An exploratory investigation of speech recognition thresholds in noise with auralisations of two reverberant rooms

Figures & data

Figure 1. Outline of the auralisation procedure (see Section 2.1. for more details). A complete description of the Spatial Decomposition Method (SDM) has been described by Tervo et al. (2013). The panoramic photo of the listening room is adapted from Ojansivu (2017).

Table 1. T₂₀, C₅₀, IACCE3/L3, STI and D/R values for each room.

	T20	C50	IACC E3/L3	STI	D/R	RR
Room 1	0.9 s	9.8 dB	0.97/0.21	0.85	9.2 dB	2.0 m
Room 2	1.8 s	4.1 dB	0.78/0.29	0.72	1.4 dB	1.3 m

T₂₀ is the reverberation time. C₅₀ is calculated as the ratio of the early (0 and 50 ms) and late (after 50 ms) sound energies. IACC is the interaural cross-correlation coefficient averaged over 500, 1000 and 2000 Hz for the early (0–50 ms; E3) and late (50 msl L3) reverberations. T₂₀ and C₅₀ values are averaged over 250, 500, 1000 and 2000 Hz octave bands. D/R values are calculated from RIRs as wideband sound energy ratio with a direct sound window of 5 ms. RR refers to an estimated reverberation radius. See Section 2.2. for more details.

Figure 2. Hearing thresholds of all individual participants (grey lines) and the average thresholds of normal-hearing (NH; PTA < 25 dB HL) and hearing-impaired (HI; PTA ≥ 25 dB HL) groups. The pure-tone average (PTA) scores are calculated as the average over both ears and at 500, 1000, 2000 and 4000 Hz frequencies. The individual lines have been horizontally displaced to improve their visibility in the figure.

Figure 3. (a) Normal hearing: Averages and standard deviations per test condition. (b) Hearing-impaired: Median and the 25th and 75th percentiles per test condition. Whiskers extend maximally to 1.5 times the inter-quartile range. (c) Pure-tone average (PTA; 500–4000 Hz; both ears) scores plotted against the SRT results for each test condition. The vertical dotted line depicts the 25 dB HL PTA cut-off for normal hearing. Ref: Grey squares; Room 1: Red points; Room 2: Blue crosses.

Figure 4. Hearing aid benefits per individual and test condition.

Figure 5. Modulation transfer ratios for each room and SNRs of 0, −5 and −10 dB. The values are calculated by using RIRs and a single randomly selected sentence from the Finnish Matrix Sentence Test.

Tervo, Sakari, Jukka Pätynen, Antti Kuusinen, and Tapio Lokki. 2013. “Spatial decomposition method for room impulse responses.” Journal of the Audio Engineering Society, 61 (1/2): 17–28.

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Ojansivu, Tuukka. 2017. “Realistinen ¨äaniymp¨aris¨o kuulontutkimuksiin (engl. A realistic listening environment for audiometry).” Bachelor Thesis, Metropolia University of Applied Sciences https://www.theseus.fi/bitstream/handle/10024/125480/Ojansivu.Tuukka.pdf.

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Data availability statement

The data that support the findings of this study are available on request from the corresponding author, A.K. The data are not publicly available due to the nature of this study.