Effects of a transient noise reduction algorithm on speech intelligibility in noise, noise tolerance and perceived annoyance in cochlear implant users

Figures & data

Table 1. Stimuli and mean values of the characteristics of the transients used.

Type of stimuli	Type of transients	SPL peak (dB SPL)	# Transients/ second	Rise time (μs)	Duration (ms)	Type of continuous noise
Transients for speech-in-noise  tests	Clinking dishes, glasses etc.	95	1.0	675	134	Steady-state speech noise
Transients for ANL tests	Clinking dishes, glasses etc.	95	0.5	675	134	Steady-state speech noise
Kitchen sounds and exhaust noise	Clinking dishes, glasses etc.	97	1.6	933	147	Noise of an exhaust (65 dB SPL)
Hail on car window and car noise	Hail hits on car window	97	5.2	437	38	Car noise (72 dB SPL)
Hammering and machine noise	Hammering	96	2.0	1200	195	Noise of a sewing machine (63 dB SPL)
Steps with heels and babble	Steps with heels	97	2.0	1177	198	Babble noise 100p, near continuous  (67 dB SPL)

Duration is the time interval between the occurrence of transient peak level and a level 20 dB below this peak level.

Figure 1. Mean and 95% confidence intervals of per cent correct scores for the speech intelligibility in noise test for six conditions. The two light grey bars on the left show speech scores for speech without transients. The four dark grey bars show speech scores values for speech with transients. The annotations C1–C6 give the condition numbering. Several test conditions were compared and uncorrected p-values were shown. Asterisks denote that a difference is significant after correction for multiple comparisons. Dashed lines show the significance of differences due to TNR, solid lines show the significance of CNR effects, and dash-dotted lines show the significance of the effect of transients.

Figure 2. Mean and 95% confidence intervals of ANL values. The two light grey bars on the left show ANL values for speech without transients. The four dark grey bars show ANL values for speech with transients. The annotations C1–C6 give the condition numbering. Several test conditions were compared and uncorrected p-values were shown. Asterisks denote that a difference is significant after correction for multiple comparisons. Dashed lines show the significance of differences due to TNR, solid lines show the significance of CNR effects, and dash-dotted lines show the significance of the effect of transients.

Figure 3. Mean and 95% confidence intervals of the relative annoyance rating scores, derived from the paired-comparison data, for four different sounds. Each bar indicates the relative annoyance for a sound and test condition compared with the reference condition with TNR-off and CNR-off. For the mean of all sounds, asterisks indicate differences that were significant on the p < 0.05 level.