A system for generating virtual room acoustics with low-latency response and immersive surround sound with height is described. The system has been primarily developed for shared reality applications in distance music teaching and collaboration, where low-latency is required for successful interactive communication between distant participants. It is also used in a sophisticated recording and performance studio where artists can rehearse, perform and be recorded in virtual acoustics of rooms measured in other locations. The method of reconstructive acoustics uses specifically captured multichannel high-resolution impulse responses (IR) of the original concert halls, in multiples of six. To ensure a detailed characterization of the diffuse field of a room, the excitation of the room is done with a distributed sound source whose power response is flat across almost all frequencies within the audible range. High acoustic power output of the source used to excite the room and slow-swept sine wave stimulus ensure wide dynamic range of the captured impulse responses approaching 120 dB. The room response is recorded in four layers of 6 microphone channels, each layer at a different elevation, all later convolved with the direct signal and projected around and above the performer using four layers of surround loudspeakers. The convolution process uses dedicated signal processing hardware capable of 6 real-time convolutions of 15- seconds-long IRs with 10 ms latency. Time-variant impulse responses can be rendered using overlapping convolutions. The goal is to provide the performer with the most representative interpretation of the room that can best approximate the subjective impression of the original space. Examples will be given describing virtual acoustic spaces developed to make recordings of Haydn's fortepiano and harpsichord sonatas for the upcoming SA-CD release.
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