SSMS Test

In an SSMS (Single Stimulus Mixed Source) Test three samples are played and the level of one sample is altered. The sample S1 is stereo background noise. Sample S2 is mono noise and sample S3 is a mono speech sample. Sample S3's level is controlled by the subject and its output is mixed together with the right output channel. The test can also be configured so that the variable gain controls both S2 and S3 or only S2.

Here is a list of parameters needed by the test. This table lists only the parameters that have some special information about parameters or that override or adds new parameters to the common test parameters list.

Parameter Value Description R/O

class SSMS A class alias (SSMS) or a fully qualified java class name (guinea.logic.SSMSTest) of the class that handles the SSMS test. Req.

Parameter	Value	Description	R/O
class	SSMS	A class alias (SSMS) or a fully qualified java class name (guinea.logic.SSMSTest) of the class that handles the SSMS test.	Req.

The SSMS has some special parameters. Prepend parameter names with 'SSMS.' string, for example:

   # set level of sample S1
   SSMS.S1Volume=-10dB

Here is the list:

Parameter Value Description R/O

S1Volume Volume level Se the volume of the sample S1. The volume level can be given in linear, decibel or percent scale. The default is to use the sample's inherent level (level is 0dB (decibel) or 1.0 (linear)). Opt.

S2Volume Volume level Se the volume of the sample S2. It is used to set the constrant gain for S2 or it is it's initial gain if variable gain is used for this signal. Opt.

S3Volume Volume level Se the volume of the sample S3. It is used to set the constrant gain for S3 or it is it's initial gain if variable gain is used for this signal. Opt.

monochannel channel index To which output channel to direct the output of the mono samples S1 and S2. Default is 1 (right), 0 would be left. Opt.

ensureNoOverflows true or false Limit output volume so that no overflows should occur when many samples are played together. Opt.

scaleMax Volume level The maximum on the scale that the subject uses for setting the level of samples S2 and S3. This is used to avoid overflows. The default is that the maximum of the scale is 0dB (1.0 linear). This parameter has no effect when ensureNoOverflows is false. Opt.

levelControlName questionID The question ID that is also used to control the level of the S2 and S3 samples. Default is 'level'. Opt.

levelControlsSignals list of signals Specify which signals the level (gain) controller controls. By default it is 'S3' (variable gain for S3, constrant gain for S2). Multiple signals are specified with a comma-separated list of signal names, for example, the list 'S2,S3' tells the gain controller to set the gain for both S2 and S3. Opt.

Parameter	Value	Description	R/O
S1Volume	Volume level	Se the volume of the sample S1. The volume level can be given in linear, decibel or percent scale. The default is to use the sample's inherent level (level is 0dB (decibel) or 1.0 (linear)).	Opt.
S2Volume	Volume level	Se the volume of the sample S2. It is used to set the constrant gain for S2 or it is it's initial gain if variable gain is used for this signal.	Opt.
S3Volume	Volume level	Se the volume of the sample S3. It is used to set the constrant gain for S3 or it is it's initial gain if variable gain is used for this signal.	Opt.
monochannel	channel index	To which output channel to direct the output of the mono samples S1 and S2. Default is 1 (right), 0 would be left.	Opt.
ensureNoOverflows	true or false	Limit output volume so that no overflows should occur when many samples are played together.	Opt.
scaleMax	Volume level	The maximum on the scale that the subject uses for setting the level of samples S2 and S3. This is used to avoid overflows. The default is that the maximum of the scale is 0dB (1.0 linear). This parameter has no effect when ensureNoOverflows is false.	Opt.
levelControlName	questionID	The question ID that is also used to control the level of the S2 and S3 samples. Default is 'level'.	Opt.
levelControlsSignals	list of signals	Specify which signals the level (gain) controller controls. By default it is 'S3' (variable gain for S3, constrant gain for S2). Multiple signals are specified with a comma-separated list of signal names, for example, the list 'S2,S3' tells the gain controller to set the gain for both S2 and S3.	Opt.

Overflow avoidance

This test can try to avoid any overflows when many samples are mixed together. In SSMS test case, three samples S1, S2 and S3 are playing at the same time and they are all added together. If all samples have full range, overflows are bound to occur. The SSMS test tries to avoid overflows so that it limits the MCL level that can be set. If all samples S1-3 have max volumes set to 1.0 (0dB), to maximum level they together can be 3.0 (+9.5dB). The output level scale is then limited to 1/3 (-9.5dB) so that the digital output level never goes to more than 1.0 (0dB).

Test item parameters

The test items used in SSMS test have three parameters S1, S2 and S3 which are sample IDs of samples.

Parameter Value Description R/O

S1 sample ID Sample ID of the S1 sample. It is a stereo background noise sample. Req.

S2 sample ID Sample ID of the S2 sample. It is a mono noise sample. Req.

S3 sample ID Sample ID of the S3 sample. It is a mono speech sample. Req.

Parameter	Value	Description	R/O
S1	sample ID	Sample ID of the S1 sample. It is a stereo background noise sample.	Req.
S2	sample ID	Sample ID of the S2 sample. It is a mono noise sample.	Req.
S3	sample ID	Sample ID of the S3 sample. It is a mono speech sample.	Req.

Here is an example of an SSMS item:

   # which sample is the S1 sample
   item1.S1=tausta1
   # which sample is the S2 sample
   item1.S2=noise1
   # which sample is the S3 sample
   item1.S3=crapachi

The items itemID is 'item1'.

Results

As a result a volume level is stored.

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Last modified: Wed Jan 20 11:43:52 EET 1999