Acoustics of karst tourist caves: a case study in Guizhou Province, China

The acoustic environment of karst tourist caves significantly impacts visitor experience and the effectiveness of information dissemination, yet systematic studies on their acoustics remain scarce. This study investigates the acoustic properties of a representative karst tourist cave in Guizhou Province, China, by combining in-situ measurements with 3D laser scanning. Impulse responses were systematically recorded at 22 positions across six caverns, and key parameters-including reverberation time (T₂₀), early decay time (EDT), definition (D₅₀), clarity (C₈₀), and speech transmission index (STI)-were analyzed in relation to spatial geometries obtained from 3D scans. The results reveal substantial spatial variations in acoustic conditions: mid-frequency T₂₀ ranges from 1.4 s to 3.1 s, largely governed by cavern volume, geometry, and entrance-related attenuation. The average EDT/T₂₀ ratio is 0.70, indicating non-uniform early decay behavior. While D₅₀ values are relatively consistent (0.49-0.74), C₈₀ shows greater variability (1.86-6.89 dB), both influenced by spatial complexity. Furthermore, significant correlations exist between STI and other parameters (P < 0.01), confirming that reverberation control and early-energy enhancement are crucial for improving speech intelligibility. These findings provide a scientific basis for acoustic optimization in show caves, supporting better guided tours and safety communications.