Overview

ST Sound Meter

Discussion

The SoundMeter converts a fract32 PCM signal into a logarithmic scale. Pre-filtering is possible with three different configurations (DC removal, A-weighting and C-weighting). Logarithmic conversion is then performed. A smoothing filter allows to average the log values with a configurable time constant. It supports three different sample rates, mono or stereo signal, with a maximum input frame size of 480 stereo samples.

Supported sample rates are: 8, 16, or 48 kHz.

The inspector shows the left and right levels in dB with a useful range of 0 to -90 dB.

Type Definition

typedef struct _ModuleSTSMR
{
    ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
    INT32 enable;                                 // Block enable
    INT32 averaging_time;                         // Smoothing time (0 - 10000) Ms
    INT32 filter_type;                            // Filter type (none, A weight, C weight, DC removal)
    FLOAT32 mean_level_left;                      // Measured left channel level
    FLOAT32 mean_level_right;                     // Measured right channel level
    INT32 nAPIResult;                             // Return status for last call into the ST API
    void * pGlobals;                              // Points to the global variables structure
} ModuleSTSMRClass;

Variables

Properties

Name	Type	Usage	isHidden	Default value	Range	Units
enable	int	parameter	0	1	0:1:1
averaging_time	int	parameter	0	1000	0:1:10000	msec
filter_type	int	parameter	0	0	Unrestricted
mean_level_left	float	state	0	0	-90:0
mean_level_right	float	state	0	0	-90:0
nAPIResult	int	state	1	1	Unrestricted
pGlobals	void *	const	1		Unrestricted

Pins

Input Pins

Name: in

Description: audio input

Data type: fract32

Channel range: 1, 2

Block size range: 96:480

Sample rate range: 8000, 16000, 48000

Complex support: Real

Output Pins

Name: out

Description: audio output

Data type: fract32

Scratch Pins

Channel count: 1

Block size: 96

Sample rate: 8000

MATLAB Usage

File Name: st_smr_module.m

 M = st_smr_module(NAME)
 Audio Weaver wrapper for the ST Sound Meter module.  Arguments:
   NAME - name of the module.
 Copyright (c) 2017 DSP Concepts, Inc.  All Rights Reserved.
 Author:  Chris Perry

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(8.D.2.4) STSMR