Large indoor arenas are hard to get right acoustically. Huge volumes, hard surfaces and long reverberation times can turn announcements and spoken events into noise. In this portfolio video, ALTA Integra presents speech acoustic modeling and auralization for the Gelora Bung Karno (GBK) Indoor Multipurpose Stadium in Jakarta. A 3D acoustic model of the arena predicts how sound behaves in the space, and auralization turns those results into audio, so architects, owners and stakeholders can hear how speech will sound from different seats before construction. The approach helps with decisions on absorptive finishes, reverberation control and sound system design, and supports speech intelligibility targets for sports, concerts, ceremonies and public events. It's for architects, acoustic and AV consultants, developers and venue operators working on large-volume, multipurpose spaces.