67 of file lasp_slm.cpp.

Member Data Documentation

◆ N

us SLM::N = 0

Definition at line 55 of file lasp_slm.h.

◆ Pm

vd SLM::Pm

Public storage for the mean of the square of the signal.

Storage for offset point in input arrays

Definition at line 43 of file lasp_slm.h.

◆ Pmax

vd SLM::Pmax

Public storage for the maximum signal power, after single pole low-pass filter.

Definition at line 48 of file lasp_slm.h.

◆ Ppeak

vd SLM::Ppeak

Storage for maximum computed signal power so far.

Public storage for the peak signal power, before single pole low-pass filter.

Definition at line 53 of file lasp_slm.h.

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

src/lasp/dsp/lasp_slm.h
src/lasp/dsp/lasp_slm.cpp

Public Member Functions

Static Public Member Functions

Public Attributes

Detailed Description

Constructor & Destructor Documentation

◆ SLM() [1/3]

◆ ~SLM()

◆ SLM() [2/3]

◆ SLM() [3/3]

Member Function Documentation

◆ fromBiquads() [1/2]

◆ fromBiquads() [2/2]

◆ Leq()

◆ Lmax()

◆ Lpeak()

◆ operator=()

◆ reset()

◆ run()

◆ suggestedDownSamplingFac()

Member Data Documentation

◆ N

◆ Pm

◆ Pmax

◆ Ppeak