Overview

Performs transfer function measurements

Discussion

This module will periodically output the stimulus signal. On the measurement side, the received signal of length L will be measured and averaged. The number of times that the stimulus signal is output and the received signal measured is numReps. The average of the recorded signal is in the response buffer. The number of times to repeat the stimulus before starting the acquisition is the numPreCycles. The trigger is a parameter which the PC sets to trigger the measurement. This will initially be 0 (waiting), then set to 1 by PC (start measurement). Once the measurement is completed, it will be set to 0.

This module can be controlled and the response analyzed either with the built in inspector GUI, or using MATLAB if the user has the Pro edition of Designer.

To use the inspector, double-click the module on the canvas to launch and manage the measurement process

Follow these steps to plot the measurement in MATLAB. (Note: This requires AWE Designer Pro Edition)

Run the layout in Designer.
Start a measurment using the module's inspector.
Get the running layouts structure in Matlab:
```
>> GSYS = get_gsys();
```

Next read out the stimulus and response in Matlab command window:

>> x = GSYS.SYS.MeasurementV21.response;
>> z = GSYS.SYS.MeasurementV21.stimulus;

Next compute the transfer function and plot it. For example, if you have the signal processing toolbox you can do:
```
>>[tf, f] = tfestimate(z,x,[],[],[],48000);
>> plot(f,abs(tf));shg
```

Type Definition

typedef struct _ModuleMeasurementV2
{
    ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
    INT32 L;                                      // Length of the stimulus signal.
    INT32 numReps;                                // Number of times to repeat the stimulus and average the result
    INT32 numPreCycles;                           // Number of times to repeat the stimulus before starting the acquisition
    INT32 trigger;                                // state variable/parameter which the PC sets to trigger the measurement.
    INT32 readIndex;                              // Index used for circular reading
    INT32 stateIndex;                             // Index used for state
    INT32 cnt;                                    // Index used to measure the response
    FLOAT32* stimulus;                            // Column vector of length L holding the stimulus signal
    FLOAT32* response;                            // Holds the time average measured signal
} ModuleMeasurementV2Class;

Variables

Properties

Name	Type	Usage	isHidden	Default value	Range	Units
L	int	const	0	16380	Unrestricted
numReps	int	parameter	0	16	1:1024
numPreCycles	int	parameter	0	2	1:4
trigger	int	parameter	0	0	0:1
readIndex	int	state	1	0	Unrestricted
stateIndex	int	state	1	0	Unrestricted
cnt	int	state	1	0	Unrestricted
stimulus	float*	parameter	0	[16384 x 1]	Unrestricted
response	float*	derived	0	[1 x 16384]	Unrestricted

Pins

Input Pins

Name: measure

Description: measured audio input

Data type: float

Channel range: Unrestricted

Block size range: Unrestricted

Sample rate range: Unrestricted

Complex support: Real

Output Pins

Name: stimulus

Description: stimulus output

Data type: float

MATLAB Usage

File Name: measurement_v2_module.m

 M=measurement_v2_module(NAME, L, enableTriggerPin)
 Audio Weaver module which performs transfer function measurements 
 using a stimulus and response.  The module outputs the stimulus signal
 and averages the response over multiple repetitions.  Arguments:
    NAME - name of the module
    L - length of the measurement signal, in samples