3M SE, DL user manual STI-PA modulation screen, STI-PA Modulation screen

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Speech Intelligibility

STI-PA results screens

STI-PA modulation screen

In the Modulation measurement screen, the average decibel level over the run- time in seven octave bands ranging from 125HZ to 8KHz with 14 frequencies is displayed in a tabular format. These values are the signal to noise ratio (accounts for any interfering background noise such as non-linear distortions, electronics, reverberation, HVAC systems) in each attenuation band and indicates which values are intelligible/unintelligible based on the CIS/STI scale.

NOTE: A high MTF value indicates that the listeners received the message without any distortions or interference.

LEQ

Average dB level in band

Signal to noise ratio for each band * Based on the CIS/STI scale ranging from 0.00 – 1.00

Figure 6-22: STI-PA Modulation screen

Table 6-4 defines the STI-PA: modulation frequencies for the seven octave bands (per the IEC 60268-16 standard).

Octave band Hz		125-250	500	1 k	2 k	4 k	8 k
First modulation		1.00	.63	2.00	1.25	0.80	2.50
frequency	Hz
Second modulation		5.00	3.15	10.0	6.25	4.00	12.5
frequency	Hz

Table 6-5 defines the STI octave band with specific male and female weighting

Octave band Hz	STI	- 125-measurements250 500		1 k	the2 kIEC	4 k	16	stan8 k	dard).
Males		0.127	0.23	0.23	0.30	0.224		0.17
			0	3	9			3
		0.078	0.06	0.01	0.04	0.095		-
			5	1	7
Females		0.117	0.22	0.21	0.32	0.250		0.19
			3	6	8			4
		0.099	0.06	0.06	0.02	0.076		-
			6	2	5

Models SE and DL