Measuring the Acoustical Properties of the BBC Maida Vale Recording Studios for Virtual Reality
2. BBC Maida Vale Recording Studios
2.2. Studio Dimensions and Characteristics
3. Acoustic Measurements
3.1. Impulse Response Capture
3.2. Methodology and Instrumentation
3.3. Practical Measurement
3.3.1. MV2 and MV3 Measurement Phases
- MV2/MV3 Virtual Reality Capture:5 Genelec 8040a sources, representing sources at typical recording positions were set up on a stage area, at points labelled PA1 to PA5 (PA stands for Performance Area), all at 1.5 m height to tweeter. A grid of 16 receiver points, labelled OA1-16 (OA stands for Outside performance Area) were set up, each 3 m apart. The Eigenmike and reference omninidirectional microphone were measured at each of these points at a height of 1.7 m. Both were north facing. No sitting audience positions were captured in the studios due to time constraints.
- MV2/MV3 ISO-3382 Capture:Referring to Figure 5, an additional two source points at PA6 and PA7 were set for the ISO measurements. Receiver locations for the these measurements were at OA1, OA6 and OA14. The Eigenmike, reference lav and a KEMAR binaural manikin were measured at these positions. The Eigenmike was at 1.7 m height and KEMAR was set to 1.5 m height to the ear canal, which is in range for the typical heights of UK men (175 cm) and women (161 cm)  with consideration of ear canal offset. Both were north-facing.For MV2, points OA13 to OA16 were 3.29 m from the back wall (distance g). The grid spacing was 2.5 m (distances c, d, e and f). Line PA1–PA3 was 2 m from line PA4–PA6 (distance c). Dodecahedron point PA7 was 4 m from PA2 (distance b). Dodecahedron point PA6 was 1.25 m from PA5 (distance a). Width (W) is 13.69 m and length (L) is 21.96 m.For MV3, the line of points OA13 to OA16 were 4.3 m from the back wall (distance g). Grid spacing was 1.5 m between points (distances c, d, e and f).Dodecahedron point PA7 was 3 m from PA2 (distance b). Dodecahedron point PA6 was 0.75 m from PA5 (distance a). Width (W) is 13.38 m and length (L) is 22.69 m.
3.3.2. MV4 Measurement Phase
- MV4 Virtual Reality Capture: This was the largest measurement phase of all studios. Four performer positions were defined, with three sources representing performers at 1.5 m height and a fourth position representing a drum kit. These positions are labelled PA3, PA11, PA15 and PA23 as shown in Figure 6. The drummer position consists of 4 sources, representing a triangular spread of drums and a kick drum at point PA9, PA11, PA19 and PA12 respectively. The triangular configuration covering the drum area allows for IR interpolation to be undertaken to more clearly define drum source positions for any given virtual drum kit.Impulse responses using the Eigenmike were captured at each performer position, including simultaneous source–receiver points. This was to facilitate foldback of a musician’s own acoustic within the virtual space, i.e., when they perform, they should hear back the room response to their own performance at their performance position. Consequently, for these measurements, the Eigenmike was placed 2 cm above the Genelecs. Care was taken to ensure that the signal did not distort. However a noticeable low frequency boost was captured due to the off-axis (on top) position of the Eigenmike relative to the loudspeaker and the proximity of the transducers. This effect was removed in post-processing.For 6DoF-enabled measurements, the receiver area was extended in between the performers to a grid of 25 measurement points, equally spaced 1 m apart. An additional 20 measurement points were captured outside of the performance area (OA points) to facilitate audience perspective. These include points on the main studio floor as well as on the upper balcony. All receiver points are at a height of 1.5 m, with the exception of PA11 (drummer position), which is at a height of 1.2 m. Full coordinates of each datapoint are available in the online database.
- MV4 ISO-3382 measurements: The NTI dodecahedron loudspeaker was again used for measurements at points PA5, PA13 and PA23. Three receiver positions on the lower level (OA2, OA7 and OA13) and three positions on the upper level (OA15, OA16 and OA20) were utilised. Both the Eigenmike and KEMAR were again used to capture the ISO measurements and were both north-facing, with heights of 1.6 m. The dodecahedron was at a height of 1.5 m.
