Prior listening in rooms improves speech intelligibility

Abstract

Although results from previous studies have demonstrated that the acoustic effects of a single reflection are perceptually suppressed after repeated exposure to a particular configuration of source and reflection, the extent to which this dynamic echo suppression might generalize to speech understanding in room environments with multiple reflections and reverberation is largely unknown. Here speech intelligibility was measured using the coordinate response measure corpus both with and without prior listening exposure to a reverberant room environment, which was simulated using virtual auditory space techniques. Prior room listening exposure was manipulated by presenting either a two-sentence carrier phrase that preceded the target speech, or no carrier phrase within the room environment. Results from 14 listeners indicate that with prior room exposure, masked speech reception thresholds were on average 2.7 dB lower than thresholds without exposure, an improvement in intelligibility of over 18 percentage points on average. This effect, which is shown to be absent in anechoic space and greatly reduced under monaural listening conditions, demonstrates that prior binaural exposure to reverberant rooms can improve speech intelligibility, perhaps due to a process of perceptual adaptation to the acoustics of the listening room.

Figure 1

Room dimensions and the position of the listener, the speech target, and the noise masker for all simulated rooms

Figure 2

Examples of the target and masker waveforms (left-ear only) for the NC and SC conditions in a moderately reverberant room (R2).

Figure 3

Proportion of correct responses, P(C), as a function of signal-to-noise ratio for a single listener (LIS) in Exp. I. Data from the moderately reverberant room (R2) for both the NC and SC conditions are shown, along with logistic function fits for each condition (see text for details). Each data point is based on responses from 30 trials. Speech reception threshold estimates and their 95% confidence intervals are indicated for each curve at the midpoint between chance and perfect performance.

Figure 4

Speech reception thresholds from Exp. I for the NC and SC conditions in room R2. 95% confidence intervals are displayed for each threshold estimate. Listeners are rank-ordered from left to right by effect size (NC threshold–SC threshold). Threshold values based on function fits to the data pooled across all listeners are shown on the right.

Figure 5

Speech reception thresholds from Exp. II for the NC and SC conditions in anechoic space (R0). 95% confidence intervals are displayed for each threshold estimate. The left to right listener order is the same as shown in Fig. 4, except that listener LIT did not participate in Exp. II. Threshold values based on function fits to the data pooled across all listeners are shown on the right.

Figure 6

Speech reception thresholds from Exp. III for the NC and SC conditions in R2 under monaural listening conditions (left-ear only). 95% confidence intervals are displayed for each threshold estimate. The left to right listener order is the same as shown in Fig. 4. Threshold values based on function fits to the data pooled across all listeners are shown on the right.