- MV4 Performer Reference Positions: The KEMAR binaural head utilised in these sessions also includes a voice box (model GRAS 45BC). Measurements were taken by running an equalised sweep through the voice box and capturing the returning room acoustic at the manikin’s ears. Equalisation for this sweep was performed in the anechoic chamber at the University of York . This gives an excellent reference for understanding the self-direct-to-reverberant ratio as experienced at each performer position. It also provides a calibration level for performer-direct sound-to-reverberation auralisation in the virtual environment. The four performer positions were measured for this setup. KEMAR faced PA13 in each measurement.
3.3.3. MV5 Measurement Phase
- MV5 VR Capture: MV5 consisted of 12 measurement points altogether, as shown in Figure 7. Two performer positions were defined at PA3A, set 1.5 m into the room with a height of 1.5 m, and PA7B, set 5 m into the room at a height of 1 m. As the studio is often used to record intimate acoustic guitar or piano performances, these points were augmented with further measurements to simulate these instruments. Points PA7A and PA7C were included for simulation of a piano (at a height of 1.2 m), and points 3B and 7C were included to simulate acoustic guitars (at a height of 1 m). The Eigenmike was set to 1.6 m and faced east for all measurements.
- MV5 ISO-3382 Capture: The docecahedron was set to a height of 1.5 m. For ISO-3382, two source–receiver combinations were captured. First with the dodecahedron loudspeaker at PA3A and receivers at PA4, PA5, PA6 and PA7B. Second, with the dodecahedtron at PA6, with receivers PA7B, PA3A, PA4 and PA5. The Eigenmike was set to 1.7 m facing east and KEMAR to 1.5 m facing south.
- MV5 Performer Reference Positions: Similar to MV4, reference measurements were captured at each of the performer positions using 5 Genelec loudspeakers and the KEMAR binaural head with voicebox as the sources. The in-ear microphones of the KEMAR were used as receivers. KEMAR was positioned at PA3A and PA7B for these measurements, facing south then north, respectively, at a height of 1.5 m.
4. Data Post-Processing
4.1. Data Extraction and Cleanup
4.2. Data Parsing and Transcoding
5.1. Acoustic Comparison
5.2. Vr Rendering
6. Database of Measurements
- 32-Channel Eigenmike capsule impulse responses (RAW);
- 32-Channel Eigenmike capsule impulse responses (Diffuse Field Equalised);
- 16-channel third-order Ambisonic Impulse Responses;
- 2-channel KEMAR impulse Responses (RAW);
- 2-channel KEMAR impulse Responses (Diffuse Field Equalised);
- Mono Reference omnidirectional microphone impulse responses (RAW);
- Mono Reference omnidirectional microphone impulse responses (Diffuse Field Equalised).
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
|ESS||Exponential Sinetone Sweep|
|DFE||Diffuse Field Equalised|
|HOA||Higher Order Ambisonic|
|KEMAR||Knowles Electronic Manikin for Acoustic Research|
|OA||Outside performance Area|
|RIR||Room Impulse Response|
|SRIR||Spatial Room Impulse Response|
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|Measurement Phase||Loudspeaker||Receivers||Recording Device|
|VR||7 × Genelec 8040A||Eigenmike,|
Fireface UFX II,
|ISO-3382||NTI DS3 Dodecahedron||Eigenmike,|
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Kearney, G.; Daffern, H.; Cairns, P.; Hunt, A.; Lee, B.; Cooper, J.; Tsagkarakis, P.; Rudzki, T.; Johnston, D. Measuring the Acoustical Properties of the BBC Maida Vale Recording Studios for Virtual Reality. Acoustics 2022, 4, 783-799. https://doi.org/10.3390/acoustics4030047
Kearney G, Daffern H, Cairns P, Hunt A, Lee B, Cooper J, Tsagkarakis P, Rudzki T, Johnston D. Measuring the Acoustical Properties of the BBC Maida Vale Recording Studios for Virtual Reality. Acoustics. 2022; 4(3):783-799. https://doi.org/10.3390/acoustics4030047Chicago/Turabian Style
Kearney, Gavin, Helena Daffern, Patrick Cairns, Anthony Hunt, Ben Lee, Jacob Cooper, Panos Tsagkarakis, Tomasz Rudzki, and Daniel Johnston. 2022. "Measuring the Acoustical Properties of the BBC Maida Vale Recording Studios for Virtual Reality" Acoustics 4, no. 3: 783-799. https://doi.org/10.3390/acoustics4030047